Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

10 files changed, 6468 insertions, 0 deletions

diff --git a/gfx/wr/webrender_api/src/channel.rs b/gfx/wr/webrender_api/src/channel.rs
new file mode 100644
index 0000000000..7d21c6e433
--- /dev/null
+++ b/gfx/wr/webrender_api/src/channel.rs
@@ -0,0 +1,180 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::{Epoch, PipelineId};
+use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use std::io::{self, Cursor, Error, ErrorKind, Read};
+use std::mem;
+
+pub use crossbeam_channel as crossbeam;
+
+#[cfg(not(target_os = "windows"))]
+pub use crossbeam_channel::{Sender, Receiver};
+
+#[cfg(target_os = "windows")]
+pub use std::sync::mpsc::{Sender, Receiver};
+
+#[derive(Clone)]
+pub struct Payload {
+    /// An epoch used to get the proper payload for a pipeline id frame request.
+    ///
+    /// TODO(emilio): Is this still relevant? We send the messages for the same
+    /// pipeline in order, so we shouldn't need it. Seems like this was only
+    /// wallpapering (in most cases) the underlying problem in #991.
+    pub epoch: Epoch,
+    /// A pipeline id to key the payload with, along with the epoch.
+    pub pipeline_id: PipelineId,
+    pub display_list_data: Vec<u8>,
+}
+
+impl Payload {
+    /// Convert the payload to a raw byte vector, in order for it to be
+    /// efficiently shared via shmem, for example.
+    /// This is a helper static method working on a slice.
+    pub fn construct_data(epoch: Epoch, pipeline_id: PipelineId, dl_data: &[u8]) -> Vec<u8> {
+        let mut data = Vec::with_capacity(
+            mem::size_of::<u32>() + 2 * mem::size_of::<u32>() + mem::size_of::<u64>() + dl_data.len(),
+        );
+        data.write_u32::<LittleEndian>(epoch.0).unwrap();
+        data.write_u32::<LittleEndian>(pipeline_id.0).unwrap();
+        data.write_u32::<LittleEndian>(pipeline_id.1).unwrap();
+        data.write_u64::<LittleEndian>(dl_data.len() as u64)
+            .unwrap();
+        data.extend_from_slice(dl_data);
+        data
+    }
+    /// Convert the payload to a raw byte vector, in order for it to be
+    /// efficiently shared via shmem, for example.
+    pub fn to_data(&self) -> Vec<u8> {
+        Self::construct_data(self.epoch, self.pipeline_id, &self.display_list_data)
+    }
+
+    /// Deserializes the given payload from a raw byte vector.
+    pub fn from_data(data: &[u8]) -> Payload {
+        let mut payload_reader = Cursor::new(data);
+        let epoch = Epoch(payload_reader.read_u32::<LittleEndian>().unwrap());
+        let pipeline_id = PipelineId(
+            payload_reader.read_u32::<LittleEndian>().unwrap(),
+            payload_reader.read_u32::<LittleEndian>().unwrap(),
+        );
+
+        let dl_size = payload_reader.read_u64::<LittleEndian>().unwrap() as usize;
+        let mut built_display_list_data = vec![0; dl_size];
+        payload_reader
+            .read_exact(&mut built_display_list_data[..])
+            .unwrap();
+
+        assert_eq!(payload_reader.position(), data.len() as u64);
+
+        Payload {
+            epoch,
+            pipeline_id,
+            display_list_data: built_display_list_data,
+        }
+    }
+}
+
+pub type PayloadSender = MsgSender<Payload>;
+
+pub type PayloadReceiver = MsgReceiver<Payload>;
+
+pub struct MsgReceiver<T> {
+    rx: Receiver<T>,
+}
+
+impl<T> MsgReceiver<T> {
+    pub fn recv(&self) -> Result<T, Error> {
+        self.rx.recv().map_err(|e| io::Error::new(ErrorKind::Other, e.to_string()))
+    }
+
+    pub fn to_crossbeam_receiver(self) -> Receiver<T> {
+        self.rx
+    }
+}
+
+#[derive(Clone)]
+pub struct MsgSender<T> {
+    tx: Sender<T>,
+}
+
+impl<T> MsgSender<T> {
+    pub fn send(&self, data: T) -> Result<(), Error> {
+        self.tx.send(data).map_err(|_| Error::new(ErrorKind::Other, "cannot send on closed channel"))
+    }
+}
+
+pub fn payload_channel() -> Result<(PayloadSender, PayloadReceiver), Error> {
+    let (tx, rx) = unbounded_channel();
+    Ok((PayloadSender { tx }, PayloadReceiver { rx }))
+}
+
+pub fn msg_channel<T>() -> Result<(MsgSender<T>, MsgReceiver<T>), Error> {
+    let (tx, rx) = unbounded_channel();
+    Ok((MsgSender { tx }, MsgReceiver { rx }))
+}
+
+///
+/// These serialize methods are needed to satisfy the compiler
+/// which uses these implementations for the recording tool.
+/// The recording tool only outputs messages that don't contain
+/// Senders or Receivers, so in theory these should never be
+/// called in the in-process config. If they are called,
+/// there may be a bug in the messages that the replay tool is writing.
+///
+
+impl<T> Serialize for MsgSender<T> {
+    fn serialize<S: Serializer>(&self, _: S) -> Result<S::Ok, S::Error> {
+        unreachable!();
+    }
+}
+
+impl<'de, T> Deserialize<'de> for MsgSender<T> {
+    fn deserialize<D>(_: D) -> Result<MsgSender<T>, D::Error>
+                      where D: Deserializer<'de> {
+        unreachable!();
+    }
+}
+
+/// A create a channel intended for one-shot uses, for example the channels
+/// created to block on a synchronous query and then discarded,
+#[cfg(not(target_os = "windows"))]
+pub fn single_msg_channel<T>() -> (Sender<T>, Receiver<T>) {
+    crossbeam_channel::bounded(1)
+}
+
+/// A fast MPMC message channel that can hold a fixed number of messages.
+///
+/// If the channel is full, the sender will block upon sending extra messages
+/// until the receiver has consumed some messages.
+/// The capacity parameter should be chosen either:
+///  - high enough to avoid blocking on the common cases,
+///  - or, on the contrary, using the blocking behavior as a means to prevent
+///    fast producers from building up work faster than it is consumed.
+#[cfg(not(target_os = "windows"))]
+pub fn fast_channel<T>(capacity: usize) -> (Sender<T>, Receiver<T>) {
+    crossbeam_channel::bounded(capacity)
+}
+
+/// Creates an MPMC channel that is a bit slower than the fast_channel but doesn't
+/// have a limit on the number of messages held at a given time and therefore
+/// doesn't block when sending.
+#[cfg(not(target_os = "windows"))]
+pub use crossbeam_channel::unbounded as unbounded_channel;
+
+
+#[cfg(target_os = "windows")]
+pub fn fast_channel<T>(_cap: usize) -> (Sender<T>, Receiver<T>) {
+    std::sync::mpsc::channel()
+}
+
+#[cfg(target_os = "windows")]
+pub fn unbounded_channel<T>() -> (Sender<T>, Receiver<T>) {
+    std::sync::mpsc::channel()
+}
+
+#[cfg(target_os = "windows")]
+pub fn single_msg_channel<T>() -> (Sender<T>, Receiver<T>) {
+    std::sync::mpsc::channel()
+}
diff --git a/gfx/wr/webrender_api/src/color.rs b/gfx/wr/webrender_api/src/color.rs
new file mode 100644
index 0000000000..f19f83bb3d
--- /dev/null
+++ b/gfx/wr/webrender_api/src/color.rs
@@ -0,0 +1,160 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use peek_poke::PeekPoke;
+use std::cmp;
+use std::hash::{Hash, Hasher};
+
+/// Represents pre-multiplied RGBA colors with floating point numbers.
+///
+/// All components must be between 0.0 and 1.0.
+/// An alpha value of 1.0 is opaque while 0.0 is fully transparent.
+///
+/// In premultiplied colors transitions to transparent always look "nice"
+/// therefore they are used in CSS gradients.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, PartialOrd, Serialize)]
+pub struct PremultipliedColorF {
+    pub r: f32,
+    pub g: f32,
+    pub b: f32,
+    pub a: f32,
+}
+
+#[allow(missing_docs)]
+impl PremultipliedColorF {
+    pub const BLACK: PremultipliedColorF = PremultipliedColorF { r: 0.0, g: 0.0, b: 0.0, a: 1.0 };
+    pub const TRANSPARENT: PremultipliedColorF = PremultipliedColorF { r: 0.0, g: 0.0, b: 0.0, a: 0.0 };
+    pub const WHITE: PremultipliedColorF = PremultipliedColorF { r: 1.0, g: 1.0, b: 1.0, a: 1.0 };
+
+    pub fn to_array(&self) -> [f32; 4] {
+        [self.r, self.g, self.b, self.a]
+    }
+}
+
+/// Represents RGBA screen colors with floating point numbers.
+///
+/// All components must be between 0.0 and 1.0.
+/// An alpha value of 1.0 is opaque while 0.0 is fully transparent.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct ColorF {
+    pub r: f32,
+    pub g: f32,
+    pub b: f32,
+    pub a: f32,
+}
+
+#[allow(missing_docs)]
+impl ColorF {
+    pub const BLACK: ColorF = ColorF { r: 0.0, g: 0.0, b: 0.0, a: 1.0 };
+    pub const TRANSPARENT: ColorF = ColorF { r: 0.0, g: 0.0, b: 0.0, a: 0.0 };
+    pub const WHITE: ColorF = ColorF { r: 1.0, g: 1.0, b: 1.0, a: 1.0 };
+
+    /// Constructs a new `ColorF` from its components.
+    pub fn new(r: f32, g: f32, b: f32, a: f32) -> Self {
+        ColorF { r, g, b, a }
+    }
+
+    /// Multiply the RGB channels (but not alpha) with a given factor.
+    pub fn scale_rgb(&self, scale: f32) -> Self {
+        ColorF {
+            r: self.r * scale,
+            g: self.g * scale,
+            b: self.b * scale,
+            a: self.a,
+        }
+    }
+
+    // Scale the alpha by a given factor.
+    pub fn scale_alpha(&self, scale: f32) -> Self {
+        ColorF {
+            r: self.r,
+            g: self.g,
+            b: self.b,
+            a: self.a * scale,
+        }
+    }
+
+    pub fn to_array(&self) -> [f32; 4] {
+        [self.r, self.g, self.b, self.a]
+    }
+
+    /// Multiply the RGB components with the alpha channel.
+    pub fn premultiplied(&self) -> PremultipliedColorF {
+        let c = self.scale_rgb(self.a);
+        PremultipliedColorF { r: c.r, g: c.g, b: c.b, a: c.a }
+    }
+}
+
+// Floats don't impl Hash/Eq/Ord...
+impl Eq for PremultipliedColorF {}
+impl Ord for PremultipliedColorF {
+    fn cmp(&self, other: &Self) -> cmp::Ordering {
+        self.partial_cmp(other).unwrap_or(cmp::Ordering::Equal)
+    }
+}
+
+#[cfg_attr(feature = "cargo-clippy", allow(clippy::derive_hash_xor_eq))]
+impl Hash for PremultipliedColorF {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        // Note: this is inconsistent with the Eq impl for -0.0 (don't care).
+        self.r.to_bits().hash(state);
+        self.g.to_bits().hash(state);
+        self.b.to_bits().hash(state);
+        self.a.to_bits().hash(state);
+    }
+}
+
+/// Represents RGBA screen colors with one byte per channel.
+///
+/// If the alpha value `a` is 255 the color is opaque.
+#[repr(C)]
+#[derive(Clone, Copy, Hash, Eq, Debug, Deserialize, MallocSizeOf, PartialEq, PartialOrd, Ord, Serialize)]
+pub struct ColorU {
+    pub r: u8,
+    pub g: u8,
+    pub b: u8,
+    pub a: u8,
+}
+
+impl ColorU {
+    /// Constructs a new additive `ColorU` from its components.
+    pub fn new(r: u8, g: u8, b: u8, a: u8) -> Self {
+        ColorU { r, g, b, a }
+    }
+}
+
+fn round_to_int(x: f32) -> u8 {
+    debug_assert!((0.0 <= x) && (x <= 1.0), "{} should be between 0 and 1", x);
+    let f = (255.0 * x) + 0.5;
+    let val = f.floor();
+    debug_assert!(val <= 255.0);
+    val as u8
+}
+
+// TODO: We shouldn't really convert back to `ColorU` ever,
+// since it's lossy. One of the blockers is that all of our debug colors
+// are specified in `ColorF`. Changing it to `ColorU` would be nice.
+impl From<ColorF> for ColorU {
+    fn from(color: ColorF) -> Self {
+        ColorU {
+            r: round_to_int(color.r),
+            g: round_to_int(color.g),
+            b: round_to_int(color.b),
+            a: round_to_int(color.a),
+        }
+    }
+}
+
+impl From<ColorU> for ColorF {
+    fn from(color: ColorU) -> Self {
+        ColorF {
+            r: color.r as f32 / 255.0,
+            g: color.g as f32 / 255.0,
+            b: color.b as f32 / 255.0,
+            a: color.a as f32 / 255.0,
+        }
+    }
+}
diff --git a/gfx/wr/webrender_api/src/display_item.rs b/gfx/wr/webrender_api/src/display_item.rs
new file mode 100644
index 0000000000..1ba51f9401
--- /dev/null
+++ b/gfx/wr/webrender_api/src/display_item.rs
@@ -0,0 +1,1669 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use euclid::{SideOffsets2D, Angle};
+use peek_poke::PeekPoke;
+use std::ops::Not;
+// local imports
+use crate::font;
+use crate::{PipelineId, PropertyBinding};
+use crate::color::ColorF;
+use crate::image::{ColorDepth, ImageKey};
+use crate::units::*;
+use std::hash::{Hash, Hasher};
+
+// ******************************************************************
+// * NOTE: some of these structs have an "IMPLICIT" comment.        *
+// * This indicates that the BuiltDisplayList will have serialized  *
+// * a list of values nearby that this item consumes. The traversal *
+// * iterator should handle finding these. DebugDisplayItem should  *
+// * make them explicit.                                            *
+// ******************************************************************
+
+/// A tag that can be used to identify items during hit testing. If the tag
+/// is missing then the item doesn't take part in hit testing at all. This
+/// is composed of two numbers. In Servo, the first is an identifier while the
+/// second is used to select the cursor that should be used during mouse
+/// movement. In Gecko, the first is a scrollframe identifier, while the second
+/// is used to store various flags that APZ needs to properly process input
+/// events.
+pub type ItemTag = (u64, u16);
+
+/// An identifier used to refer to previously sent display items. Currently it
+/// refers to individual display items, but this may change later.
+pub type ItemKey = u16;
+
+bitflags! {
+    #[repr(C)]
+    #[derive(Deserialize, MallocSizeOf, Serialize, PeekPoke)]
+    pub struct PrimitiveFlags: u8 {
+        /// The CSS backface-visibility property (yes, it can be really granular)
+        const IS_BACKFACE_VISIBLE = 1 << 0;
+        /// If set, this primitive represents a scroll bar container
+        const IS_SCROLLBAR_CONTAINER = 1 << 1;
+        /// If set, this primitive represents a scroll bar thumb
+        const IS_SCROLLBAR_THUMB = 1 << 2;
+        /// This is used as a performance hint - this primitive may be promoted to a native
+        /// compositor surface under certain (implementation specific) conditions. This
+        /// is typically used for large videos, and canvas elements.
+        const PREFER_COMPOSITOR_SURFACE = 1 << 3;
+        /// If set, this primitive can be passed directly to the compositor via its
+        /// ExternalImageId, and the compositor will use the native image directly.
+        /// Used as a further extension on top of PREFER_COMPOSITOR_SURFACE.
+        const SUPPORTS_EXTERNAL_COMPOSITOR_SURFACE = 1 << 4;
+    }
+}
+
+impl Default for PrimitiveFlags {
+    fn default() -> Self {
+        PrimitiveFlags::IS_BACKFACE_VISIBLE
+    }
+}
+
+/// A grouping of fields a lot of display items need, just to avoid
+/// repeating these over and over in this file.
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct CommonItemProperties {
+    /// Bounds of the display item to clip to. Many items are logically
+    /// infinite, and rely on this clip_rect to define their bounds
+    /// (solid colors, background-images, gradients, etc).
+    pub clip_rect: LayoutRect,
+    /// Additional clips
+    pub clip_id: ClipId,
+    /// The coordinate-space the item is in (yes, it can be really granular)
+    pub spatial_id: SpatialId,
+    /// Various flags describing properties of this primitive.
+    pub flags: PrimitiveFlags,
+}
+
+impl CommonItemProperties {
+    /// Convenience for tests.
+    pub fn new(
+        clip_rect: LayoutRect,
+        space_and_clip: SpaceAndClipInfo,
+    ) -> Self {
+        Self {
+            clip_rect,
+            spatial_id: space_and_clip.spatial_id,
+            clip_id: space_and_clip.clip_id,
+            flags: PrimitiveFlags::default(),
+        }
+    }
+}
+
+/// Per-primitive information about the nodes in the clip tree and
+/// the spatial tree that the primitive belongs to.
+///
+/// Note: this is a separate struct from `PrimitiveInfo` because
+/// it needs indirectional mapping during the DL flattening phase,
+/// turning into `ScrollNodeAndClipChain`.
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct SpaceAndClipInfo {
+    pub spatial_id: SpatialId,
+    pub clip_id: ClipId,
+}
+
+impl SpaceAndClipInfo {
+    /// Create a new space/clip info associated with the root
+    /// scroll frame.
+    pub fn root_scroll(pipeline_id: PipelineId) -> Self {
+        SpaceAndClipInfo {
+            spatial_id: SpatialId::root_scroll_node(pipeline_id),
+            clip_id: ClipId::root(pipeline_id),
+        }
+    }
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum DisplayItem {
+    // These are the "real content" display items
+    Rectangle(RectangleDisplayItem),
+    ClearRectangle(ClearRectangleDisplayItem),
+    HitTest(HitTestDisplayItem),
+    Text(TextDisplayItem),
+    Line(LineDisplayItem),
+    Border(BorderDisplayItem),
+    BoxShadow(BoxShadowDisplayItem),
+    PushShadow(PushShadowDisplayItem),
+    Gradient(GradientDisplayItem),
+    RadialGradient(RadialGradientDisplayItem),
+    ConicGradient(ConicGradientDisplayItem),
+    Image(ImageDisplayItem),
+    RepeatingImage(RepeatingImageDisplayItem),
+    YuvImage(YuvImageDisplayItem),
+    BackdropFilter(BackdropFilterDisplayItem),
+
+    // Clips
+    RectClip(RectClipDisplayItem),
+    RoundedRectClip(RoundedRectClipDisplayItem),
+    ImageMaskClip(ImageMaskClipDisplayItem),
+    Clip(ClipDisplayItem),
+    ClipChain(ClipChainItem),
+
+    // Spaces and Frames that content can be scoped under.
+    ScrollFrame(ScrollFrameDisplayItem),
+    StickyFrame(StickyFrameDisplayItem),
+    Iframe(IframeDisplayItem),
+    PushReferenceFrame(ReferenceFrameDisplayListItem),
+    PushStackingContext(PushStackingContextDisplayItem),
+
+    // These marker items indicate an array of data follows, to be used for the
+    // next non-marker item.
+    SetGradientStops,
+    SetFilterOps,
+    SetFilterData,
+    SetFilterPrimitives,
+
+    // These marker items terminate a scope introduced by a previous item.
+    PopReferenceFrame,
+    PopStackingContext,
+    PopAllShadows,
+
+    ReuseItems(ItemKey),
+    RetainedItems(ItemKey),
+}
+
+/// This is a "complete" version of the DisplayItem, with all implicit trailing
+/// arrays included, for debug serialization (captures).
+#[cfg(any(feature = "serialize", feature = "deserialize"))]
+#[cfg_attr(feature = "serialize", derive(Serialize))]
+#[cfg_attr(feature = "deserialize", derive(Deserialize))]
+pub enum DebugDisplayItem {
+    Rectangle(RectangleDisplayItem),
+    ClearRectangle(ClearRectangleDisplayItem),
+    HitTest(HitTestDisplayItem),
+    Text(TextDisplayItem, Vec<font::GlyphInstance>),
+    Line(LineDisplayItem),
+    Border(BorderDisplayItem),
+    BoxShadow(BoxShadowDisplayItem),
+    PushShadow(PushShadowDisplayItem),
+    Gradient(GradientDisplayItem),
+    RadialGradient(RadialGradientDisplayItem),
+    ConicGradient(ConicGradientDisplayItem),
+    Image(ImageDisplayItem),
+    RepeatingImage(RepeatingImageDisplayItem),
+    YuvImage(YuvImageDisplayItem),
+    BackdropFilter(BackdropFilterDisplayItem),
+
+    ImageMaskClip(ImageMaskClipDisplayItem),
+    RoundedRectClip(RoundedRectClipDisplayItem),
+    RectClip(RectClipDisplayItem),
+    Clip(ClipDisplayItem, Vec<ComplexClipRegion>),
+    ClipChain(ClipChainItem, Vec<ClipId>),
+
+    ScrollFrame(ScrollFrameDisplayItem),
+    StickyFrame(StickyFrameDisplayItem),
+    Iframe(IframeDisplayItem),
+    PushReferenceFrame(ReferenceFrameDisplayListItem),
+    PushStackingContext(PushStackingContextDisplayItem),
+
+    SetGradientStops(Vec<GradientStop>),
+    SetFilterOps(Vec<FilterOp>),
+    SetFilterData(FilterData),
+    SetFilterPrimitives(Vec<FilterPrimitive>),
+
+    PopReferenceFrame,
+    PopStackingContext,
+    PopAllShadows,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ImageMaskClipDisplayItem {
+    pub id: ClipId,
+    pub parent_space_and_clip: SpaceAndClipInfo,
+    pub image_mask: ImageMask,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct RectClipDisplayItem {
+    pub id: ClipId,
+    pub parent_space_and_clip: SpaceAndClipInfo,
+    pub clip_rect: LayoutRect,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct RoundedRectClipDisplayItem {
+    pub id: ClipId,
+    pub parent_space_and_clip: SpaceAndClipInfo,
+    pub clip: ComplexClipRegion,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ClipDisplayItem {
+    pub id: ClipId,
+    pub parent_space_and_clip: SpaceAndClipInfo,
+    pub clip_rect: LayoutRect,
+} // IMPLICIT: complex_clips: Vec<ComplexClipRegion>
+
+/// The minimum and maximum allowable offset for a sticky frame in a single dimension.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct StickyOffsetBounds {
+    /// The minimum offset for this frame, typically a negative value, which specifies how
+    /// far in the negative direction the sticky frame can offset its contents in this
+    /// dimension.
+    pub min: f32,
+
+    /// The maximum offset for this frame, typically a positive value, which specifies how
+    /// far in the positive direction the sticky frame can offset its contents in this
+    /// dimension.
+    pub max: f32,
+}
+
+impl StickyOffsetBounds {
+    pub fn new(min: f32, max: f32) -> StickyOffsetBounds {
+        StickyOffsetBounds { min, max }
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct StickyFrameDisplayItem {
+    pub id: SpatialId,
+    pub parent_spatial_id: SpatialId,
+    pub bounds: LayoutRect,
+
+    /// The margins that should be maintained between the edge of the parent viewport and this
+    /// sticky frame. A margin of None indicates that the sticky frame should not stick at all
+    /// to that particular edge of the viewport.
+    pub margins: SideOffsets2D<Option<f32>, LayoutPixel>,
+
+    /// The minimum and maximum vertical offsets for this sticky frame. Ignoring these constraints,
+    /// the sticky frame will continue to stick to the edge of the viewport as its original
+    /// position is scrolled out of view. Constraints specify a maximum and minimum offset from the
+    /// original position relative to non-sticky content within the same scrolling frame.
+    pub vertical_offset_bounds: StickyOffsetBounds,
+
+    /// The minimum and maximum horizontal offsets for this sticky frame. Ignoring these constraints,
+    /// the sticky frame will continue to stick to the edge of the viewport as its original
+    /// position is scrolled out of view. Constraints specify a maximum and minimum offset from the
+    /// original position relative to non-sticky content within the same scrolling frame.
+    pub horizontal_offset_bounds: StickyOffsetBounds,
+
+    /// The amount of offset that has already been applied to the sticky frame. A positive y
+    /// component this field means that a top-sticky item was in a scrollframe that has been
+    /// scrolled down, such that the sticky item's position needed to be offset downwards by
+    /// `previously_applied_offset.y`. A negative y component corresponds to the upward offset
+    /// applied due to bottom-stickiness. The x-axis works analogously.
+    pub previously_applied_offset: LayoutVector2D,
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum ScrollSensitivity {
+    ScriptAndInputEvents,
+    Script,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ScrollFrameDisplayItem {
+    /// The id of the clip this scroll frame creates
+    pub clip_id: ClipId,
+    /// The id of the space this scroll frame creates
+    pub scroll_frame_id: SpatialId,
+    /// The size of the contents this contains (so the backend knows how far it can scroll).
+    // FIXME: this can *probably* just be a size? Origin seems to just get thrown out.
+    pub content_rect: LayoutRect,
+    pub clip_rect: LayoutRect,
+    pub parent_space_and_clip: SpaceAndClipInfo,
+    pub external_id: ExternalScrollId,
+    pub scroll_sensitivity: ScrollSensitivity,
+    /// The amount this scrollframe has already been scrolled by, in the caller.
+    /// This means that all the display items that are inside the scrollframe
+    /// will have their coordinates shifted by this amount, and this offset
+    /// should be added to those display item coordinates in order to get a
+    /// normalized value that is consistent across display lists.
+    pub external_scroll_offset: LayoutVector2D,
+}
+
+/// A solid or an animating color to draw (may not actually be a rectangle due to complex clips)
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct RectangleDisplayItem {
+    pub common: CommonItemProperties,
+    pub bounds: LayoutRect,
+    pub color: PropertyBinding<ColorF>,
+}
+
+/// Clears all colors from the area, making it possible to cut holes in the window.
+/// (useful for things like the macos frosted-glass effect).
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ClearRectangleDisplayItem {
+    pub common: CommonItemProperties,
+    pub bounds: LayoutRect,
+}
+
+/// A minimal hit-testable item for the parent browser's convenience, and is
+/// slimmer than a RectangleDisplayItem (no color). The existence of this as a
+/// distinct item also makes it easier to inspect/debug display items.
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct HitTestDisplayItem {
+    pub common: CommonItemProperties,
+    pub tag: ItemTag,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct LineDisplayItem {
+    pub common: CommonItemProperties,
+    /// We need a separate rect from common.clip_rect to encode cute
+    /// tricks that firefox does to make a series of text-decorations seamlessly
+    /// line up -- snapping the decorations to a multiple of their period, and
+    /// then clipping them to their "proper" area. This rect is that "logical"
+    /// snapped area that may be clipped to the right size by the clip_rect.
+    pub area: LayoutRect,
+    /// Whether the rect is interpretted as vertical or horizontal
+    pub orientation: LineOrientation,
+    /// This could potentially be implied from area, but we currently prefer
+    /// that this is the responsibility of the layout engine. Value irrelevant
+    /// for non-wavy lines.
+    // FIXME: this was done before we could use tagged unions in enums, but now
+    // it should just be part of LineStyle::Wavy.
+    pub wavy_line_thickness: f32,
+    pub color: ColorF,
+    pub style: LineStyle,
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize, Eq, Hash, PeekPoke)]
+pub enum LineOrientation {
+    Vertical,
+    Horizontal,
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize, Eq, Hash, PeekPoke)]
+pub enum LineStyle {
+    Solid,
+    Dotted,
+    Dashed,
+    Wavy,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct TextDisplayItem {
+    pub common: CommonItemProperties,
+    /// The area all the glyphs should be found in. Strictly speaking this isn't
+    /// necessarily needed, but layout engines should already "know" this, and we
+    /// use it cull and size things quickly before glyph layout is done. Currently
+    /// the glyphs *can* be outside these bounds, but that should imply they
+    /// can be cut off.
+    // FIXME: these are currently sometimes ignored to keep some old wrench tests
+    // working, but we should really just fix the tests!
+    pub bounds: LayoutRect,
+    pub font_key: font::FontInstanceKey,
+    pub color: ColorF,
+    pub glyph_options: Option<font::GlyphOptions>,
+} // IMPLICIT: glyphs: Vec<font::GlyphInstance>
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct NormalBorder {
+    pub left: BorderSide,
+    pub right: BorderSide,
+    pub top: BorderSide,
+    pub bottom: BorderSide,
+    pub radius: BorderRadius,
+    /// Whether to apply anti-aliasing on the border corners.
+    ///
+    /// Note that for this to be `false` and work, this requires the borders to
+    /// be solid, and no border-radius.
+    pub do_aa: bool,
+}
+
+impl NormalBorder {
+    fn can_disable_antialiasing(&self) -> bool {
+        fn is_valid(style: BorderStyle) -> bool {
+            style == BorderStyle::Solid || style == BorderStyle::None
+        }
+
+        self.radius.is_zero() &&
+            is_valid(self.top.style) &&
+            is_valid(self.left.style) &&
+            is_valid(self.bottom.style) &&
+            is_valid(self.right.style)
+    }
+
+    /// Normalizes a border so that we don't render disallowed stuff, like inset
+    /// borders that are less than two pixels wide.
+    #[inline]
+    pub fn normalize(&mut self, widths: &LayoutSideOffsets) {
+        debug_assert!(
+            self.do_aa || self.can_disable_antialiasing(),
+            "Unexpected disabled-antialiasing in a border, likely won't work or will be ignored"
+        );
+
+        #[inline]
+        fn renders_small_border_solid(style: BorderStyle) -> bool {
+            match style {
+                BorderStyle::Groove |
+                BorderStyle::Ridge => true,
+                _ => false,
+            }
+        }
+
+        let normalize_side = |side: &mut BorderSide, width: f32| {
+            if renders_small_border_solid(side.style) && width < 2. {
+                side.style = BorderStyle::Solid;
+            }
+        };
+
+        normalize_side(&mut self.left, widths.left);
+        normalize_side(&mut self.right, widths.right);
+        normalize_side(&mut self.top, widths.top);
+        normalize_side(&mut self.bottom, widths.bottom);
+    }
+}
+
+#[repr(u8)]
+#[derive(Debug, Copy, Clone, MallocSizeOf, PartialEq, Serialize, Deserialize, Eq, Hash, PeekPoke)]
+pub enum RepeatMode {
+    Stretch,
+    Repeat,
+    Round,
+    Space,
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum NinePatchBorderSource {
+    Image(ImageKey),
+    Gradient(Gradient),
+    RadialGradient(RadialGradient),
+    ConicGradient(ConicGradient),
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct NinePatchBorder {
+    /// Describes what to use as the 9-patch source image. If this is an image,
+    /// it will be stretched to fill the size given by width x height.
+    pub source: NinePatchBorderSource,
+
+    /// The width of the 9-part image.
+    pub width: i32,
+
+    /// The height of the 9-part image.
+    pub height: i32,
+
+    /// Distances from each edge where the image should be sliced up. These
+    /// values are in 9-part-image space (the same space as width and height),
+    /// and the resulting image parts will be used to fill the corresponding
+    /// parts of the border as given by the border widths. This can lead to
+    /// stretching.
+    /// Slices can be overlapping. In that case, the same pixels from the
+    /// 9-part image will show up in multiple parts of the resulting border.
+    pub slice: DeviceIntSideOffsets,
+
+    /// Controls whether the center of the 9 patch image is rendered or
+    /// ignored. The center is never rendered if the slices are overlapping.
+    pub fill: bool,
+
+    /// Determines what happens if the horizontal side parts of the 9-part
+    /// image have a different size than the horizontal parts of the border.
+    pub repeat_horizontal: RepeatMode,
+
+    /// Determines what happens if the vertical side parts of the 9-part
+    /// image have a different size than the vertical parts of the border.
+    pub repeat_vertical: RepeatMode,
+
+    /// The outset for the border.
+    /// TODO(mrobinson): This should be removed and handled by the client.
+    pub outset: LayoutSideOffsets, // TODO: what unit is this in?
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum BorderDetails {
+    Normal(NormalBorder),
+    NinePatch(NinePatchBorder),
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct BorderDisplayItem {
+    pub common: CommonItemProperties,
+    pub bounds: LayoutRect,
+    pub widths: LayoutSideOffsets,
+    pub details: BorderDetails,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum BorderRadiusKind {
+    Uniform,
+    NonUniform,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct BorderRadius {
+    pub top_left: LayoutSize,
+    pub top_right: LayoutSize,
+    pub bottom_left: LayoutSize,
+    pub bottom_right: LayoutSize,
+}
+
+impl Default for BorderRadius {
+    fn default() -> Self {
+        BorderRadius {
+            top_left: LayoutSize::zero(),
+            top_right: LayoutSize::zero(),
+            bottom_left: LayoutSize::zero(),
+            bottom_right: LayoutSize::zero(),
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct BorderSide {
+    pub color: ColorF,
+    pub style: BorderStyle,
+}
+
+#[repr(u32)]
+#[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize, Hash, Eq, PeekPoke)]
+pub enum BorderStyle {
+    None = 0,
+    Solid = 1,
+    Double = 2,
+    Dotted = 3,
+    Dashed = 4,
+    Hidden = 5,
+    Groove = 6,
+    Ridge = 7,
+    Inset = 8,
+    Outset = 9,
+}
+
+impl BorderStyle {
+    pub fn is_hidden(self) -> bool {
+        self == BorderStyle::Hidden || self == BorderStyle::None
+    }
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum BoxShadowClipMode {
+    Outset = 0,
+    Inset = 1,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct BoxShadowDisplayItem {
+    pub common: CommonItemProperties,
+    pub box_bounds: LayoutRect,
+    pub offset: LayoutVector2D,
+    pub color: ColorF,
+    pub blur_radius: f32,
+    pub spread_radius: f32,
+    pub border_radius: BorderRadius,
+    pub clip_mode: BoxShadowClipMode,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct PushShadowDisplayItem {
+    pub space_and_clip: SpaceAndClipInfo,
+    pub shadow: Shadow,
+    pub should_inflate: bool,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct Shadow {
+    pub offset: LayoutVector2D,
+    pub color: ColorF,
+    pub blur_radius: f32,
+}
+
+#[repr(u8)]
+#[derive(Debug, Copy, Clone, Hash, Eq, MallocSizeOf, PartialEq, Serialize, Deserialize, Ord, PartialOrd, PeekPoke)]
+pub enum ExtendMode {
+    Clamp,
+    Repeat,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct Gradient {
+    pub start_point: LayoutPoint,
+    pub end_point: LayoutPoint,
+    pub extend_mode: ExtendMode,
+} // IMPLICIT: stops: Vec<GradientStop>
+
+/// The area
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct GradientDisplayItem {
+    /// NOTE: common.clip_rect is the area the gradient covers
+    pub common: CommonItemProperties,
+    /// The area to tile the gradient over (first tile starts at origin of this rect)
+    // FIXME: this should ideally just be `tile_origin` here, with the clip_rect
+    // defining the bounds of the item. Needs non-trivial backend changes.
+    pub bounds: LayoutRect,
+    /// How big a tile of the of the gradient should be (common case: bounds.size)
+    pub tile_size: LayoutSize,
+    /// The space between tiles of the gradient (common case: 0)
+    pub tile_spacing: LayoutSize,
+    pub gradient: Gradient,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct GradientStop {
+    pub offset: f32,
+    pub color: ColorF,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct RadialGradient {
+    pub center: LayoutPoint,
+    pub radius: LayoutSize,
+    pub start_offset: f32,
+    pub end_offset: f32,
+    pub extend_mode: ExtendMode,
+} // IMPLICIT stops: Vec<GradientStop>
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ConicGradient {
+    pub center: LayoutPoint,
+    pub angle: f32,
+    pub start_offset: f32,
+    pub end_offset: f32,
+    pub extend_mode: ExtendMode,
+} // IMPLICIT stops: Vec<GradientStop>
+
+/// Just an abstraction for bundling up a bunch of clips into a "super clip".
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ClipChainItem {
+    pub id: ClipChainId,
+    pub parent: Option<ClipChainId>,
+} // IMPLICIT clip_ids: Vec<ClipId>
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct RadialGradientDisplayItem {
+    pub common: CommonItemProperties,
+    /// The area to tile the gradient over (first tile starts at origin of this rect)
+    // FIXME: this should ideally just be `tile_origin` here, with the clip_rect
+    // defining the bounds of the item. Needs non-trivial backend changes.
+    pub bounds: LayoutRect,
+    pub gradient: RadialGradient,
+    pub tile_size: LayoutSize,
+    pub tile_spacing: LayoutSize,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ConicGradientDisplayItem {
+    pub common: CommonItemProperties,
+    /// The area to tile the gradient over (first tile starts at origin of this rect)
+    // FIXME: this should ideally just be `tile_origin` here, with the clip_rect
+    // defining the bounds of the item. Needs non-trivial backend changes.
+    pub bounds: LayoutRect,
+    pub gradient: ConicGradient,
+    pub tile_size: LayoutSize,
+    pub tile_spacing: LayoutSize,
+}
+
+/// Renders a filtered region of its backdrop
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct BackdropFilterDisplayItem {
+    pub common: CommonItemProperties,
+}
+// IMPLICIT: filters: Vec<FilterOp>, filter_datas: Vec<FilterData>, filter_primitives: Vec<FilterPrimitive>
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ReferenceFrameDisplayListItem {
+    pub origin: LayoutPoint,
+    pub parent_spatial_id: SpatialId,
+    pub reference_frame: ReferenceFrame,
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum ReferenceFrameKind {
+    /// Zoom reference frames must be a scale + translation only
+    Zoom,
+    /// A normal transform matrix, may contain perspective (the CSS transform property)
+    Transform,
+    /// A perspective transform, that optionally scrolls relative to a specific scroll node
+    Perspective {
+        scrolling_relative_to: Option<ExternalScrollId>,
+    }
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum Rotation {
+    Degree0,
+    Degree90,
+    Degree180,
+    Degree270,
+}
+
+impl Rotation {
+    pub fn to_matrix(
+        &self,
+        size: LayoutSize,
+    ) -> LayoutTransform {
+        let (shift_center_to_origin, angle) = match self {
+            Rotation::Degree0 => {
+              (LayoutTransform::translation(-size.width / 2., -size.height / 2., 0.), Angle::degrees(0.))
+            },
+            Rotation::Degree90 => {
+              (LayoutTransform::translation(-size.height / 2., -size.width / 2., 0.), Angle::degrees(90.))
+            },
+            Rotation::Degree180 => {
+              (LayoutTransform::translation(-size.width / 2., -size.height / 2., 0.), Angle::degrees(180.))
+            },
+            Rotation::Degree270 => {
+              (LayoutTransform::translation(-size.height / 2., -size.width / 2., 0.), Angle::degrees(270.))
+            },
+        };
+        let shift_origin_to_center = LayoutTransform::translation(size.width / 2., size.height / 2., 0.);
+
+        shift_center_to_origin
+            .then(&LayoutTransform::rotation(0., 0., 1.0, angle))
+            .then(&shift_origin_to_center)
+    }
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum ReferenceTransformBinding {
+    /// Standard reference frame which contains a precomputed transform.
+    Static {
+        binding: PropertyBinding<LayoutTransform>,
+    },
+    /// Computed reference frame which dynamically calculates the transform
+    /// based on the given parameters. The reference is the content size of
+    /// the parent iframe, which is affected by snapping.
+    Computed {
+        scale_from: Option<LayoutSize>,
+        vertical_flip: bool,
+        rotation: Rotation,
+    },
+}
+
+impl Default for ReferenceTransformBinding {
+    fn default() -> Self {
+        ReferenceTransformBinding::Static {
+            binding: Default::default(),
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ReferenceFrame {
+    pub kind: ReferenceFrameKind,
+    pub transform_style: TransformStyle,
+    /// The transform matrix, either the perspective matrix or the transform
+    /// matrix.
+    pub transform: ReferenceTransformBinding,
+    pub id: SpatialId,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct PushStackingContextDisplayItem {
+    pub origin: LayoutPoint,
+    pub spatial_id: SpatialId,
+    pub prim_flags: PrimitiveFlags,
+    pub stacking_context: StackingContext,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct StackingContext {
+    pub transform_style: TransformStyle,
+    pub mix_blend_mode: MixBlendMode,
+    pub clip_id: Option<ClipId>,
+    pub raster_space: RasterSpace,
+    pub flags: StackingContextFlags,
+}
+// IMPLICIT: filters: Vec<FilterOp>, filter_datas: Vec<FilterData>, filter_primitives: Vec<FilterPrimitive>
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, PartialEq, Serialize, PeekPoke)]
+pub enum TransformStyle {
+    Flat = 0,
+    Preserve3D = 1,
+}
+
+/// Configure whether the contents of a stacking context
+/// should be rasterized in local space or screen space.
+/// Local space rasterized pictures are typically used
+/// when we want to cache the output, and performance is
+/// important. Note that this is a performance hint only,
+/// which WR may choose to ignore.
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, MallocSizeOf, Serialize, PeekPoke)]
+#[repr(u8)]
+pub enum RasterSpace {
+    // Rasterize in local-space, applying supplied scale to primitives.
+    // Best performance, but lower quality.
+    Local(f32),
+
+    // Rasterize the picture in screen-space, including rotation / skew etc in
+    // the rasterized element. Best quality, but slower performance. Note that
+    // any stacking context with a perspective transform will be rasterized
+    // in local-space, even if this is set.
+    Screen,
+}
+
+impl RasterSpace {
+    pub fn local_scale(self) -> Option<f32> {
+        match self {
+            RasterSpace::Local(scale) => Some(scale),
+            RasterSpace::Screen => None,
+        }
+    }
+}
+
+impl Eq for RasterSpace {}
+
+impl Hash for RasterSpace {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        match self {
+            RasterSpace::Screen => {
+                0.hash(state);
+            }
+            RasterSpace::Local(scale) => {
+                // Note: this is inconsistent with the Eq impl for -0.0 (don't care).
+                1.hash(state);
+                scale.to_bits().hash(state);
+            }
+        }
+    }
+}
+
+bitflags! {
+    #[repr(C)]
+    #[derive(Deserialize, MallocSizeOf, Serialize, PeekPoke)]
+    pub struct StackingContextFlags: u8 {
+        /// If true, this stacking context represents a backdrop root, per the CSS
+        /// filter-effects specification (see https://drafts.fxtf.org/filter-effects-2/#BackdropRoot).
+        const IS_BACKDROP_ROOT = 1 << 0;
+        /// If true, this stacking context is a blend container than contains
+        /// mix-blend-mode children (and should thus be isolated).
+        const IS_BLEND_CONTAINER = 1 << 1;
+    }
+}
+
+impl Default for StackingContextFlags {
+    fn default() -> Self {
+        StackingContextFlags::empty()
+    }
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum MixBlendMode {
+    Normal = 0,
+    Multiply = 1,
+    Screen = 2,
+    Overlay = 3,
+    Darken = 4,
+    Lighten = 5,
+    ColorDodge = 6,
+    ColorBurn = 7,
+    HardLight = 8,
+    SoftLight = 9,
+    Difference = 10,
+    Exclusion = 11,
+    Hue = 12,
+    Saturation = 13,
+    Color = 14,
+    Luminosity = 15,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum ColorSpace {
+    Srgb,
+    LinearRgb,
+}
+
+/// Available composite operoations for the composite filter primitive
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum CompositeOperator {
+    Over,
+    In,
+    Atop,
+    Out,
+    Xor,
+    Lighter,
+    Arithmetic([f32; 4]),
+}
+
+impl CompositeOperator {
+    // This must stay in sync with the composite operator defines in cs_svg_filter.glsl
+    pub fn as_int(&self) -> u32 {
+        match self {
+            CompositeOperator::Over => 0,
+            CompositeOperator::In => 1,
+            CompositeOperator::Out => 2,
+            CompositeOperator::Atop => 3,
+            CompositeOperator::Xor => 4,
+            CompositeOperator::Lighter => 5,
+            CompositeOperator::Arithmetic(..) => 6,
+        }
+    }
+}
+
+/// An input to a SVG filter primitive.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum FilterPrimitiveInput {
+    /// The input is the original graphic that the filter is being applied to.
+    Original,
+    /// The input is the output of the previous filter primitive in the filter primitive chain.
+    Previous,
+    /// The input is the output of the filter primitive at the given index in the filter primitive chain.
+    OutputOfPrimitiveIndex(usize),
+}
+
+impl FilterPrimitiveInput {
+    /// Gets the index of the input.
+    /// Returns `None` if the source graphic is the input.
+    pub fn to_index(self, cur_index: usize) -> Option<usize> {
+        match self {
+            FilterPrimitiveInput::Previous if cur_index > 0 => Some(cur_index - 1),
+            FilterPrimitiveInput::OutputOfPrimitiveIndex(index) => Some(index),
+            _ => None,
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct BlendPrimitive {
+    pub input1: FilterPrimitiveInput,
+    pub input2: FilterPrimitiveInput,
+    pub mode: MixBlendMode,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct FloodPrimitive {
+    pub color: ColorF,
+}
+
+impl FloodPrimitive {
+    pub fn sanitize(&mut self) {
+        self.color.r = self.color.r.min(1.0).max(0.0);
+        self.color.g = self.color.g.min(1.0).max(0.0);
+        self.color.b = self.color.b.min(1.0).max(0.0);
+        self.color.a = self.color.a.min(1.0).max(0.0);
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct BlurPrimitive {
+    pub input: FilterPrimitiveInput,
+    pub width: f32,
+    pub height: f32,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct OpacityPrimitive {
+    pub input: FilterPrimitiveInput,
+    pub opacity: f32,
+}
+
+impl OpacityPrimitive {
+    pub fn sanitize(&mut self) {
+        self.opacity = self.opacity.min(1.0).max(0.0);
+    }
+}
+
+/// cbindgen:derive-eq=false
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ColorMatrixPrimitive {
+    pub input: FilterPrimitiveInput,
+    pub matrix: [f32; 20],
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct DropShadowPrimitive {
+    pub input: FilterPrimitiveInput,
+    pub shadow: Shadow,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ComponentTransferPrimitive {
+    pub input: FilterPrimitiveInput,
+    // Component transfer data is stored in FilterData.
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct IdentityPrimitive {
+    pub input: FilterPrimitiveInput,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct OffsetPrimitive {
+    pub input: FilterPrimitiveInput,
+    pub offset: LayoutVector2D,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct CompositePrimitive {
+    pub input1: FilterPrimitiveInput,
+    pub input2: FilterPrimitiveInput,
+    pub operator: CompositeOperator,
+}
+
+/// See: https://github.com/eqrion/cbindgen/issues/9
+/// cbindgen:derive-eq=false
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub enum FilterPrimitiveKind {
+    Identity(IdentityPrimitive),
+    Blend(BlendPrimitive),
+    Flood(FloodPrimitive),
+    Blur(BlurPrimitive),
+    // TODO: Support animated opacity?
+    Opacity(OpacityPrimitive),
+    /// cbindgen:derive-eq=false
+    ColorMatrix(ColorMatrixPrimitive),
+    DropShadow(DropShadowPrimitive),
+    ComponentTransfer(ComponentTransferPrimitive),
+    Offset(OffsetPrimitive),
+    Composite(CompositePrimitive),
+}
+
+impl Default for FilterPrimitiveKind {
+    fn default() -> Self {
+        FilterPrimitiveKind::Identity(IdentityPrimitive::default())
+    }
+}
+
+impl FilterPrimitiveKind {
+    pub fn sanitize(&mut self) {
+        match self {
+            FilterPrimitiveKind::Flood(flood) => flood.sanitize(),
+            FilterPrimitiveKind::Opacity(opacity) => opacity.sanitize(),
+
+            // No sanitization needed.
+            FilterPrimitiveKind::Identity(..) |
+            FilterPrimitiveKind::Blend(..) |
+            FilterPrimitiveKind::ColorMatrix(..) |
+            FilterPrimitiveKind::Offset(..) |
+            FilterPrimitiveKind::Composite(..) |
+            FilterPrimitiveKind::Blur(..) |
+            FilterPrimitiveKind::DropShadow(..) |
+            // Component transfer's filter data is sanitized separately.
+            FilterPrimitiveKind::ComponentTransfer(..) => {}
+        }
+    }
+}
+
+/// SVG Filter Primitive.
+/// See: https://github.com/eqrion/cbindgen/issues/9
+/// cbindgen:derive-eq=false
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct FilterPrimitive {
+    pub kind: FilterPrimitiveKind,
+    pub color_space: ColorSpace,
+}
+
+impl FilterPrimitive {
+    pub fn sanitize(&mut self) {
+        self.kind.sanitize();
+    }
+}
+
+/// CSS filter.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, PartialEq, Deserialize, Serialize, PeekPoke)]
+pub enum FilterOp {
+    /// Filter that does no transformation of the colors, needed for
+    /// debug purposes only.
+    Identity,
+    Blur(f32, f32),
+    Brightness(f32),
+    Contrast(f32),
+    Grayscale(f32),
+    HueRotate(f32),
+    Invert(f32),
+    Opacity(PropertyBinding<f32>, f32),
+    Saturate(f32),
+    Sepia(f32),
+    DropShadow(Shadow),
+    ColorMatrix([f32; 20]),
+    SrgbToLinear,
+    LinearToSrgb,
+    ComponentTransfer,
+    Flood(ColorF),
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, PartialEq, Deserialize, Serialize, PeekPoke)]
+pub enum ComponentTransferFuncType {
+  Identity = 0,
+  Table = 1,
+  Discrete = 2,
+  Linear = 3,
+  Gamma = 4,
+}
+
+#[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
+pub struct FilterData {
+    pub func_r_type: ComponentTransferFuncType,
+    pub r_values: Vec<f32>,
+    pub func_g_type: ComponentTransferFuncType,
+    pub g_values: Vec<f32>,
+    pub func_b_type: ComponentTransferFuncType,
+    pub b_values: Vec<f32>,
+    pub func_a_type: ComponentTransferFuncType,
+    pub a_values: Vec<f32>,
+}
+
+fn sanitize_func_type(
+    func_type: ComponentTransferFuncType,
+    values: &[f32],
+) -> ComponentTransferFuncType {
+    if values.is_empty() {
+        return ComponentTransferFuncType::Identity;
+    }
+    if values.len() < 2 && func_type == ComponentTransferFuncType::Linear {
+        return ComponentTransferFuncType::Identity;
+    }
+    if values.len() < 3 && func_type == ComponentTransferFuncType::Gamma {
+        return ComponentTransferFuncType::Identity;
+    }
+    func_type
+}
+
+fn sanitize_values(
+    func_type: ComponentTransferFuncType,
+    values: &[f32],
+) -> bool {
+    if values.len() < 2 && func_type == ComponentTransferFuncType::Linear {
+        return false;
+    }
+    if values.len() < 3 && func_type == ComponentTransferFuncType::Gamma {
+        return false;
+    }
+    true
+}
+
+impl FilterData {
+    /// Ensure that the number of values matches up with the function type.
+    pub fn sanitize(&self) -> FilterData {
+        FilterData {
+            func_r_type: sanitize_func_type(self.func_r_type, &self.r_values),
+            r_values:
+                    if sanitize_values(self.func_r_type, &self.r_values) {
+                        self.r_values.clone()
+                    } else {
+                        Vec::new()
+                    },
+            func_g_type: sanitize_func_type(self.func_g_type, &self.g_values),
+            g_values:
+                    if sanitize_values(self.func_g_type, &self.g_values) {
+                        self.g_values.clone()
+                    } else {
+                        Vec::new()
+                    },
+
+            func_b_type: sanitize_func_type(self.func_b_type, &self.b_values),
+            b_values:
+                    if sanitize_values(self.func_b_type, &self.b_values) {
+                        self.b_values.clone()
+                    } else {
+                        Vec::new()
+                    },
+
+            func_a_type: sanitize_func_type(self.func_a_type, &self.a_values),
+            a_values:
+                    if sanitize_values(self.func_a_type, &self.a_values) {
+                        self.a_values.clone()
+                    } else {
+                        Vec::new()
+                    },
+
+        }
+    }
+
+    pub fn is_identity(&self) -> bool {
+        self.func_r_type == ComponentTransferFuncType::Identity &&
+        self.func_g_type == ComponentTransferFuncType::Identity &&
+        self.func_b_type == ComponentTransferFuncType::Identity &&
+        self.func_a_type == ComponentTransferFuncType::Identity
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct IframeDisplayItem {
+    pub bounds: LayoutRect,
+    pub clip_rect: LayoutRect,
+    pub space_and_clip: SpaceAndClipInfo,
+    pub pipeline_id: PipelineId,
+    pub ignore_missing_pipeline: bool,
+}
+
+/// This describes an image that fills the specified area. It stretches or shrinks
+/// the image as necessary. While RepeatingImageDisplayItem could otherwise provide
+/// a superset of the functionality, it has been problematic inferring the desired
+/// repetition properties when snapping changes the size of the primitive.
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ImageDisplayItem {
+    pub common: CommonItemProperties,
+    /// The area to tile the image over (first tile starts at origin of this rect)
+    // FIXME: this should ideally just be `tile_origin` here, with the clip_rect
+    // defining the bounds of the item. Needs non-trivial backend changes.
+    pub bounds: LayoutRect,
+    pub image_key: ImageKey,
+    pub image_rendering: ImageRendering,
+    pub alpha_type: AlphaType,
+    /// A hack used by gecko to color a simple bitmap font used for tofu glyphs
+    pub color: ColorF,
+}
+
+/// This describes a background-image and its tiling. It repeats in a grid to fill
+/// the specified area.
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct RepeatingImageDisplayItem {
+    pub common: CommonItemProperties,
+    /// The area to tile the image over (first tile starts at origin of this rect)
+    // FIXME: this should ideally just be `tile_origin` here, with the clip_rect
+    // defining the bounds of the item. Needs non-trivial backend changes.
+    pub bounds: LayoutRect,
+    /// How large to make a single tile of the image (common case: bounds.size)
+    pub stretch_size: LayoutSize,
+    /// The space between tiles (common case: 0)
+    pub tile_spacing: LayoutSize,
+    pub image_key: ImageKey,
+    pub image_rendering: ImageRendering,
+    pub alpha_type: AlphaType,
+    /// A hack used by gecko to color a simple bitmap font used for tofu glyphs
+    pub color: ColorF,
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum ImageRendering {
+    Auto = 0,
+    CrispEdges = 1,
+    Pixelated = 2,
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum AlphaType {
+    Alpha = 0,
+    PremultipliedAlpha = 1,
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct YuvImageDisplayItem {
+    pub common: CommonItemProperties,
+    pub bounds: LayoutRect,
+    pub yuv_data: YuvData,
+    pub color_depth: ColorDepth,
+    pub color_space: YuvColorSpace,
+    pub color_range: ColorRange,
+    pub image_rendering: ImageRendering,
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum YuvColorSpace {
+    Rec601 = 0,
+    Rec709 = 1,
+    Rec2020 = 2,
+    Identity = 3, // aka RGB as per ISO/IEC 23091-2:2019
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum ColorRange {
+    Limited = 0,
+    Full = 1,
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, PartialEq, Serialize, PeekPoke)]
+pub enum YuvData {
+    NV12(ImageKey, ImageKey), // (Y channel, CbCr interleaved channel)
+    PlanarYCbCr(ImageKey, ImageKey, ImageKey), // (Y channel, Cb channel, Cr Channel)
+    InterleavedYCbCr(ImageKey), // (YCbCr interleaved channel)
+}
+
+impl YuvData {
+    pub fn get_format(&self) -> YuvFormat {
+        match *self {
+            YuvData::NV12(..) => YuvFormat::NV12,
+            YuvData::PlanarYCbCr(..) => YuvFormat::PlanarYCbCr,
+            YuvData::InterleavedYCbCr(..) => YuvFormat::InterleavedYCbCr,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum YuvFormat {
+    NV12 = 0,
+    PlanarYCbCr = 1,
+    InterleavedYCbCr = 2,
+}
+
+impl YuvFormat {
+    pub fn get_plane_num(self) -> usize {
+        match self {
+            YuvFormat::NV12 => 2,
+            YuvFormat::PlanarYCbCr => 3,
+            YuvFormat::InterleavedYCbCr => 1,
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ImageMask {
+    pub image: ImageKey,
+    pub rect: LayoutRect,
+    pub repeat: bool,
+}
+
+impl ImageMask {
+    /// Get a local clipping rect contributed by this mask.
+    pub fn get_local_clip_rect(&self) -> Option<LayoutRect> {
+        if self.repeat {
+            None
+        } else {
+            Some(self.rect)
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Copy, Clone, Debug, MallocSizeOf, PartialEq, Serialize, Deserialize, Eq, Hash, PeekPoke)]
+pub enum ClipMode {
+    Clip,    // Pixels inside the region are visible.
+    ClipOut, // Pixels outside the region are visible.
+}
+
+impl Not for ClipMode {
+    type Output = ClipMode;
+
+    fn not(self) -> ClipMode {
+        match self {
+            ClipMode::Clip => ClipMode::ClipOut,
+            ClipMode::ClipOut => ClipMode::Clip,
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, PartialEq, Serialize, PeekPoke)]
+pub struct ComplexClipRegion {
+    /// The boundaries of the rectangle.
+    pub rect: LayoutRect,
+    /// Border radii of this rectangle.
+    pub radii: BorderRadius,
+    /// Whether we are clipping inside or outside
+    /// the region.
+    pub mode: ClipMode,
+}
+
+impl BorderRadius {
+    pub fn zero() -> BorderRadius {
+        BorderRadius {
+            top_left: LayoutSize::new(0.0, 0.0),
+            top_right: LayoutSize::new(0.0, 0.0),
+            bottom_left: LayoutSize::new(0.0, 0.0),
+            bottom_right: LayoutSize::new(0.0, 0.0),
+        }
+    }
+
+    pub fn uniform(radius: f32) -> BorderRadius {
+        BorderRadius {
+            top_left: LayoutSize::new(radius, radius),
+            top_right: LayoutSize::new(radius, radius),
+            bottom_left: LayoutSize::new(radius, radius),
+            bottom_right: LayoutSize::new(radius, radius),
+        }
+    }
+
+    pub fn uniform_size(radius: LayoutSize) -> BorderRadius {
+        BorderRadius {
+            top_left: radius,
+            top_right: radius,
+            bottom_left: radius,
+            bottom_right: radius,
+        }
+    }
+
+    pub fn is_uniform(&self) -> Option<f32> {
+        match self.is_uniform_size() {
+            Some(radius) if radius.width == radius.height => Some(radius.width),
+            _ => None,
+        }
+    }
+
+    pub fn is_uniform_size(&self) -> Option<LayoutSize> {
+        let uniform_radius = self.top_left;
+        if self.top_right == uniform_radius && self.bottom_left == uniform_radius &&
+            self.bottom_right == uniform_radius
+        {
+            Some(uniform_radius)
+        } else {
+            None
+        }
+    }
+
+    /// Return whether, in each corner, the radius in *either* direction is zero.
+    /// This means that none of the corners are rounded.
+    pub fn is_zero(&self) -> bool {
+        let corner_is_zero = |corner: &LayoutSize| corner.width == 0.0 || corner.height == 0.0;
+        corner_is_zero(&self.top_left) &&
+        corner_is_zero(&self.top_right) &&
+        corner_is_zero(&self.bottom_right) &&
+        corner_is_zero(&self.bottom_left)
+    }
+}
+
+impl ComplexClipRegion {
+    /// Create a new complex clip region.
+    pub fn new(
+        rect: LayoutRect,
+        radii: BorderRadius,
+        mode: ClipMode,
+    ) -> Self {
+        ComplexClipRegion { rect, radii, mode }
+    }
+}
+
+impl ComplexClipRegion {
+    /// Get a local clipping rect contributed by this clip region.
+    pub fn get_local_clip_rect(&self) -> Option<LayoutRect> {
+        match self.mode {
+            ClipMode::Clip => {
+                Some(self.rect)
+            }
+            ClipMode::ClipOut => {
+                None
+            }
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, Hash, PartialEq, Serialize, PeekPoke)]
+pub struct ClipChainId(pub u64, pub PipelineId);
+
+/// A reference to a clipping node defining how an item is clipped.
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, PartialEq, Serialize, PeekPoke)]
+pub enum ClipId {
+    Clip(usize, PipelineId),
+    ClipChain(ClipChainId),
+}
+
+const ROOT_CLIP_ID: usize = 0;
+
+impl ClipId {
+    /// Return the root clip ID - effectively doing no clipping.
+    pub fn root(pipeline_id: PipelineId) -> Self {
+        ClipId::Clip(ROOT_CLIP_ID, pipeline_id)
+    }
+
+    /// Return an invalid clip ID - needed in places where we carry
+    /// one but need to not attempt to use it.
+    pub fn invalid() -> Self {
+        ClipId::Clip(!0, PipelineId::dummy())
+    }
+
+    pub fn pipeline_id(&self) -> PipelineId {
+        match *self {
+            ClipId::Clip(_, pipeline_id) |
+            ClipId::ClipChain(ClipChainId(_, pipeline_id)) => pipeline_id,
+        }
+    }
+
+    pub fn is_root(&self) -> bool {
+        match *self {
+            ClipId::Clip(id, _) => id == ROOT_CLIP_ID,
+            ClipId::ClipChain(_) => false,
+        }
+    }
+
+    pub fn is_valid(&self) -> bool {
+        match *self {
+            ClipId::Clip(id, _) => id != !0,
+            _ => true,
+        }
+    }
+}
+
+/// A reference to a spatial node defining item positioning.
+#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, Hash, PartialEq, Serialize, PeekPoke)]
+pub struct SpatialId(pub usize, PipelineId);
+
+const ROOT_REFERENCE_FRAME_SPATIAL_ID: usize = 0;
+const ROOT_SCROLL_NODE_SPATIAL_ID: usize = 1;
+
+impl SpatialId {
+    pub fn new(spatial_node_index: usize, pipeline_id: PipelineId) -> Self {
+        SpatialId(spatial_node_index, pipeline_id)
+    }
+
+    pub fn root_reference_frame(pipeline_id: PipelineId) -> Self {
+        SpatialId(ROOT_REFERENCE_FRAME_SPATIAL_ID, pipeline_id)
+    }
+
+    pub fn root_scroll_node(pipeline_id: PipelineId) -> Self {
+        SpatialId(ROOT_SCROLL_NODE_SPATIAL_ID, pipeline_id)
+    }
+
+    pub fn pipeline_id(&self) -> PipelineId {
+        self.1
+    }
+
+    pub fn is_root_reference_frame(&self) -> bool {
+        self.0 == ROOT_REFERENCE_FRAME_SPATIAL_ID
+    }
+
+    pub fn is_root_scroll_node(&self) -> bool {
+        self.0 == ROOT_SCROLL_NODE_SPATIAL_ID
+    }
+}
+
+/// An external identifier that uniquely identifies a scroll frame independent of its ClipId, which
+/// may change from frame to frame. This should be unique within a pipeline. WebRender makes no
+/// attempt to ensure uniqueness. The zero value is reserved for use by the root scroll node of
+/// every pipeline, which always has an external id.
+///
+/// When setting display lists with the `preserve_frame_state` this id is used to preserve scroll
+/// offsets between different sets of SpatialNodes which are ScrollFrames.
+#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, Hash, PartialEq, Serialize, PeekPoke)]
+#[repr(C)]
+pub struct ExternalScrollId(pub u64, pub PipelineId);
+
+impl ExternalScrollId {
+    pub fn pipeline_id(&self) -> PipelineId {
+        self.1
+    }
+
+    pub fn is_root(&self) -> bool {
+        self.0 == 0
+    }
+}
+
+impl DisplayItem {
+    pub fn debug_name(&self) -> &'static str {
+        match *self {
+            DisplayItem::Border(..) => "border",
+            DisplayItem::BoxShadow(..) => "box_shadow",
+            DisplayItem::ClearRectangle(..) => "clear_rectangle",
+            DisplayItem::HitTest(..) => "hit_test",
+            DisplayItem::RectClip(..) => "rect_clip",
+            DisplayItem::RoundedRectClip(..) => "rounded_rect_clip",
+            DisplayItem::ImageMaskClip(..) => "image_mask_clip",
+            DisplayItem::Clip(..) => "clip",
+            DisplayItem::ClipChain(..) => "clip_chain",
+            DisplayItem::ConicGradient(..) => "conic_gradient",
+            DisplayItem::Gradient(..) => "gradient",
+            DisplayItem::Iframe(..) => "iframe",
+            DisplayItem::Image(..) => "image",
+            DisplayItem::RepeatingImage(..) => "repeating_image",
+            DisplayItem::Line(..) => "line",
+            DisplayItem::PopAllShadows => "pop_all_shadows",
+            DisplayItem::PopReferenceFrame => "pop_reference_frame",
+            DisplayItem::PopStackingContext => "pop_stacking_context",
+            DisplayItem::PushShadow(..) => "push_shadow",
+            DisplayItem::PushReferenceFrame(..) => "push_reference_frame",
+            DisplayItem::PushStackingContext(..) => "push_stacking_context",
+            DisplayItem::SetFilterOps => "set_filter_ops",
+            DisplayItem::SetFilterData => "set_filter_data",
+            DisplayItem::SetFilterPrimitives => "set_filter_primitives",
+            DisplayItem::RadialGradient(..) => "radial_gradient",
+            DisplayItem::Rectangle(..) => "rectangle",
+            DisplayItem::ScrollFrame(..) => "scroll_frame",
+            DisplayItem::SetGradientStops => "set_gradient_stops",
+            DisplayItem::ReuseItems(..) => "reuse_item",
+            DisplayItem::RetainedItems(..) => "retained_items",
+            DisplayItem::StickyFrame(..) => "sticky_frame",
+            DisplayItem::Text(..) => "text",
+            DisplayItem::YuvImage(..) => "yuv_image",
+            DisplayItem::BackdropFilter(..) => "backdrop_filter",
+        }
+    }
+}
+
+macro_rules! impl_default_for_enums {
+    ($($enum:ident => $init:expr ),+) => {
+        $(impl Default for $enum {
+            #[allow(unused_imports)]
+            fn default() -> Self {
+                use $enum::*;
+                $init
+            }
+        })*
+    }
+}
+
+impl_default_for_enums! {
+    DisplayItem => PopStackingContext,
+    ScrollSensitivity => ScriptAndInputEvents,
+    LineOrientation => Vertical,
+    LineStyle => Solid,
+    RepeatMode => Stretch,
+    NinePatchBorderSource => Image(ImageKey::default()),
+    BorderDetails => Normal(NormalBorder::default()),
+    BorderRadiusKind => Uniform,
+    BorderStyle => None,
+    BoxShadowClipMode => Outset,
+    ExtendMode => Clamp,
+    FilterOp => Identity,
+    ComponentTransferFuncType => Identity,
+    ClipMode => Clip,
+    ClipId => ClipId::invalid(),
+    ReferenceFrameKind => Transform,
+    Rotation => Degree0,
+    TransformStyle => Flat,
+    RasterSpace => Local(f32::default()),
+    MixBlendMode => Normal,
+    ImageRendering => Auto,
+    AlphaType => Alpha,
+    YuvColorSpace => Rec601,
+    ColorRange => Limited,
+    YuvData => NV12(ImageKey::default(), ImageKey::default()),
+    YuvFormat => NV12,
+    FilterPrimitiveInput => Original,
+    ColorSpace => Srgb,
+    CompositeOperator => Over
+}
diff --git a/gfx/wr/webrender_api/src/display_item_cache.rs b/gfx/wr/webrender_api/src/display_item_cache.rs
new file mode 100644
index 0000000000..169e54797a
--- /dev/null
+++ b/gfx/wr/webrender_api/src/display_item_cache.rs
@@ -0,0 +1,115 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::display_item::*;
+use crate::display_list::*;
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+
+#[derive(Clone, Debug, Deserialize, PartialEq, Serialize)]
+pub struct CachedDisplayItem {
+    item: DisplayItem,
+    data: Vec<u8>,
+}
+
+impl CachedDisplayItem {
+    pub fn display_item(&self) -> &DisplayItem {
+        &self.item
+    }
+
+    pub fn data_as_item_range<T>(&self) -> ItemRange<T> {
+        ItemRange::new(&self.data)
+    }
+}
+
+impl MallocSizeOf for CachedDisplayItem {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        self.data.size_of(ops)
+    }
+}
+
+impl From<DisplayItemRef<'_, '_>> for CachedDisplayItem {
+    fn from(item_ref: DisplayItemRef) -> Self {
+        let item = item_ref.item();
+
+        match item {
+            DisplayItem::Text(..) => CachedDisplayItem {
+                item: *item,
+                data: item_ref.glyphs().bytes().to_vec(),
+            },
+            _ => CachedDisplayItem {
+                item: *item,
+                data: Vec::new(),
+            },
+        }
+    }
+}
+
+#[derive(Clone, Deserialize, MallocSizeOf, Serialize)]
+struct CacheEntry {
+    items: Vec<CachedDisplayItem>,
+    occupied: bool,
+}
+
+#[derive(Clone, Deserialize, MallocSizeOf, Serialize)]
+pub struct DisplayItemCache {
+    entries: Vec<CacheEntry>,
+}
+
+impl DisplayItemCache {
+    fn add_item(&mut self, key: ItemKey, item: CachedDisplayItem) {
+        let mut entry = &mut self.entries[key as usize];
+        entry.items.push(item);
+        entry.occupied = true;
+    }
+
+    fn clear_entry(&mut self, key: ItemKey) {
+        let mut entry = &mut self.entries[key as usize];
+        entry.items.clear();
+        entry.occupied = false;
+    }
+
+    fn grow_if_needed(&mut self, capacity: usize) {
+        if capacity > self.entries.len() {
+            self.entries.resize_with(capacity, || CacheEntry {
+                items: Vec::new(),
+                occupied: false,
+            });
+        }
+    }
+
+    pub fn get_items(&self, key: ItemKey) -> &[CachedDisplayItem] {
+        let entry = &self.entries[key as usize];
+        debug_assert!(entry.occupied);
+        entry.items.as_slice()
+    }
+
+    pub fn new() -> Self {
+        Self {
+            entries: Vec::new(),
+        }
+    }
+
+    pub fn update(&mut self, display_list: &BuiltDisplayList) {
+        self.grow_if_needed(display_list.cache_size());
+
+        let mut iter = display_list.extra_data_iter();
+        let mut current_key: Option<ItemKey> = None;
+        loop {
+            let item = match iter.next() {
+                Some(item) => item,
+                None => break,
+            };
+
+            if let DisplayItem::RetainedItems(key) = item.item() {
+                current_key = Some(*key);
+                self.clear_entry(*key);
+                continue;
+            }
+
+            let key = current_key.expect("Missing RetainedItems marker");
+            let cached_item = CachedDisplayItem::from(item);
+            self.add_item(key, cached_item);
+        }
+    }
+}
diff --git a/gfx/wr/webrender_api/src/display_list.rs b/gfx/wr/webrender_api/src/display_list.rs
new file mode 100644
index 0000000000..0803f302ca
--- /dev/null
+++ b/gfx/wr/webrender_api/src/display_list.rs
@@ -0,0 +1,1996 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use euclid::SideOffsets2D;
+use peek_poke::{ensure_red_zone, peek_from_slice, poke_extend_vec, strip_red_zone};
+use peek_poke::{poke_inplace_slice, poke_into_vec, Poke};
+#[cfg(feature = "deserialize")]
+use serde::de::Deserializer;
+#[cfg(feature = "serialize")]
+use serde::ser::{Serializer, SerializeSeq};
+use serde::{Deserialize, Serialize};
+use std::io::Write;
+use std::marker::PhantomData;
+use std::ops::Range;
+use std::mem;
+use std::collections::HashMap;
+use time::precise_time_ns;
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+// local imports
+use crate::display_item as di;
+use crate::display_item_cache::*;
+use crate::{PipelineId, PropertyBinding};
+use crate::gradient_builder::GradientBuilder;
+use crate::color::ColorF;
+use crate::font::{FontInstanceKey, GlyphInstance, GlyphOptions};
+use crate::image::{ColorDepth, ImageKey};
+use crate::units::*;
+
+
+// We don't want to push a long text-run. If a text-run is too long, split it into several parts.
+// This needs to be set to (renderer::MAX_VERTEX_TEXTURE_WIDTH - VECS_PER_TEXT_RUN) * 2
+pub const MAX_TEXT_RUN_LENGTH: usize = 2040;
+
+// See ROOT_REFERENCE_FRAME_SPATIAL_ID and ROOT_SCROLL_NODE_SPATIAL_ID
+// TODO(mrobinson): It would be a good idea to eliminate the root scroll frame which is only
+// used by Servo.
+const FIRST_SPATIAL_NODE_INDEX: usize = 2;
+
+// See ROOT_SCROLL_NODE_SPATIAL_ID
+const FIRST_CLIP_NODE_INDEX: usize = 1;
+
+#[repr(C)]
+#[derive(Debug, Deserialize, Eq, Hash, PartialEq, Serialize)]
+pub struct ItemRange<'a, T> {
+    bytes: &'a [u8],
+    _boo: PhantomData<T>,
+}
+
+impl<'a, T> Copy for ItemRange<'a, T> {}
+impl<'a, T> Clone for ItemRange<'a, T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<'a, T> Default for ItemRange<'a, T> {
+    fn default() -> Self {
+        ItemRange {
+            bytes: Default::default(),
+            _boo: PhantomData,
+        }
+    }
+}
+
+impl<'a, T> ItemRange<'a, T> {
+    pub fn new(bytes: &'a [u8]) -> Self {
+        Self {
+            bytes,
+            _boo: PhantomData
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        // Nothing more than space for a length (0).
+        self.bytes.len() <= mem::size_of::<usize>()
+    }
+
+    pub fn bytes(&self) -> &[u8] {
+        &self.bytes
+    }
+}
+
+impl<'a, T: Default> ItemRange<'a, T> {
+    pub fn iter(&self) -> AuxIter<'a, T> {
+        AuxIter::new(T::default(), self.bytes)
+    }
+}
+
+impl<'a, T> IntoIterator for ItemRange<'a, T>
+where
+    T: Copy + Default + peek_poke::Peek,
+{
+    type Item = T;
+    type IntoIter = AuxIter<'a, T>;
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+#[derive(Copy, Clone)]
+pub struct TempFilterData<'a> {
+    pub func_types: ItemRange<'a, di::ComponentTransferFuncType>,
+    pub r_values: ItemRange<'a, f32>,
+    pub g_values: ItemRange<'a, f32>,
+    pub b_values: ItemRange<'a, f32>,
+    pub a_values: ItemRange<'a, f32>,
+}
+
+/// A display list.
+#[derive(Clone, Default)]
+pub struct BuiltDisplayList {
+    /// Serde encoded bytes. Mostly DisplayItems, but some mixed in slices.
+    data: Vec<u8>,
+    descriptor: BuiltDisplayListDescriptor,
+}
+
+/// Describes the memory layout of a display list.
+///
+/// A display list consists of some number of display list items, followed by a number of display
+/// items.
+#[repr(C)]
+#[derive(Copy, Clone, Default, Deserialize, Serialize)]
+pub struct BuiltDisplayListDescriptor {
+    /// The first IPC time stamp: before any work has been done
+    builder_start_time: u64,
+    /// The second IPC time stamp: after serialization
+    builder_finish_time: u64,
+    /// The third IPC time stamp: just before sending
+    send_start_time: u64,
+    /// The amount of clipping nodes created while building this display list.
+    total_clip_nodes: usize,
+    /// The amount of spatial nodes created while building this display list.
+    total_spatial_nodes: usize,
+    /// The size of the cache for this display list.
+    cache_size: usize,
+    /// The offset for additional display list data.
+    extra_data_offset: usize,
+}
+
+#[derive(Clone)]
+pub struct DisplayListWithCache {
+    display_list: BuiltDisplayList,
+    cache: DisplayItemCache,
+}
+
+impl DisplayListWithCache {
+    pub fn iter(&self) -> BuiltDisplayListIter {
+        self.display_list.iter_with_cache(&self.cache)
+    }
+
+    pub fn new_from_list(display_list: BuiltDisplayList) -> Self {
+        let mut cache = DisplayItemCache::new();
+        cache.update(&display_list);
+
+        DisplayListWithCache {
+            display_list,
+            cache
+        }
+    }
+
+    pub fn update(&mut self, display_list: BuiltDisplayList) {
+        self.cache.update(&display_list);
+        self.display_list = display_list;
+    }
+
+    pub fn descriptor(&self) -> &BuiltDisplayListDescriptor {
+        self.display_list.descriptor()
+    }
+
+    pub fn data(&self) -> &[u8] {
+        self.display_list.data()
+    }
+}
+
+impl MallocSizeOf for DisplayListWithCache {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        self.display_list.data.size_of(ops) + self.cache.size_of(ops)
+    }
+}
+
+#[cfg(feature = "serialize")]
+impl Serialize for DisplayListWithCache {
+    fn serialize<S: Serializer>(
+        &self,
+        serializer: S
+    ) -> Result<S::Ok, S::Error> {
+        BuiltDisplayList::serialize_with_iterator(serializer, self.iter())
+    }
+}
+
+#[cfg(feature = "deserialize")]
+impl<'de> Deserialize<'de> for DisplayListWithCache {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let display_list = BuiltDisplayList::deserialize(deserializer)?;
+        let cache = DisplayItemCache::new();
+
+        Ok(DisplayListWithCache {
+            display_list,
+            cache,
+        })
+    }
+}
+
+impl BuiltDisplayListDescriptor {}
+
+pub struct BuiltDisplayListIter<'a> {
+    list: &'a BuiltDisplayList,
+    data: &'a [u8],
+    cache: Option<&'a DisplayItemCache>,
+    pending_items: std::slice::Iter<'a, CachedDisplayItem>,
+    cur_cached_item: Option<&'a CachedDisplayItem>,
+    cur_item: di::DisplayItem,
+    cur_stops: ItemRange<'a, di::GradientStop>,
+    cur_glyphs: ItemRange<'a, GlyphInstance>,
+    cur_filters: ItemRange<'a, di::FilterOp>,
+    cur_filter_data: Vec<TempFilterData<'a>>,
+    cur_filter_primitives: ItemRange<'a, di::FilterPrimitive>,
+    cur_clip_chain_items: ItemRange<'a, di::ClipId>,
+    cur_complex_clip: ItemRange<'a, di::ComplexClipRegion>,
+    peeking: Peek,
+    /// Should just be initialized but never populated in release builds
+    debug_stats: DebugStats,
+}
+
+/// Internal info used for more detailed analysis of serialized display lists
+#[allow(dead_code)]
+struct DebugStats {
+    /// Last address in the buffer we pointed to, for computing serialized sizes
+    last_addr: usize,
+    stats: HashMap<&'static str, ItemStats>,
+}
+
+impl DebugStats {
+    #[cfg(feature = "display_list_stats")]
+    fn _update_entry(&mut self, name: &'static str, item_count: usize, byte_count: usize) {
+        let entry = self.stats.entry(name).or_default();
+        entry.total_count += item_count;
+        entry.num_bytes += byte_count;
+    }
+
+    /// Computes the number of bytes we've processed since we last called
+    /// this method, so we can compute the serialized size of a display item.
+    #[cfg(feature = "display_list_stats")]
+    fn debug_num_bytes(&mut self, data: &[u8]) -> usize {
+        let old_addr = self.last_addr;
+        let new_addr = data.as_ptr() as usize;
+        let delta = new_addr - old_addr;
+        self.last_addr = new_addr;
+
+        delta
+    }
+
+    /// Logs stats for the last deserialized display item
+    #[cfg(feature = "display_list_stats")]
+    fn log_item(&mut self, data: &[u8], item: &di::DisplayItem) {
+        let num_bytes = self.debug_num_bytes(data);
+        self._update_entry(item.debug_name(), 1, num_bytes);
+    }
+
+    /// Logs the stats for the given serialized slice
+    #[cfg(feature = "display_list_stats")]
+    fn log_slice<T: Copy + Default + peek_poke::Peek>(
+        &mut self,
+        slice_name: &'static str,
+        range: &ItemRange<T>,
+    ) {
+        // Run this so log_item_stats is accurate, but ignore its result
+        // because log_slice_stats may be called after multiple slices have been
+        // processed, and the `range` has everything we need.
+        self.last_addr = range.bytes.as_ptr() as usize + range.bytes.len();
+
+        self._update_entry(slice_name, range.iter().len(), range.bytes.len());
+    }
+
+    #[cfg(not(feature = "display_list_stats"))]
+    fn log_slice<T>(&mut self, _slice_name: &str, _range: &ItemRange<T>) {
+        /* no-op */
+    }
+}
+
+/// Stats for an individual item
+#[derive(Copy, Clone, Debug, Default)]
+pub struct ItemStats {
+    /// How many instances of this kind of item we deserialized
+    pub total_count: usize,
+    /// How many bytes we processed for this kind of item
+    pub num_bytes: usize,
+}
+
+pub struct DisplayItemRef<'a: 'b, 'b> {
+    iter: &'b BuiltDisplayListIter<'a>,
+}
+
+// Some of these might just become ItemRanges
+impl<'a, 'b> DisplayItemRef<'a, 'b> {
+    pub fn display_list(&self) -> &BuiltDisplayList {
+        self.iter.display_list()
+    }
+
+    // Creates a new iterator where this element's iterator is, to hack around borrowck.
+    pub fn sub_iter(&self) -> BuiltDisplayListIter<'a> {
+        self.iter.sub_iter()
+    }
+
+    pub fn item(&self) -> &di::DisplayItem {
+       self.iter.current_item()
+    }
+
+    pub fn clip_chain_items(&self) -> ItemRange<di::ClipId> {
+        self.iter.cur_clip_chain_items
+    }
+
+    pub fn complex_clip(&self) -> ItemRange<di::ComplexClipRegion> {
+        self.iter.cur_complex_clip
+    }
+
+    pub fn glyphs(&self) -> ItemRange<GlyphInstance> {
+        self.iter.glyphs()
+    }
+
+    pub fn gradient_stops(&self) -> ItemRange<di::GradientStop> {
+        self.iter.gradient_stops()
+    }
+
+    pub fn filters(&self) -> ItemRange<di::FilterOp> {
+        self.iter.cur_filters
+    }
+
+    pub fn filter_datas(&self) -> &Vec<TempFilterData> {
+        &self.iter.cur_filter_data
+    }
+
+    pub fn filter_primitives(&self) -> ItemRange<di::FilterPrimitive> {
+        self.iter.cur_filter_primitives
+    }
+}
+
+#[derive(PartialEq)]
+enum Peek {
+    StartPeeking,
+    IsPeeking,
+    NotPeeking,
+}
+
+#[derive(Clone)]
+pub struct AuxIter<'a, T> {
+    item: T,
+    data: &'a [u8],
+    size: usize,
+//    _boo: PhantomData<T>,
+}
+
+impl BuiltDisplayList {
+    pub fn from_data(data: Vec<u8>, descriptor: BuiltDisplayListDescriptor) -> Self {
+        BuiltDisplayList { data, descriptor }
+    }
+
+    pub fn into_data(self) -> (Vec<u8>, BuiltDisplayListDescriptor) {
+        (self.data, self.descriptor)
+    }
+
+    pub fn data(&self) -> &[u8] {
+        &self.data[..]
+    }
+
+    pub fn item_slice(&self) -> &[u8] {
+        &self.data[..self.descriptor.extra_data_offset]
+    }
+
+    pub fn extra_slice(&self) -> &[u8] {
+        &self.data[self.descriptor.extra_data_offset..]
+    }
+
+    pub fn descriptor(&self) -> &BuiltDisplayListDescriptor {
+        &self.descriptor
+    }
+
+    pub fn set_send_time_ns(&mut self, time: u64) {
+        self.descriptor.send_start_time = time;
+    }
+
+    pub fn times(&self) -> (u64, u64, u64) {
+        (
+            self.descriptor.builder_start_time,
+            self.descriptor.builder_finish_time,
+            self.descriptor.send_start_time,
+        )
+    }
+
+    pub fn total_clip_nodes(&self) -> usize {
+        self.descriptor.total_clip_nodes
+    }
+
+    pub fn total_spatial_nodes(&self) -> usize {
+        self.descriptor.total_spatial_nodes
+    }
+
+    pub fn iter(&self) -> BuiltDisplayListIter {
+        BuiltDisplayListIter::new(self, self.item_slice(), None)
+    }
+
+    pub fn extra_data_iter(&self) -> BuiltDisplayListIter {
+        BuiltDisplayListIter::new(self, self.extra_slice(), None)
+    }
+
+    pub fn iter_with_cache<'a>(
+        &'a self,
+        cache: &'a DisplayItemCache
+    ) -> BuiltDisplayListIter<'a> {
+        BuiltDisplayListIter::new(self, self.item_slice(), Some(cache))
+    }
+
+    pub fn cache_size(&self) -> usize {
+        self.descriptor.cache_size
+    }
+
+    #[cfg(feature = "serialize")]
+    pub fn serialize_with_iterator<S: Serializer>(
+        serializer: S,
+        mut iterator: BuiltDisplayListIter,
+    ) -> Result<S::Ok, S::Error> {
+        use crate::display_item::DisplayItem as Real;
+        use crate::display_item::DebugDisplayItem as Debug;
+
+        let mut seq = serializer.serialize_seq(None)?;
+
+        while let Some(item) = iterator.next_raw() {
+            let serial_di = match *item.item() {
+                Real::Clip(v) => Debug::Clip(
+                    v,
+                    item.iter.cur_complex_clip.iter().collect()
+                ),
+                Real::ClipChain(v) => Debug::ClipChain(
+                    v,
+                    item.iter.cur_clip_chain_items.iter().collect()
+                ),
+                Real::ScrollFrame(v) => Debug::ScrollFrame(v),
+                Real::Text(v) => Debug::Text(
+                    v,
+                    item.iter.cur_glyphs.iter().collect()
+                ),
+                Real::SetFilterOps => Debug::SetFilterOps(
+                    item.iter.cur_filters.iter().collect()
+                ),
+                Real::SetFilterData => {
+                    debug_assert!(!item.iter.cur_filter_data.is_empty(),
+                        "next_raw should have populated cur_filter_data");
+                    let temp_filter_data = &item.iter.cur_filter_data[item.iter.cur_filter_data.len()-1];
+
+                    let func_types: Vec<di::ComponentTransferFuncType> =
+                        temp_filter_data.func_types.iter().collect();
+                    debug_assert!(func_types.len() == 4,
+                        "someone changed the number of filter funcs without updating this code");
+                    Debug::SetFilterData(di::FilterData {
+                        func_r_type: func_types[0],
+                        r_values: temp_filter_data.r_values.iter().collect(),
+                        func_g_type: func_types[1],
+                        g_values: temp_filter_data.g_values.iter().collect(),
+                        func_b_type: func_types[2],
+                        b_values: temp_filter_data.b_values.iter().collect(),
+                        func_a_type: func_types[3],
+                        a_values: temp_filter_data.a_values.iter().collect(),
+                    })
+                },
+                Real::SetFilterPrimitives => Debug::SetFilterPrimitives(
+                    item.iter.cur_filter_primitives.iter().collect()
+                ),
+                Real::SetGradientStops => Debug::SetGradientStops(
+                    item.iter.cur_stops.iter().collect()
+                ),
+                Real::RectClip(v) => Debug::RectClip(v),
+                Real::RoundedRectClip(v) => Debug::RoundedRectClip(v),
+                Real::ImageMaskClip(v) => Debug::ImageMaskClip(v),
+                Real::StickyFrame(v) => Debug::StickyFrame(v),
+                Real::Rectangle(v) => Debug::Rectangle(v),
+                Real::ClearRectangle(v) => Debug::ClearRectangle(v),
+                Real::HitTest(v) => Debug::HitTest(v),
+                Real::Line(v) => Debug::Line(v),
+                Real::Image(v) => Debug::Image(v),
+                Real::RepeatingImage(v) => Debug::RepeatingImage(v),
+                Real::YuvImage(v) => Debug::YuvImage(v),
+                Real::Border(v) => Debug::Border(v),
+                Real::BoxShadow(v) => Debug::BoxShadow(v),
+                Real::Gradient(v) => Debug::Gradient(v),
+                Real::RadialGradient(v) => Debug::RadialGradient(v),
+                Real::ConicGradient(v) => Debug::ConicGradient(v),
+                Real::Iframe(v) => Debug::Iframe(v),
+                Real::PushReferenceFrame(v) => Debug::PushReferenceFrame(v),
+                Real::PushStackingContext(v) => Debug::PushStackingContext(v),
+                Real::PushShadow(v) => Debug::PushShadow(v),
+                Real::BackdropFilter(v) => Debug::BackdropFilter(v),
+
+                Real::PopReferenceFrame => Debug::PopReferenceFrame,
+                Real::PopStackingContext => Debug::PopStackingContext,
+                Real::PopAllShadows => Debug::PopAllShadows,
+                Real::ReuseItems(_) |
+                Real::RetainedItems(_) => unreachable!("Unexpected item"),
+            };
+            seq.serialize_element(&serial_di)?
+        }
+        seq.end()
+    }
+}
+
+/// Returns the byte-range the slice occupied.
+fn skip_slice<'a, T: peek_poke::Peek>(data: &mut &'a [u8]) -> ItemRange<'a, T> {
+    let mut skip_offset = 0usize;
+    *data = peek_from_slice(data, &mut skip_offset);
+    let (skip, rest) = data.split_at(skip_offset);
+
+    // Adjust data pointer to skip read values
+    *data = rest;
+
+    ItemRange {
+        bytes: skip,
+        _boo: PhantomData,
+    }
+}
+
+impl<'a> BuiltDisplayListIter<'a> {
+    pub fn new(
+        list: &'a BuiltDisplayList,
+        data: &'a [u8],
+        cache: Option<&'a DisplayItemCache>,
+    ) -> Self {
+        Self {
+            list,
+            data,
+            cache,
+            pending_items: [].iter(),
+            cur_cached_item: None,
+            cur_item: di::DisplayItem::PopStackingContext,
+            cur_stops: ItemRange::default(),
+            cur_glyphs: ItemRange::default(),
+            cur_filters: ItemRange::default(),
+            cur_filter_data: Vec::new(),
+            cur_filter_primitives: ItemRange::default(),
+            cur_clip_chain_items: ItemRange::default(),
+            cur_complex_clip: ItemRange::default(),
+            peeking: Peek::NotPeeking,
+            debug_stats: DebugStats {
+                last_addr: data.as_ptr() as usize,
+                stats: HashMap::default(),
+            },
+        }
+    }
+
+    pub fn sub_iter(&self) -> Self {
+        let mut iter = BuiltDisplayListIter::new(
+            self.list, self.data, self.cache
+        );
+        iter.pending_items = self.pending_items.clone();
+        iter
+    }
+
+    pub fn display_list(&self) -> &'a BuiltDisplayList {
+        self.list
+    }
+
+    pub fn current_item(&self) -> &di::DisplayItem {
+        match self.cur_cached_item {
+            Some(cached_item) => cached_item.display_item(),
+            None => &self.cur_item
+        }
+    }
+
+    fn cached_item_range_or<T>(
+        &self,
+        data: ItemRange<'a, T>
+    ) -> ItemRange<'a, T> {
+        match self.cur_cached_item {
+            Some(cached_item) => cached_item.data_as_item_range(),
+            None => data,
+        }
+    }
+
+    pub fn glyphs(&self) -> ItemRange<GlyphInstance> {
+        self.cached_item_range_or(self.cur_glyphs)
+    }
+
+    pub fn gradient_stops(&self) -> ItemRange<di::GradientStop> {
+        self.cached_item_range_or(self.cur_stops)
+    }
+
+    fn advance_pending_items(&mut self) -> bool {
+        self.cur_cached_item = self.pending_items.next();
+        self.cur_cached_item.is_some()
+    }
+
+    pub fn next<'b>(&'b mut self) -> Option<DisplayItemRef<'a, 'b>> {
+        use crate::DisplayItem::*;
+
+        match self.peeking {
+            Peek::IsPeeking => {
+                self.peeking = Peek::NotPeeking;
+                return Some(self.as_ref());
+            }
+            Peek::StartPeeking => {
+                self.peeking = Peek::IsPeeking;
+            }
+            Peek::NotPeeking => { /* do nothing */ }
+        }
+
+        // Don't let these bleed into another item
+        self.cur_stops = ItemRange::default();
+        self.cur_complex_clip = ItemRange::default();
+        self.cur_clip_chain_items = ItemRange::default();
+        self.cur_filters = ItemRange::default();
+        self.cur_filter_primitives = ItemRange::default();
+        self.cur_filter_data.clear();
+
+        loop {
+            self.next_raw()?;
+            match self.cur_item {
+                SetGradientStops |
+                SetFilterOps |
+                SetFilterData |
+                SetFilterPrimitives => {
+                    // These are marker items for populating other display items, don't yield them.
+                    continue;
+                }
+                _ => {
+                    break;
+                }
+            }
+        }
+
+        Some(self.as_ref())
+    }
+
+    /// Gets the next display item, even if it's a dummy. Also doesn't handle peeking
+    /// and may leave irrelevant ranges live (so a Clip may have GradientStops if
+    /// for some reason you ask).
+    pub fn next_raw<'b>(&'b mut self) -> Option<DisplayItemRef<'a, 'b>> {
+        use crate::DisplayItem::*;
+
+        if self.advance_pending_items() {
+            return Some(self.as_ref());
+        }
+
+        // A "red zone" of DisplayItem::max_size() bytes has been added to the
+        // end of the serialized display list. If this amount, or less, is
+        // remaining then we've reached the end of the display list.
+        if self.data.len() <= di::DisplayItem::max_size() {
+            return None;
+        }
+
+        self.data = peek_from_slice(self.data, &mut self.cur_item);
+        self.log_item_stats();
+
+        match self.cur_item {
+            SetGradientStops => {
+                self.cur_stops = skip_slice::<di::GradientStop>(&mut self.data);
+                self.debug_stats.log_slice("set_gradient_stops.stops", &self.cur_stops);
+            }
+            SetFilterOps => {
+                self.cur_filters = skip_slice::<di::FilterOp>(&mut self.data);
+                self.debug_stats.log_slice("set_filter_ops.ops", &self.cur_filters);
+            }
+            SetFilterData => {
+                self.cur_filter_data.push(TempFilterData {
+                    func_types: skip_slice::<di::ComponentTransferFuncType>(&mut self.data),
+                    r_values: skip_slice::<f32>(&mut self.data),
+                    g_values: skip_slice::<f32>(&mut self.data),
+                    b_values: skip_slice::<f32>(&mut self.data),
+                    a_values: skip_slice::<f32>(&mut self.data),
+                });
+
+                let data = *self.cur_filter_data.last().unwrap();
+                self.debug_stats.log_slice("set_filter_data.func_types", &data.func_types);
+                self.debug_stats.log_slice("set_filter_data.r_values", &data.r_values);
+                self.debug_stats.log_slice("set_filter_data.g_values", &data.g_values);
+                self.debug_stats.log_slice("set_filter_data.b_values", &data.b_values);
+                self.debug_stats.log_slice("set_filter_data.a_values", &data.a_values);
+            }
+            SetFilterPrimitives => {
+                self.cur_filter_primitives = skip_slice::<di::FilterPrimitive>(&mut self.data);
+                self.debug_stats.log_slice("set_filter_primitives.primitives", &self.cur_filter_primitives);
+            }
+            ClipChain(_) => {
+                self.cur_clip_chain_items = skip_slice::<di::ClipId>(&mut self.data);
+                self.debug_stats.log_slice("clip_chain.clip_ids", &self.cur_clip_chain_items);
+            }
+            Clip(_) => {
+                self.cur_complex_clip = skip_slice::<di::ComplexClipRegion>(&mut self.data);
+                self.debug_stats.log_slice("clip.complex_clips", &self.cur_complex_clip);
+            }
+            Text(_) => {
+                self.cur_glyphs = skip_slice::<GlyphInstance>(&mut self.data);
+                self.debug_stats.log_slice("text.glyphs", &self.cur_glyphs);
+            }
+            ReuseItems(key) => {
+                match self.cache {
+                    Some(cache) => {
+                        self.pending_items = cache.get_items(key).iter();
+                        self.advance_pending_items();
+                    }
+                    None => {
+                        unreachable!("Cache marker without cache!");
+                    }
+                }
+            }
+            _ => { /* do nothing */ }
+        }
+
+        Some(self.as_ref())
+    }
+
+    pub fn as_ref<'b>(&'b self) -> DisplayItemRef<'a, 'b> {
+        DisplayItemRef {
+            iter: self,
+        }
+    }
+
+    pub fn skip_current_stacking_context(&mut self) {
+        let mut depth = 0;
+        while let Some(item) = self.next() {
+            match *item.item() {
+                di::DisplayItem::PushStackingContext(..) => depth += 1,
+                di::DisplayItem::PopStackingContext if depth == 0 => return,
+                di::DisplayItem::PopStackingContext => depth -= 1,
+                _ => {}
+            }
+        }
+    }
+
+    pub fn current_stacking_context_empty(&mut self) -> bool {
+        match self.peek() {
+            Some(item) => *item.item() == di::DisplayItem::PopStackingContext,
+            None => true,
+        }
+    }
+
+    pub fn peek<'b>(&'b mut self) -> Option<DisplayItemRef<'a, 'b>> {
+        if self.peeking == Peek::NotPeeking {
+            self.peeking = Peek::StartPeeking;
+            self.next()
+        } else {
+            Some(self.as_ref())
+        }
+    }
+
+    /// Get the debug stats for what this iterator has deserialized.
+    /// Should always be empty in release builds.
+    pub fn debug_stats(&mut self) -> Vec<(&'static str, ItemStats)> {
+        let mut result = self.debug_stats.stats.drain().collect::<Vec<_>>();
+        result.sort_by_key(|stats| stats.0);
+        result
+    }
+
+    /// Adds the debug stats from another to our own, assuming we are a sub-iter of the other
+    /// (so we can ignore where they were in the traversal).
+    pub fn merge_debug_stats_from(&mut self, other: &mut Self) {
+        for (key, other_entry) in other.debug_stats.stats.iter() {
+            let entry = self.debug_stats.stats.entry(key).or_default();
+
+            entry.total_count += other_entry.total_count;
+            entry.num_bytes += other_entry.num_bytes;
+        }
+    }
+
+    /// Logs stats for the last deserialized display item
+    #[cfg(feature = "display_list_stats")]
+    fn log_item_stats(&mut self) {
+        self.debug_stats.log_item(self.data, &self.cur_item);
+    }
+
+    #[cfg(not(feature = "display_list_stats"))]
+    fn log_item_stats(&mut self) { /* no-op */ }
+}
+
+impl<'a, T> AuxIter<'a, T> {
+    pub fn new(item: T, mut data: &'a [u8]) -> Self {
+        let mut size = 0usize;
+        if !data.is_empty() {
+            data = peek_from_slice(data, &mut size);
+        };
+
+        AuxIter {
+            item,
+            data,
+            size,
+//            _boo: PhantomData,
+        }
+    }
+}
+
+impl<'a, T: Copy + peek_poke::Peek> Iterator for AuxIter<'a, T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.size == 0 {
+            None
+        } else {
+            self.size -= 1;
+            self.data = peek_from_slice(self.data, &mut self.item);
+            Some(self.item)
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.size, Some(self.size))
+    }
+}
+
+impl<'a, T: Copy + peek_poke::Peek> ::std::iter::ExactSizeIterator for AuxIter<'a, T> {}
+
+#[cfg(feature = "serialize")]
+impl Serialize for BuiltDisplayList {
+    fn serialize<S: Serializer>(
+        &self,
+        serializer: S
+    ) -> Result<S::Ok, S::Error> {
+        Self::serialize_with_iterator(serializer, self.iter())
+    }
+}
+
+// The purpose of this implementation is to deserialize
+// a display list from one format just to immediately
+// serialize then into a "built" `Vec<u8>`.
+
+#[cfg(feature = "deserialize")]
+impl<'de> Deserialize<'de> for BuiltDisplayList {
+    fn deserialize<D: Deserializer<'de>>(
+        deserializer: D
+    ) -> Result<Self, D::Error> {
+        use crate::display_item::DisplayItem as Real;
+        use crate::display_item::DebugDisplayItem as Debug;
+
+        let list = Vec::<Debug>::deserialize(deserializer)?;
+
+        let mut data = Vec::new();
+        let mut temp = Vec::new();
+        let mut total_clip_nodes = FIRST_CLIP_NODE_INDEX;
+        let mut total_spatial_nodes = FIRST_SPATIAL_NODE_INDEX;
+        for complete in list {
+            let item = match complete {
+                Debug::Clip(v, complex_clips) => {
+                    total_clip_nodes += 1;
+                    DisplayListBuilder::push_iter_impl(&mut temp, complex_clips);
+                    Real::Clip(v)
+                },
+                Debug::ClipChain(v, clip_chain_ids) => {
+                    DisplayListBuilder::push_iter_impl(&mut temp, clip_chain_ids);
+                    Real::ClipChain(v)
+                }
+                Debug::ScrollFrame(v) => {
+                    total_spatial_nodes += 1;
+                    total_clip_nodes += 1;
+                    Real::ScrollFrame(v)
+                }
+                Debug::StickyFrame(v) => {
+                    total_spatial_nodes += 1;
+                    Real::StickyFrame(v)
+                }
+                Debug::Text(v, glyphs) => {
+                    DisplayListBuilder::push_iter_impl(&mut temp, glyphs);
+                    Real::Text(v)
+                },
+                Debug::Iframe(v) => {
+                    total_clip_nodes += 1;
+                    Real::Iframe(v)
+                }
+                Debug::PushReferenceFrame(v) => {
+                    total_spatial_nodes += 1;
+                    Real::PushReferenceFrame(v)
+                }
+                Debug::SetFilterOps(filters) => {
+                    DisplayListBuilder::push_iter_impl(&mut temp, filters);
+                    Real::SetFilterOps
+                },
+                Debug::SetFilterData(filter_data) => {
+                    let func_types: Vec<di::ComponentTransferFuncType> =
+                        [filter_data.func_r_type,
+                         filter_data.func_g_type,
+                         filter_data.func_b_type,
+                         filter_data.func_a_type].to_vec();
+                    DisplayListBuilder::push_iter_impl(&mut temp, func_types);
+                    DisplayListBuilder::push_iter_impl(&mut temp, filter_data.r_values);
+                    DisplayListBuilder::push_iter_impl(&mut temp, filter_data.g_values);
+                    DisplayListBuilder::push_iter_impl(&mut temp, filter_data.b_values);
+                    DisplayListBuilder::push_iter_impl(&mut temp, filter_data.a_values);
+                    Real::SetFilterData
+                },
+                Debug::SetFilterPrimitives(filter_primitives) => {
+                    DisplayListBuilder::push_iter_impl(&mut temp, filter_primitives);
+                    Real::SetFilterPrimitives
+                }
+                Debug::SetGradientStops(stops) => {
+                    DisplayListBuilder::push_iter_impl(&mut temp, stops);
+                    Real::SetGradientStops
+                },
+                Debug::RectClip(v) => Real::RectClip(v),
+                Debug::RoundedRectClip(v) => Real::RoundedRectClip(v),
+                Debug::ImageMaskClip(v) => Real::ImageMaskClip(v),
+                Debug::Rectangle(v) => Real::Rectangle(v),
+                Debug::ClearRectangle(v) => Real::ClearRectangle(v),
+                Debug::HitTest(v) => Real::HitTest(v),
+                Debug::Line(v) => Real::Line(v),
+                Debug::Image(v) => Real::Image(v),
+                Debug::RepeatingImage(v) => Real::RepeatingImage(v),
+                Debug::YuvImage(v) => Real::YuvImage(v),
+                Debug::Border(v) => Real::Border(v),
+                Debug::BoxShadow(v) => Real::BoxShadow(v),
+                Debug::Gradient(v) => Real::Gradient(v),
+                Debug::RadialGradient(v) => Real::RadialGradient(v),
+                Debug::ConicGradient(v) => Real::ConicGradient(v),
+                Debug::PushStackingContext(v) => Real::PushStackingContext(v),
+                Debug::PushShadow(v) => Real::PushShadow(v),
+                Debug::BackdropFilter(v) => Real::BackdropFilter(v),
+
+                Debug::PopStackingContext => Real::PopStackingContext,
+                Debug::PopReferenceFrame => Real::PopReferenceFrame,
+                Debug::PopAllShadows => Real::PopAllShadows,
+            };
+            poke_into_vec(&item, &mut data);
+            // the aux data is serialized after the item, hence the temporary
+            data.extend(temp.drain(..));
+        }
+
+        // Add `DisplayItem::max_size` zone of zeroes to the end of display list
+        // so there is at least this amount available in the display list during
+        // serialization.
+        ensure_red_zone::<di::DisplayItem>(&mut data);
+        let extra_data_offset = data.len();
+
+        Ok(BuiltDisplayList {
+            data,
+            descriptor: BuiltDisplayListDescriptor {
+                builder_start_time: 0,
+                builder_finish_time: 1,
+                send_start_time: 1,
+                total_clip_nodes,
+                total_spatial_nodes,
+                extra_data_offset,
+                cache_size: 0,
+            },
+        })
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct SaveState {
+    dl_len: usize,
+    next_clip_index: usize,
+    next_spatial_index: usize,
+    next_clip_chain_id: u64,
+}
+
+/// DisplayListSection determines the target buffer for the display items.
+pub enum DisplayListSection {
+    /// The main/default buffer: contains item data and item group markers.
+    Data,
+    /// Auxiliary buffer: contains the item data for item groups.
+    ExtraData,
+    /// Temporary buffer: contains the data for pending item group. Flushed to
+    /// one of the buffers above, after item grouping finishes.
+    Chunk,
+}
+
+#[derive(Clone)]
+pub struct DisplayListBuilder {
+    pub data: Vec<u8>,
+    pub pipeline_id: PipelineId,
+
+    extra_data: Vec<u8>,
+    pending_chunk: Vec<u8>,
+    writing_to_chunk: bool,
+
+    next_clip_index: usize,
+    next_spatial_index: usize,
+    next_clip_chain_id: u64,
+    builder_start_time: u64,
+
+    save_state: Option<SaveState>,
+
+    cache_size: usize,
+    serialized_content_buffer: Option<String>,
+}
+
+impl DisplayListBuilder {
+    pub fn new(pipeline_id: PipelineId) -> Self {
+        Self::with_capacity(pipeline_id, 0)
+    }
+
+    pub fn with_capacity(
+        pipeline_id: PipelineId,
+        capacity: usize,
+    ) -> Self {
+        let start_time = precise_time_ns();
+
+        DisplayListBuilder {
+            data: Vec::with_capacity(capacity),
+            pipeline_id,
+
+            extra_data: Vec::new(),
+            pending_chunk: Vec::new(),
+            writing_to_chunk: false,
+
+            next_clip_index: FIRST_CLIP_NODE_INDEX,
+            next_spatial_index: FIRST_SPATIAL_NODE_INDEX,
+            next_clip_chain_id: 0,
+            builder_start_time: start_time,
+            save_state: None,
+            cache_size: 0,
+            serialized_content_buffer: None,
+        }
+    }
+
+    /// Saves the current display list state, so it may be `restore()`'d.
+    ///
+    /// # Conditions:
+    ///
+    /// * Doesn't support popping clips that were pushed before the save.
+    /// * Doesn't support nested saves.
+    /// * Must call `clear_save()` if the restore becomes unnecessary.
+    pub fn save(&mut self) {
+        assert!(self.save_state.is_none(), "DisplayListBuilder doesn't support nested saves");
+
+        self.save_state = Some(SaveState {
+            dl_len: self.data.len(),
+            next_clip_index: self.next_clip_index,
+            next_spatial_index: self.next_spatial_index,
+            next_clip_chain_id: self.next_clip_chain_id,
+        });
+    }
+
+    /// Restores the state of the builder to when `save()` was last called.
+    pub fn restore(&mut self) {
+        let state = self.save_state.take().expect("No save to restore DisplayListBuilder from");
+
+        self.data.truncate(state.dl_len);
+        self.next_clip_index = state.next_clip_index;
+        self.next_spatial_index = state.next_spatial_index;
+        self.next_clip_chain_id = state.next_clip_chain_id;
+    }
+
+    /// Discards the builder's save (indicating the attempted operation was successful).
+    pub fn clear_save(&mut self) {
+        self.save_state.take().expect("No save to clear in DisplayListBuilder");
+    }
+
+    /// Emits a debug representation of display items in the list, for debugging
+    /// purposes. If the range's start parameter is specified, only display
+    /// items starting at that index (inclusive) will be printed. If the range's
+    /// end parameter is specified, only display items before that index
+    /// (exclusive) will be printed. Calling this function with end <= start is
+    /// allowed but is just a waste of CPU cycles. The function emits the
+    /// debug representation of the selected display items, one per line, with
+    /// the given indent, to the provided sink object. The return value is
+    /// the total number of items in the display list, which allows the
+    /// caller to subsequently invoke this function to only dump the newly-added
+    /// items.
+    pub fn emit_display_list<W>(
+        &mut self,
+        indent: usize,
+        range: Range<Option<usize>>,
+        mut sink: W,
+    ) -> usize
+    where
+        W: Write
+    {
+        let mut temp = BuiltDisplayList::default();
+        ensure_red_zone::<di::DisplayItem>(&mut self.data);
+        temp.descriptor.extra_data_offset = self.data.len();
+        mem::swap(&mut temp.data, &mut self.data);
+
+        let mut index: usize = 0;
+        {
+            let mut cache = DisplayItemCache::new();
+            cache.update(&temp);
+            let mut iter = temp.iter_with_cache(&cache);
+            while let Some(item) = iter.next_raw() {
+                if index >= range.start.unwrap_or(0) && range.end.map_or(true, |e| index < e) {
+                    writeln!(sink, "{}{:?}", "  ".repeat(indent), item.item()).unwrap();
+                }
+                index += 1;
+            }
+        }
+
+        self.data = temp.data;
+        strip_red_zone::<di::DisplayItem>(&mut self.data);
+        index
+    }
+
+    /// Print the display items in the list to stdout.
+    pub fn dump_serialized_display_list(&mut self) {
+        self.serialized_content_buffer = Some(String::new());
+    }
+
+    fn add_to_display_list_dump<T: std::fmt::Debug>(&mut self, item: T) {
+        if let Some(ref mut content) = self.serialized_content_buffer {
+            use std::fmt::Write;
+            write!(content, "{:?}\n", item).expect("DL dump write failed.");
+        }
+    }
+
+    /// Returns the default section that DisplayListBuilder will write to,
+    /// if no section is specified explicitly.
+    fn default_section(&self) -> DisplayListSection {
+        if self.writing_to_chunk {
+            DisplayListSection::Chunk
+        } else {
+            DisplayListSection::Data
+        }
+    }
+
+    fn buffer_from_section(
+        &mut self,
+        section: DisplayListSection
+    ) -> &mut Vec<u8> {
+        match section {
+            DisplayListSection::Data => &mut self.data,
+            DisplayListSection::ExtraData => &mut self.extra_data,
+            DisplayListSection::Chunk => &mut self.pending_chunk,
+        }
+    }
+
+    #[inline]
+    pub fn push_item_to_section(
+        &mut self,
+        item: &di::DisplayItem,
+        section: DisplayListSection,
+    ) {
+        poke_into_vec(item, self.buffer_from_section(section));
+        self.add_to_display_list_dump(item);
+    }
+
+    /// Add an item to the display list.
+    ///
+    /// NOTE: It is usually preferable to use the specialized methods to push
+    /// display items. Pushing unexpected or invalid items here may
+    /// result in WebRender panicking or behaving in unexpected ways.
+    #[inline]
+    pub fn push_item(&mut self, item: &di::DisplayItem) {
+        self.push_item_to_section(item, self.default_section());
+    }
+
+    fn push_iter_impl<I>(data: &mut Vec<u8>, iter_source: I)
+    where
+        I: IntoIterator,
+        I::IntoIter: ExactSizeIterator,
+        I::Item: Poke,
+    {
+        let iter = iter_source.into_iter();
+        let len = iter.len();
+        // Format:
+        // payload_byte_size: usize, item_count: usize, [I; item_count]
+
+        // Track the the location of where to write byte size with offsets
+        // instead of pointers because data may be moved in memory during
+        // `serialize_iter_fast`.
+        let byte_size_offset = data.len();
+
+        // We write a dummy value so there's room for later
+        poke_into_vec(&0usize, data);
+        poke_into_vec(&len, data);
+        let count = poke_extend_vec(iter, data);
+        debug_assert_eq!(len, count, "iterator.len() returned two different values");
+
+        // Add red zone
+        ensure_red_zone::<I::Item>(data);
+
+        // Now write the actual byte_size
+        let final_offset = data.len();
+        debug_assert!(final_offset >= (byte_size_offset + mem::size_of::<usize>()),
+            "space was never allocated for this array's byte_size");
+        let byte_size = final_offset - byte_size_offset - mem::size_of::<usize>();
+        poke_inplace_slice(&byte_size, &mut data[byte_size_offset..]);
+    }
+
+    /// Push items from an iterator to the display list.
+    ///
+    /// NOTE: Pushing unexpected or invalid items to the display list
+    /// may result in panic and confusion.
+    pub fn push_iter<I>(&mut self, iter: I)
+    where
+        I: IntoIterator,
+        I::IntoIter: ExactSizeIterator,
+        I::Item: Poke,
+    {
+        let mut buffer = self.buffer_from_section(self.default_section());
+        Self::push_iter_impl(&mut buffer, iter);
+    }
+
+    pub fn push_rect(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        color: ColorF,
+    ) {
+        let item = di::DisplayItem::Rectangle(di::RectangleDisplayItem {
+            common: *common,
+            color: PropertyBinding::Value(color),
+            bounds,
+        });
+        self.push_item(&item);
+    }
+
+    pub fn push_rect_with_animation(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        color: PropertyBinding<ColorF>,
+    ) {
+        let item = di::DisplayItem::Rectangle(di::RectangleDisplayItem {
+            common: *common,
+            color,
+            bounds,
+        });
+        self.push_item(&item);
+    }
+
+    pub fn push_clear_rect(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+    ) {
+        let item = di::DisplayItem::ClearRectangle(di::ClearRectangleDisplayItem {
+            common: *common,
+            bounds,
+        });
+        self.push_item(&item);
+    }
+
+    pub fn push_hit_test(
+        &mut self,
+        common: &di::CommonItemProperties,
+        tag: di::ItemTag,
+    ) {
+        let item = di::DisplayItem::HitTest(di::HitTestDisplayItem {
+            common: *common,
+            tag,
+        });
+        self.push_item(&item);
+    }
+
+    pub fn push_line(
+        &mut self,
+        common: &di::CommonItemProperties,
+        area: &LayoutRect,
+        wavy_line_thickness: f32,
+        orientation: di::LineOrientation,
+        color: &ColorF,
+        style: di::LineStyle,
+    ) {
+        let item = di::DisplayItem::Line(di::LineDisplayItem {
+            common: *common,
+            area: *area,
+            wavy_line_thickness,
+            orientation,
+            color: *color,
+            style,
+        });
+
+        self.push_item(&item);
+    }
+
+    pub fn push_image(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        image_rendering: di::ImageRendering,
+        alpha_type: di::AlphaType,
+        key: ImageKey,
+        color: ColorF,
+    ) {
+        let item = di::DisplayItem::Image(di::ImageDisplayItem {
+            common: *common,
+            bounds,
+            image_key: key,
+            image_rendering,
+            alpha_type,
+            color,
+        });
+
+        self.push_item(&item);
+    }
+
+    pub fn push_repeating_image(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        stretch_size: LayoutSize,
+        tile_spacing: LayoutSize,
+        image_rendering: di::ImageRendering,
+        alpha_type: di::AlphaType,
+        key: ImageKey,
+        color: ColorF,
+    ) {
+        let item = di::DisplayItem::RepeatingImage(di::RepeatingImageDisplayItem {
+            common: *common,
+            bounds,
+            image_key: key,
+            stretch_size,
+            tile_spacing,
+            image_rendering,
+            alpha_type,
+            color,
+        });
+
+        self.push_item(&item);
+    }
+
+    /// Push a yuv image. All planar data in yuv image should use the same buffer type.
+    pub fn push_yuv_image(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        yuv_data: di::YuvData,
+        color_depth: ColorDepth,
+        color_space: di::YuvColorSpace,
+        color_range: di::ColorRange,
+        image_rendering: di::ImageRendering,
+    ) {
+        let item = di::DisplayItem::YuvImage(di::YuvImageDisplayItem {
+            common: *common,
+            bounds,
+            yuv_data,
+            color_depth,
+            color_space,
+            color_range,
+            image_rendering,
+        });
+        self.push_item(&item);
+    }
+
+    pub fn push_text(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        glyphs: &[GlyphInstance],
+        font_key: FontInstanceKey,
+        color: ColorF,
+        glyph_options: Option<GlyphOptions>,
+    ) {
+        let item = di::DisplayItem::Text(di::TextDisplayItem {
+            common: *common,
+            bounds,
+            color,
+            font_key,
+            glyph_options,
+        });
+
+        for split_glyphs in glyphs.chunks(MAX_TEXT_RUN_LENGTH) {
+            self.push_item(&item);
+            self.push_iter(split_glyphs);
+        }
+    }
+
+    /// NOTE: gradients must be pushed in the order they're created
+    /// because create_gradient stores the stops in anticipation.
+    pub fn create_gradient(
+        &mut self,
+        start_point: LayoutPoint,
+        end_point: LayoutPoint,
+        stops: Vec<di::GradientStop>,
+        extend_mode: di::ExtendMode,
+    ) -> di::Gradient {
+        let mut builder = GradientBuilder::with_stops(stops);
+        let gradient = builder.gradient(start_point, end_point, extend_mode);
+        self.push_stops(builder.stops());
+        gradient
+    }
+
+    /// NOTE: gradients must be pushed in the order they're created
+    /// because create_gradient stores the stops in anticipation.
+    pub fn create_radial_gradient(
+        &mut self,
+        center: LayoutPoint,
+        radius: LayoutSize,
+        stops: Vec<di::GradientStop>,
+        extend_mode: di::ExtendMode,
+    ) -> di::RadialGradient {
+        let mut builder = GradientBuilder::with_stops(stops);
+        let gradient = builder.radial_gradient(center, radius, extend_mode);
+        self.push_stops(builder.stops());
+        gradient
+    }
+
+    /// NOTE: gradients must be pushed in the order they're created
+    /// because create_gradient stores the stops in anticipation.
+    pub fn create_conic_gradient(
+        &mut self,
+        center: LayoutPoint,
+        angle: f32,
+        stops: Vec<di::GradientStop>,
+        extend_mode: di::ExtendMode,
+    ) -> di::ConicGradient {
+        let mut builder = GradientBuilder::with_stops(stops);
+        let gradient = builder.conic_gradient(center, angle, extend_mode);
+        self.push_stops(builder.stops());
+        gradient
+    }
+
+    pub fn push_border(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        widths: LayoutSideOffsets,
+        details: di::BorderDetails,
+    ) {
+        let item = di::DisplayItem::Border(di::BorderDisplayItem {
+            common: *common,
+            bounds,
+            details,
+            widths,
+        });
+
+        self.push_item(&item);
+    }
+
+    pub fn push_box_shadow(
+        &mut self,
+        common: &di::CommonItemProperties,
+        box_bounds: LayoutRect,
+        offset: LayoutVector2D,
+        color: ColorF,
+        blur_radius: f32,
+        spread_radius: f32,
+        border_radius: di::BorderRadius,
+        clip_mode: di::BoxShadowClipMode,
+    ) {
+        let item = di::DisplayItem::BoxShadow(di::BoxShadowDisplayItem {
+            common: *common,
+            box_bounds,
+            offset,
+            color,
+            blur_radius,
+            spread_radius,
+            border_radius,
+            clip_mode,
+        });
+
+        self.push_item(&item);
+    }
+
+    /// Pushes a linear gradient to be displayed.
+    ///
+    /// The gradient itself is described in the
+    /// `gradient` parameter. It is drawn on
+    /// a "tile" with the dimensions from `tile_size`.
+    /// These tiles are now repeated to the right and
+    /// to the bottom infinitely. If `tile_spacing`
+    /// is not zero spacers with the given dimensions
+    /// are inserted between the tiles as seams.
+    ///
+    /// The origin of the tiles is given in `layout.rect.origin`.
+    /// If the gradient should only be displayed once limit
+    /// the `layout.rect.size` to a single tile.
+    /// The gradient is only visible within the local clip.
+    pub fn push_gradient(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        gradient: di::Gradient,
+        tile_size: LayoutSize,
+        tile_spacing: LayoutSize,
+    ) {
+        let item = di::DisplayItem::Gradient(di::GradientDisplayItem {
+            common: *common,
+            bounds,
+            gradient,
+            tile_size,
+            tile_spacing,
+        });
+
+        self.push_item(&item);
+    }
+
+    /// Pushes a radial gradient to be displayed.
+    ///
+    /// See [`push_gradient`](#method.push_gradient) for explanation.
+    pub fn push_radial_gradient(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        gradient: di::RadialGradient,
+        tile_size: LayoutSize,
+        tile_spacing: LayoutSize,
+    ) {
+        let item = di::DisplayItem::RadialGradient(di::RadialGradientDisplayItem {
+            common: *common,
+            bounds,
+            gradient,
+            tile_size,
+            tile_spacing,
+        });
+
+        self.push_item(&item);
+    }
+
+    /// Pushes a conic gradient to be displayed.
+    ///
+    /// See [`push_gradient`](#method.push_gradient) for explanation.
+    pub fn push_conic_gradient(
+        &mut self,
+        common: &di::CommonItemProperties,
+        bounds: LayoutRect,
+        gradient: di::ConicGradient,
+        tile_size: LayoutSize,
+        tile_spacing: LayoutSize,
+    ) {
+        let item = di::DisplayItem::ConicGradient(di::ConicGradientDisplayItem {
+            common: *common,
+            bounds,
+            gradient,
+            tile_size,
+            tile_spacing,
+        });
+
+        self.push_item(&item);
+    }
+
+    pub fn push_reference_frame(
+        &mut self,
+        origin: LayoutPoint,
+        parent_spatial_id: di::SpatialId,
+        transform_style: di::TransformStyle,
+        transform: PropertyBinding<LayoutTransform>,
+        kind: di::ReferenceFrameKind,
+    ) -> di::SpatialId {
+        let id = self.generate_spatial_index();
+
+        let item = di::DisplayItem::PushReferenceFrame(di::ReferenceFrameDisplayListItem {
+            parent_spatial_id,
+            origin,
+            reference_frame: di::ReferenceFrame {
+                transform_style,
+                transform: di::ReferenceTransformBinding::Static {
+                    binding: transform,
+                },
+                kind,
+                id,
+            },
+        });
+
+        self.push_item(&item);
+        id
+    }
+
+    pub fn push_computed_frame(
+        &mut self,
+        origin: LayoutPoint,
+        parent_spatial_id: di::SpatialId,
+        scale_from: Option<LayoutSize>,
+        vertical_flip: bool,
+        rotation: di::Rotation,
+    ) -> di::SpatialId {
+        let id = self.generate_spatial_index();
+
+        let item = di::DisplayItem::PushReferenceFrame(di::ReferenceFrameDisplayListItem {
+            parent_spatial_id,
+            origin,
+            reference_frame: di::ReferenceFrame {
+                transform_style: di::TransformStyle::Flat,
+                transform: di::ReferenceTransformBinding::Computed {
+                    scale_from,
+                    vertical_flip,
+                    rotation,
+                },
+                kind: di::ReferenceFrameKind::Transform,
+                id,
+            },
+        });
+
+        self.push_item(&item);
+        id
+    }
+
+    pub fn pop_reference_frame(&mut self) {
+        self.push_item(&di::DisplayItem::PopReferenceFrame);
+    }
+
+    pub fn push_stacking_context(
+        &mut self,
+        origin: LayoutPoint,
+        spatial_id: di::SpatialId,
+        prim_flags: di::PrimitiveFlags,
+        clip_id: Option<di::ClipId>,
+        transform_style: di::TransformStyle,
+        mix_blend_mode: di::MixBlendMode,
+        filters: &[di::FilterOp],
+        filter_datas: &[di::FilterData],
+        filter_primitives: &[di::FilterPrimitive],
+        raster_space: di::RasterSpace,
+        flags: di::StackingContextFlags,
+    ) {
+        self.push_filters(filters, filter_datas, filter_primitives);
+
+        let item = di::DisplayItem::PushStackingContext(di::PushStackingContextDisplayItem {
+            origin,
+            spatial_id,
+            prim_flags,
+            stacking_context: di::StackingContext {
+                transform_style,
+                mix_blend_mode,
+                clip_id,
+                raster_space,
+                flags,
+            },
+        });
+
+        self.push_item(&item);
+    }
+
+    /// Helper for examples/ code.
+    pub fn push_simple_stacking_context(
+        &mut self,
+        origin: LayoutPoint,
+        spatial_id: di::SpatialId,
+        prim_flags: di::PrimitiveFlags,
+    ) {
+        self.push_simple_stacking_context_with_filters(
+            origin,
+            spatial_id,
+            prim_flags,
+            &[],
+            &[],
+            &[],
+        );
+    }
+
+    /// Helper for examples/ code.
+    pub fn push_simple_stacking_context_with_filters(
+        &mut self,
+        origin: LayoutPoint,
+        spatial_id: di::SpatialId,
+        prim_flags: di::PrimitiveFlags,
+        filters: &[di::FilterOp],
+        filter_datas: &[di::FilterData],
+        filter_primitives: &[di::FilterPrimitive],
+    ) {
+        self.push_stacking_context(
+            origin,
+            spatial_id,
+            prim_flags,
+            None,
+            di::TransformStyle::Flat,
+            di::MixBlendMode::Normal,
+            filters,
+            filter_datas,
+            filter_primitives,
+            di::RasterSpace::Screen,
+            di::StackingContextFlags::empty(),
+        );
+    }
+
+    pub fn pop_stacking_context(&mut self) {
+        self.push_item(&di::DisplayItem::PopStackingContext);
+    }
+
+    pub fn push_stops(&mut self, stops: &[di::GradientStop]) {
+        if stops.is_empty() {
+            return;
+        }
+        self.push_item(&di::DisplayItem::SetGradientStops);
+        self.push_iter(stops);
+    }
+
+    pub fn push_backdrop_filter(
+        &mut self,
+        common: &di::CommonItemProperties,
+        filters: &[di::FilterOp],
+        filter_datas: &[di::FilterData],
+        filter_primitives: &[di::FilterPrimitive],
+    ) {
+        self.push_filters(filters, filter_datas, filter_primitives);
+
+        let item = di::DisplayItem::BackdropFilter(di::BackdropFilterDisplayItem {
+            common: *common,
+        });
+        self.push_item(&item);
+    }
+
+    pub fn push_filters(
+        &mut self,
+        filters: &[di::FilterOp],
+        filter_datas: &[di::FilterData],
+        filter_primitives: &[di::FilterPrimitive],
+    ) {
+        if !filters.is_empty() {
+            self.push_item(&di::DisplayItem::SetFilterOps);
+            self.push_iter(filters);
+        }
+
+        for filter_data in filter_datas {
+            let func_types = [
+                filter_data.func_r_type, filter_data.func_g_type,
+                filter_data.func_b_type, filter_data.func_a_type];
+            self.push_item(&di::DisplayItem::SetFilterData);
+            self.push_iter(&func_types);
+            self.push_iter(&filter_data.r_values);
+            self.push_iter(&filter_data.g_values);
+            self.push_iter(&filter_data.b_values);
+            self.push_iter(&filter_data.a_values);
+        }
+
+        if !filter_primitives.is_empty() {
+            self.push_item(&di::DisplayItem::SetFilterPrimitives);
+            self.push_iter(filter_primitives);
+        }
+    }
+
+    fn generate_clip_index(&mut self) -> di::ClipId {
+        self.next_clip_index += 1;
+        di::ClipId::Clip(self.next_clip_index - 1, self.pipeline_id)
+    }
+
+    fn generate_spatial_index(&mut self) -> di::SpatialId {
+        self.next_spatial_index += 1;
+        di::SpatialId::new(self.next_spatial_index - 1, self.pipeline_id)
+    }
+
+    fn generate_clip_chain_id(&mut self) -> di::ClipChainId {
+        self.next_clip_chain_id += 1;
+        di::ClipChainId(self.next_clip_chain_id - 1, self.pipeline_id)
+    }
+
+    pub fn define_scroll_frame(
+        &mut self,
+        parent_space_and_clip: &di::SpaceAndClipInfo,
+        external_id: di::ExternalScrollId,
+        content_rect: LayoutRect,
+        clip_rect: LayoutRect,
+        scroll_sensitivity: di::ScrollSensitivity,
+        external_scroll_offset: LayoutVector2D,
+    ) -> di::SpaceAndClipInfo {
+        let clip_id = self.generate_clip_index();
+        let scroll_frame_id = self.generate_spatial_index();
+        let item = di::DisplayItem::ScrollFrame(di::ScrollFrameDisplayItem {
+            content_rect,
+            clip_rect,
+            parent_space_and_clip: *parent_space_and_clip,
+            clip_id,
+            scroll_frame_id,
+            external_id,
+            scroll_sensitivity,
+            external_scroll_offset,
+        });
+
+        self.push_item(&item);
+
+        di::SpaceAndClipInfo {
+            spatial_id: scroll_frame_id,
+            clip_id,
+        }
+    }
+
+    pub fn define_clip_chain<I>(
+        &mut self,
+        parent: Option<di::ClipChainId>,
+        clips: I,
+    ) -> di::ClipChainId
+    where
+        I: IntoIterator<Item = di::ClipId>,
+        I::IntoIter: ExactSizeIterator + Clone,
+    {
+        let id = self.generate_clip_chain_id();
+        self.push_item(&di::DisplayItem::ClipChain(di::ClipChainItem { id, parent }));
+        self.push_iter(clips);
+        id
+    }
+
+    pub fn define_clip_image_mask(
+        &mut self,
+        parent_space_and_clip: &di::SpaceAndClipInfo,
+        image_mask: di::ImageMask,
+    ) -> di::ClipId {
+        let id = self.generate_clip_index();
+        let item = di::DisplayItem::ImageMaskClip(di::ImageMaskClipDisplayItem {
+            id,
+            parent_space_and_clip: *parent_space_and_clip,
+            image_mask,
+        });
+
+        self.push_item(&item);
+        id
+    }
+
+    pub fn define_clip_rect(
+        &mut self,
+        parent_space_and_clip: &di::SpaceAndClipInfo,
+        clip_rect: LayoutRect,
+    ) -> di::ClipId {
+        let id = self.generate_clip_index();
+        let item = di::DisplayItem::RectClip(di::RectClipDisplayItem {
+            id,
+            parent_space_and_clip: *parent_space_and_clip,
+            clip_rect,
+        });
+
+        self.push_item(&item);
+        id
+    }
+
+    pub fn define_clip_rounded_rect(
+        &mut self,
+        parent_space_and_clip: &di::SpaceAndClipInfo,
+        clip: di::ComplexClipRegion,
+    ) -> di::ClipId {
+        let id = self.generate_clip_index();
+        let item = di::DisplayItem::RoundedRectClip(di::RoundedRectClipDisplayItem {
+            id,
+            parent_space_and_clip: *parent_space_and_clip,
+            clip,
+        });
+
+        self.push_item(&item);
+        id
+    }
+
+    pub fn define_clip<I>(
+        &mut self,
+        parent_space_and_clip: &di::SpaceAndClipInfo,
+        clip_rect: LayoutRect,
+        complex_clips: I,
+    ) -> di::ClipId
+    where
+        I: IntoIterator<Item = di::ComplexClipRegion>,
+        I::IntoIter: ExactSizeIterator + Clone,
+    {
+        let id = self.generate_clip_index();
+        let item = di::DisplayItem::Clip(di::ClipDisplayItem {
+            id,
+            parent_space_and_clip: *parent_space_and_clip,
+            clip_rect,
+        });
+
+        self.push_item(&item);
+        self.push_iter(complex_clips);
+        id
+    }
+
+    pub fn define_sticky_frame(
+        &mut self,
+        parent_spatial_id: di::SpatialId,
+        frame_rect: LayoutRect,
+        margins: SideOffsets2D<Option<f32>, LayoutPixel>,
+        vertical_offset_bounds: di::StickyOffsetBounds,
+        horizontal_offset_bounds: di::StickyOffsetBounds,
+        previously_applied_offset: LayoutVector2D,
+    ) -> di::SpatialId {
+        let id = self.generate_spatial_index();
+        let item = di::DisplayItem::StickyFrame(di::StickyFrameDisplayItem {
+            parent_spatial_id,
+            id,
+            bounds: frame_rect,
+            margins,
+            vertical_offset_bounds,
+            horizontal_offset_bounds,
+            previously_applied_offset,
+        });
+
+        self.push_item(&item);
+        id
+    }
+
+    pub fn push_iframe(
+        &mut self,
+        bounds: LayoutRect,
+        clip_rect: LayoutRect,
+        space_and_clip: &di::SpaceAndClipInfo,
+        pipeline_id: PipelineId,
+        ignore_missing_pipeline: bool
+    ) {
+        let item = di::DisplayItem::Iframe(di::IframeDisplayItem {
+            bounds,
+            clip_rect,
+            space_and_clip: *space_and_clip,
+            pipeline_id,
+            ignore_missing_pipeline,
+        });
+        self.push_item(&item);
+    }
+
+    pub fn push_shadow(
+        &mut self,
+        space_and_clip: &di::SpaceAndClipInfo,
+        shadow: di::Shadow,
+        should_inflate: bool,
+    ) {
+        let item = di::DisplayItem::PushShadow(di::PushShadowDisplayItem {
+            space_and_clip: *space_and_clip,
+            shadow,
+            should_inflate,
+        });
+        self.push_item(&item);
+    }
+
+    pub fn pop_all_shadows(&mut self) {
+        self.push_item(&di::DisplayItem::PopAllShadows);
+    }
+
+    pub fn start_item_group(&mut self) {
+        debug_assert!(!self.writing_to_chunk);
+        debug_assert!(self.pending_chunk.is_empty());
+
+        self.writing_to_chunk = true;
+    }
+
+    fn flush_pending_item_group(&mut self, key: di::ItemKey) {
+        // Push RetainedItems-marker to extra_data section.
+        self.push_retained_items(key);
+
+        // Push pending chunk to extra_data section.
+        self.extra_data.append(&mut self.pending_chunk);
+
+        // Push ReuseItems-marker to data section.
+        self.push_reuse_items(key);
+    }
+
+    pub fn finish_item_group(&mut self, key: di::ItemKey) -> bool {
+        debug_assert!(self.writing_to_chunk);
+        self.writing_to_chunk = false;
+
+        if self.pending_chunk.is_empty() {
+            return false;
+        }
+
+        self.flush_pending_item_group(key);
+        true
+    }
+
+    pub fn cancel_item_group(&mut self, discard: bool) {
+        debug_assert!(self.writing_to_chunk);
+        self.writing_to_chunk = false;
+
+        if discard {
+            self.pending_chunk.clear();
+        } else {
+            // Push pending chunk to data section.
+            self.data.append(&mut self.pending_chunk);
+        }
+    }
+
+    pub fn push_reuse_items(&mut self, key: di::ItemKey) {
+        self.push_item_to_section(
+            &di::DisplayItem::ReuseItems(key),
+            DisplayListSection::Data
+        );
+    }
+
+    fn push_retained_items(&mut self, key: di::ItemKey) {
+        self.push_item_to_section(
+            &di::DisplayItem::RetainedItems(key),
+            DisplayListSection::ExtraData
+        );
+    }
+
+    pub fn set_cache_size(&mut self, cache_size: usize) {
+        self.cache_size = cache_size;
+    }
+
+    pub fn finalize(mut self) -> (PipelineId, BuiltDisplayList) {
+        assert!(self.save_state.is_none(), "Finalized DisplayListBuilder with a pending save");
+
+        if let Some(content) = self.serialized_content_buffer.take() {
+            println!("-- WebRender display list for {:?} --\n{}",
+                self.pipeline_id, content);
+        }
+
+        // Add `DisplayItem::max_size` zone of zeroes to the end of display list
+        // so there is at least this amount available in the display list during
+        // serialization.
+        ensure_red_zone::<di::DisplayItem>(&mut self.data);
+
+        let extra_data_offset = self.data.len();
+
+        if self.extra_data.len() > 0 {
+            ensure_red_zone::<di::DisplayItem>(&mut self.extra_data);
+            self.data.extend(self.extra_data);
+        }
+
+        let end_time = precise_time_ns();
+        (
+            self.pipeline_id,
+            BuiltDisplayList {
+                descriptor: BuiltDisplayListDescriptor {
+                    builder_start_time: self.builder_start_time,
+                    builder_finish_time: end_time,
+                    send_start_time: end_time,
+                    total_clip_nodes: self.next_clip_index,
+                    total_spatial_nodes: self.next_spatial_index,
+                    cache_size: self.cache_size,
+                    extra_data_offset,
+                },
+                data: self.data,
+            },
+        )
+    }
+}
diff --git a/gfx/wr/webrender_api/src/font.rs b/gfx/wr/webrender_api/src/font.rs
new file mode 100644
index 0000000000..3052db8f9e
--- /dev/null
+++ b/gfx/wr/webrender_api/src/font.rs
@@ -0,0 +1,605 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#[cfg(target_os = "macos")]
+use core_foundation::string::CFString;
+#[cfg(target_os = "macos")]
+use core_graphics::font::CGFont;
+use peek_poke::PeekPoke;
+#[cfg(target_os = "macos")]
+use serde::de::{self, Deserialize, Deserializer};
+#[cfg(target_os = "macos")]
+use serde::ser::{Serialize, Serializer};
+use std::cmp::Ordering;
+use std::hash::{Hash, Hasher};
+#[cfg(not(target_os = "macos"))]
+use std::path::PathBuf;
+use std::sync::{Arc, RwLock, RwLockReadGuard};
+use std::collections::HashMap;
+// local imports
+use crate::IdNamespace;
+use crate::channel::Sender;
+use crate::color::ColorU;
+use crate::units::LayoutPoint;
+
+/// Hashable floating-point storage for font size.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, PartialOrd, Deserialize, Serialize)]
+pub struct FontSize(pub f32);
+
+impl Ord for FontSize {
+    fn cmp(&self, other: &FontSize) -> Ordering {
+        self.partial_cmp(other).unwrap_or(Ordering::Equal)
+    }
+}
+
+impl Eq for FontSize {}
+
+impl Hash for FontSize {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.0.to_bits().hash(state);
+    }
+}
+
+impl From<f32> for FontSize {
+    fn from(size: f32) -> Self { FontSize(size) }
+}
+
+impl From<FontSize> for f32 {
+    fn from(size: FontSize) -> Self { size.0 }
+}
+
+impl FontSize {
+    pub fn zero() -> Self { FontSize(0.0) }
+
+    pub fn from_f32_px(size: f32) -> Self { FontSize(size) }
+
+    pub fn to_f32_px(&self) -> f32 { self.0 }
+
+    pub fn from_f64_px(size: f64) -> Self { FontSize(size as f32) }
+
+    pub fn to_f64_px(&self) -> f64 { self.0 as f64 }
+}
+
+/// Immutable description of a font instance requested by the user of the API.
+///
+/// `BaseFontInstance` can be identified by a `FontInstanceKey` so we should
+/// never need to hash it.
+#[derive(Clone, PartialEq, Eq, Debug, Ord, PartialOrd, MallocSizeOf)]
+#[cfg_attr(feature = "serialize", derive(Serialize))]
+#[cfg_attr(feature = "deserialize", derive(Deserialize))]
+pub struct BaseFontInstance {
+    ///
+    pub instance_key: FontInstanceKey,
+    ///
+    pub font_key: FontKey,
+    ///
+    pub size: FontSize,
+    ///
+    pub bg_color: ColorU,
+    ///
+    pub render_mode: FontRenderMode,
+    ///
+    pub flags: FontInstanceFlags,
+    ///
+    pub synthetic_italics: SyntheticItalics,
+    ///
+    #[cfg_attr(any(feature = "serialize", feature = "deserialize"), serde(skip))]
+    pub platform_options: Option<FontInstancePlatformOptions>,
+    ///
+    pub variations: Vec<FontVariation>,
+}
+
+pub type FontInstanceMap = HashMap<FontInstanceKey, Arc<BaseFontInstance>>;
+/// A map of font instance data accessed concurrently from multiple threads.
+#[derive(Clone)]
+#[cfg_attr(feature = "serialize", derive(Serialize))]
+#[cfg_attr(feature = "deserialize", derive(Deserialize))]
+pub struct SharedFontInstanceMap {
+    map: Arc<RwLock<FontInstanceMap>>,
+}
+
+impl SharedFontInstanceMap {
+    /// Creates an empty shared map.
+    pub fn new() -> Self {
+        SharedFontInstanceMap {
+            map: Arc::new(RwLock::new(HashMap::default()))
+        }
+    }
+
+    /// Acquires a write lock on the shared map.
+    pub fn lock(&mut self) -> Option<RwLockReadGuard<FontInstanceMap>> {
+        self.map.read().ok()
+    }
+
+    ///
+    pub fn get_font_instance_data(&self, key: FontInstanceKey) -> Option<FontInstanceData> {
+        match self.map.read().unwrap().get(&key) {
+            Some(instance) => Some(FontInstanceData {
+                font_key: instance.font_key,
+                size: instance.size.into(),
+                options: Some(FontInstanceOptions {
+                  render_mode: instance.render_mode,
+                  flags: instance.flags,
+                  bg_color: instance.bg_color,
+                  synthetic_italics: instance.synthetic_italics,
+                }),
+                platform_options: instance.platform_options,
+                variations: instance.variations.clone(),
+            }),
+            None => None,
+        }
+    }
+
+    /// Replace the shared map with the provided map.
+    pub fn set(&mut self, map: FontInstanceMap) {
+        *self.map.write().unwrap() = map;
+    }
+
+    ///
+    pub fn get_font_instance(&self, instance_key: FontInstanceKey) -> Option<Arc<BaseFontInstance>> {
+        let instance_map = self.map.read().unwrap();
+        instance_map.get(&instance_key).map(|instance| { Arc::clone(instance) })
+    }
+
+    ///
+    pub fn add_font_instance(
+        &mut self,
+        instance_key: FontInstanceKey,
+        font_key: FontKey,
+        size: f32,
+        options: Option<FontInstanceOptions>,
+        platform_options: Option<FontInstancePlatformOptions>,
+        variations: Vec<FontVariation>,
+    ) {
+        let FontInstanceOptions {
+            render_mode,
+            flags,
+            bg_color,
+            synthetic_italics,
+            ..
+        } = options.unwrap_or_default();
+
+        let instance = Arc::new(BaseFontInstance {
+            instance_key,
+            font_key,
+            size: size.into(),
+            bg_color,
+            render_mode,
+            flags,
+            synthetic_italics,
+            platform_options,
+            variations,
+        });
+
+        self.map
+            .write()
+            .unwrap()
+            .insert(instance_key, instance);
+    }
+
+    ///
+    pub fn delete_font_instance(&mut self, instance_key: FontInstanceKey) {
+        self.map.write().unwrap().remove(&instance_key);
+    }
+
+    ///
+    pub fn clear_namespace(&mut self, namespace: IdNamespace) {
+        self.map
+            .write()
+            .unwrap()
+            .retain(|key, _| key.0 != namespace);
+    }
+
+    ///
+    pub fn clone_map(&self) -> FontInstanceMap {
+        self.map.read().unwrap().clone()
+    }
+}
+
+#[cfg(not(target_os = "macos"))]
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct NativeFontHandle {
+    pub path: PathBuf,
+    pub index: u32,
+}
+
+#[cfg(target_os = "macos")]
+#[derive(Clone)]
+pub struct NativeFontHandle(pub CGFont);
+
+#[cfg(target_os = "macos")]
+impl Serialize for NativeFontHandle {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        self.0
+            .postscript_name()
+            .to_string()
+            .serialize(serializer)
+    }
+}
+
+#[cfg(target_os = "macos")]
+impl<'de> Deserialize<'de> for NativeFontHandle {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let postscript_name: String = Deserialize::deserialize(deserializer)?;
+
+        match CGFont::from_name(&CFString::new(&*postscript_name)) {
+            Ok(font) => Ok(NativeFontHandle(font)),
+            Err(_) => Err(de::Error::custom(
+                "Couldn't find a font with that PostScript name!",
+            )),
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Copy, Clone, Deserialize, Serialize, Debug)]
+pub struct GlyphDimensions {
+    pub left: i32,
+    pub top: i32,
+    pub width: i32,
+    pub height: i32,
+    pub advance: f32,
+}
+
+pub struct GlyphDimensionRequest {
+    pub key: FontInstanceKey,
+    pub glyph_indices: Vec<GlyphIndex>,
+    pub sender: Sender<Vec<Option<GlyphDimensions>>>,
+}
+
+pub struct GlyphIndexRequest {
+    pub key: FontKey,
+    pub text: String,
+    pub sender: Sender<Vec<Option<u32>>>,
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, Ord, PartialOrd)]
+pub struct FontKey(pub IdNamespace, pub u32);
+
+impl FontKey {
+    pub fn new(namespace: IdNamespace, key: u32) -> FontKey {
+        FontKey(namespace, key)
+    }
+}
+
+/// Container for the raw data describing a font. This might be a stream of
+/// bytes corresponding to a downloaded font, or a handle to a native font from
+/// the operating system.
+///
+/// Note that fonts need to be instantiated before being used, which involves
+/// assigning size and various other options. The word 'template' here is
+/// intended to distinguish this data from instance-specific data.
+#[derive(Clone)]
+pub enum FontTemplate {
+    Raw(Arc<Vec<u8>>, u32),
+    Native(NativeFontHandle),
+}
+
+#[repr(u8)]
+#[derive(Debug, Copy, Clone, Hash, Eq, MallocSizeOf, PartialEq, Serialize, Deserialize, Ord, PartialOrd, PeekPoke)]
+pub enum FontRenderMode {
+    Mono = 0,
+    Alpha,
+    Subpixel,
+}
+
+impl Default for FontRenderMode {
+    fn default() -> Self {
+        FontRenderMode::Mono
+    }
+}
+
+impl FontRenderMode {
+    // Combine two font render modes such that the lesser amount of AA limits the AA of the result.
+    pub fn limit_by(self, other: FontRenderMode) -> FontRenderMode {
+        match (self, other) {
+            (FontRenderMode::Subpixel, _) | (_, FontRenderMode::Mono) => other,
+            _ => self,
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialOrd, Deserialize, Serialize)]
+pub struct FontVariation {
+    pub tag: u32,
+    pub value: f32,
+}
+
+impl Ord for FontVariation {
+    fn cmp(&self, other: &FontVariation) -> Ordering {
+        self.tag.cmp(&other.tag)
+            .then(self.value.to_bits().cmp(&other.value.to_bits()))
+    }
+}
+
+impl PartialEq for FontVariation {
+    fn eq(&self, other: &FontVariation) -> bool {
+        self.tag == other.tag &&
+        self.value.to_bits() == other.value.to_bits()
+    }
+}
+
+impl Eq for FontVariation {}
+
+impl Hash for FontVariation {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.tag.hash(state);
+        self.value.to_bits().hash(state);
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Hash, Eq, PartialEq, PartialOrd, Ord, Serialize, PeekPoke)]
+pub struct GlyphOptions {
+    pub render_mode: FontRenderMode,
+    pub flags: FontInstanceFlags,
+}
+
+impl Default for GlyphOptions {
+    fn default() -> Self {
+        GlyphOptions {
+            render_mode: FontRenderMode::Subpixel,
+            flags: FontInstanceFlags::empty(),
+        }
+    }
+}
+
+bitflags! {
+    #[repr(C)]
+    #[derive(Deserialize, MallocSizeOf, Serialize, PeekPoke)]
+    pub struct FontInstanceFlags: u32 {
+        // Common flags
+        const SYNTHETIC_BOLD    = 1 << 1;
+        const EMBEDDED_BITMAPS  = 1 << 2;
+        const SUBPIXEL_BGR      = 1 << 3;
+        const TRANSPOSE         = 1 << 4;
+        const FLIP_X            = 1 << 5;
+        const FLIP_Y            = 1 << 6;
+        const SUBPIXEL_POSITION = 1 << 7;
+        const VERTICAL          = 1 << 8;
+
+        // Internal flags
+        const TRANSFORM_GLYPHS  = 1 << 12;
+        const TEXTURE_PADDING   = 1 << 13;
+
+        // Windows flags
+        const FORCE_GDI         = 1 << 16;
+        const FORCE_SYMMETRIC   = 1 << 17;
+        const NO_SYMMETRIC      = 1 << 18;
+
+        // Mac flags
+        const FONT_SMOOTHING    = 1 << 16;
+
+        // FreeType flags
+        const FORCE_AUTOHINT    = 1 << 16;
+        const NO_AUTOHINT       = 1 << 17;
+        const VERTICAL_LAYOUT   = 1 << 18;
+        const LCD_VERTICAL      = 1 << 19;
+    }
+}
+
+impl Default for FontInstanceFlags {
+    #[cfg(target_os = "windows")]
+    fn default() -> FontInstanceFlags {
+        FontInstanceFlags::SUBPIXEL_POSITION
+    }
+
+    #[cfg(target_os = "macos")]
+    fn default() -> FontInstanceFlags {
+        FontInstanceFlags::SUBPIXEL_POSITION |
+        FontInstanceFlags::FONT_SMOOTHING
+    }
+
+    #[cfg(not(any(target_os = "macos", target_os = "windows")))]
+    fn default() -> FontInstanceFlags {
+        FontInstanceFlags::SUBPIXEL_POSITION
+    }
+}
+
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Hash, Eq, MallocSizeOf, PartialEq, PartialOrd, Ord, Serialize)]
+pub struct SyntheticItalics {
+    // Angle in degrees (-90..90) for synthetic italics in 8.8 fixed-point.
+    pub angle: i16,
+}
+
+impl SyntheticItalics {
+    pub const ANGLE_SCALE: f32 = 256.0;
+
+    pub fn from_degrees(degrees: f32) -> Self {
+        SyntheticItalics { angle: (degrees.max(-89.0).min(89.0) * Self::ANGLE_SCALE) as i16 }
+    }
+
+    pub fn to_degrees(self) -> f32 {
+        self.angle as f32 / Self::ANGLE_SCALE
+    }
+
+    pub fn to_radians(self) -> f32 {
+        self.to_degrees().to_radians()
+    }
+
+    pub fn to_skew(self) -> f32 {
+        self.to_radians().tan()
+    }
+
+    pub fn enabled() -> Self {
+        Self::from_degrees(14.0)
+    }
+
+    pub fn disabled() -> Self {
+        SyntheticItalics { angle: 0 }
+    }
+
+    pub fn is_enabled(self) -> bool {
+        self.angle != 0
+    }
+}
+
+impl Default for SyntheticItalics {
+    fn default() -> Self {
+        SyntheticItalics::disabled()
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Hash, Eq, PartialEq, PartialOrd, Ord, Serialize)]
+pub struct FontInstanceOptions {
+    pub render_mode: FontRenderMode,
+    pub flags: FontInstanceFlags,
+    /// When bg_color.a is != 0 and render_mode is FontRenderMode::Subpixel,
+    /// the text will be rendered with bg_color.r/g/b as an opaque estimated
+    /// background color.
+    pub bg_color: ColorU,
+    pub synthetic_italics: SyntheticItalics,
+}
+
+impl Default for FontInstanceOptions {
+    fn default() -> FontInstanceOptions {
+        FontInstanceOptions {
+            render_mode: FontRenderMode::Subpixel,
+            flags: Default::default(),
+            bg_color: ColorU::new(0, 0, 0, 0),
+            synthetic_italics: SyntheticItalics::disabled(),
+        }
+    }
+}
+
+#[cfg(target_os = "windows")]
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Hash, Eq, MallocSizeOf, PartialEq, PartialOrd, Ord, Serialize)]
+pub struct FontInstancePlatformOptions {
+    pub gamma: u16, // percent
+    pub contrast: u8, // percent
+    pub cleartype_level: u8, // percent
+}
+
+#[cfg(target_os = "windows")]
+impl Default for FontInstancePlatformOptions {
+    fn default() -> FontInstancePlatformOptions {
+        FontInstancePlatformOptions {
+            gamma: 180, // Default DWrite gamma
+            contrast: 100,
+            cleartype_level: 100,
+        }
+    }
+}
+
+#[cfg(target_os = "macos")]
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Hash, Eq, MallocSizeOf, PartialEq, PartialOrd, Ord, Serialize)]
+pub struct FontInstancePlatformOptions {
+    pub unused: u32,
+}
+
+#[cfg(target_os = "macos")]
+impl Default for FontInstancePlatformOptions {
+    fn default() -> FontInstancePlatformOptions {
+        FontInstancePlatformOptions {
+            unused: 0,
+        }
+    }
+}
+
+#[cfg(not(any(target_os = "macos", target_os = "windows")))]
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, PartialOrd, Ord, Serialize)]
+pub enum FontLCDFilter {
+    None,
+    Default,
+    Light,
+    Legacy,
+}
+
+#[cfg(not(any(target_os = "macos", target_os = "windows")))]
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, PartialOrd, Ord, Serialize)]
+pub enum FontHinting {
+    None,
+    Mono,
+    Light,
+    Normal,
+    LCD,
+}
+
+#[cfg(not(any(target_os = "macos", target_os = "windows")))]
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Hash, Eq, MallocSizeOf, PartialEq, PartialOrd, Ord, Serialize)]
+pub struct FontInstancePlatformOptions {
+    pub lcd_filter: FontLCDFilter,
+    pub hinting: FontHinting,
+}
+
+#[cfg(not(any(target_os = "macos", target_os = "windows")))]
+impl Default for FontInstancePlatformOptions {
+    fn default() -> FontInstancePlatformOptions {
+        FontInstancePlatformOptions {
+            lcd_filter: FontLCDFilter::Default,
+            hinting: FontHinting::LCD,
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq, Ord, PartialOrd, MallocSizeOf, PeekPoke)]
+#[derive(Deserialize, Serialize)]
+pub struct FontInstanceKey(pub IdNamespace, pub u32);
+
+impl FontInstanceKey {
+    pub fn new(namespace: IdNamespace, key: u32) -> FontInstanceKey {
+        FontInstanceKey(namespace, key)
+    }
+}
+
+/// Data corresponding to an instantiation of a font, with size and
+/// other options specified.
+///
+/// Note that the actual font is stored out-of-band in `FontTemplate`.
+#[derive(Clone)]
+pub struct FontInstanceData {
+    pub font_key: FontKey,
+    pub size: f32,
+    pub options: Option<FontInstanceOptions>,
+    pub platform_options: Option<FontInstancePlatformOptions>,
+    pub variations: Vec<FontVariation>,
+}
+
+pub type GlyphIndex = u32;
+
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct GlyphInstance {
+    pub index: GlyphIndex,
+    pub point: LayoutPoint,
+}
+
+impl Default for GlyphInstance {
+    fn default() -> Self {
+        GlyphInstance {
+            index: 0,
+            point: LayoutPoint::zero(),
+        }
+    }
+}
+
+impl Eq for GlyphInstance {}
+
+#[cfg_attr(feature = "cargo-clippy", allow(clippy::derive_hash_xor_eq))]
+impl Hash for GlyphInstance {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        // Note: this is inconsistent with the Eq impl for -0.0 (don't care).
+        self.index.hash(state);
+        self.point.x.to_bits().hash(state);
+        self.point.y.to_bits().hash(state);
+    }
+}
diff --git a/gfx/wr/webrender_api/src/gradient_builder.rs b/gfx/wr/webrender_api/src/gradient_builder.rs
new file mode 100644
index 0000000000..883acbafa3
--- /dev/null
+++ b/gfx/wr/webrender_api/src/gradient_builder.rs
@@ -0,0 +1,178 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::display_item as di;
+use crate::units::*;
+
+
+/// Construct a gradient to be used in display lists.
+///
+/// Each gradient needs at least two stops.
+pub struct GradientBuilder {
+    stops: Vec<di::GradientStop>,
+}
+
+impl GradientBuilder {
+    /// Create a new gradient builder.
+    pub fn new() -> Self {
+        GradientBuilder {
+            stops: Vec::new(),
+        }
+    }
+
+    /// Create a gradient builder with a list of stops.
+    pub fn with_stops(stops: Vec<di::GradientStop>) -> GradientBuilder {
+        GradientBuilder { stops }
+    }
+
+    /// Push an additional stop for the gradient.
+    pub fn push(&mut self, stop: di::GradientStop) {
+        self.stops.push(stop);
+    }
+
+    /// Get a reference to the list of stops.
+    pub fn stops(&self) -> &[di::GradientStop] {
+        self.stops.as_ref()
+    }
+
+    /// Return the gradient stops vector.
+    pub fn into_stops(self) -> Vec<di::GradientStop> {
+        self.stops
+    }
+
+    /// Produce a linear gradient, normalize the stops.
+    pub fn gradient(
+        &mut self,
+        start_point: LayoutPoint,
+        end_point: LayoutPoint,
+        extend_mode: di::ExtendMode,
+    ) -> di::Gradient {
+        let (start_offset, end_offset) = self.normalize(extend_mode);
+        let start_to_end = end_point - start_point;
+
+        di::Gradient {
+            start_point: start_point + start_to_end * start_offset,
+            end_point: start_point + start_to_end * end_offset,
+            extend_mode,
+        }
+    }
+
+    /// Produce a radial gradient, normalize the stops.
+    ///
+    /// Will replace the gradient with a single color
+    /// if the radius negative.
+    pub fn radial_gradient(
+        &mut self,
+        center: LayoutPoint,
+        radius: LayoutSize,
+        extend_mode: di::ExtendMode,
+    ) -> di::RadialGradient {
+        if radius.width <= 0.0 || radius.height <= 0.0 {
+            // The shader cannot handle a non positive radius. So
+            // reuse the stops vector and construct an equivalent
+            // gradient.
+            let last_color = self.stops.last().unwrap().color;
+
+            self.stops.clear();
+            self.stops.push(di::GradientStop { offset: 0.0, color: last_color, });
+            self.stops.push(di::GradientStop { offset: 1.0, color: last_color, });
+
+            return di::RadialGradient {
+                center,
+                radius: LayoutSize::new(1.0, 1.0),
+                start_offset: 0.0,
+                end_offset: 1.0,
+                extend_mode,
+            };
+        }
+
+        let (start_offset, end_offset) =
+            self.normalize(extend_mode);
+
+        di::RadialGradient {
+            center,
+            radius,
+            start_offset,
+            end_offset,
+            extend_mode,
+        }
+    }
+
+    /// Produce a conic gradient, normalize the stops.
+    pub fn conic_gradient(
+        &mut self,
+        center: LayoutPoint,
+        angle: f32,
+        extend_mode: di::ExtendMode,
+    ) -> di::ConicGradient {
+        let (start_offset, end_offset) =
+            self.normalize(extend_mode);
+
+        di::ConicGradient {
+            center,
+            angle,
+            start_offset,
+            end_offset,
+            extend_mode,
+        }
+    }
+
+    /// Gradients can be defined with stops outside the range of [0, 1]
+    /// when this happens the gradient needs to be normalized by adjusting
+    /// the gradient stops and gradient line into an equivalent gradient
+    /// with stops in the range [0, 1]. this is done by moving the beginning
+    /// of the gradient line to where stop[0] and the end of the gradient line
+    /// to stop[n-1]. this function adjusts the stops in place, and returns
+    /// the amount to adjust the gradient line start and stop.
+    fn normalize(&mut self, extend_mode: di::ExtendMode) -> (f32, f32) {
+        let stops = &mut self.stops;
+        assert!(stops.len() >= 2);
+
+        let first = *stops.first().unwrap();
+        let last = *stops.last().unwrap();
+
+        assert!(first.offset <= last.offset);
+
+        let stops_delta = last.offset - first.offset;
+
+        if stops_delta > 0.000001 {
+            for stop in stops {
+                stop.offset = (stop.offset - first.offset) / stops_delta;
+            }
+
+            (first.offset, last.offset)
+        } else {
+            // We have a degenerate gradient and can't accurately transform the stops
+            // what happens here depends on the repeat behavior, but in any case
+            // we reconstruct the gradient stops to something simpler and equivalent
+            stops.clear();
+
+            match extend_mode {
+                di::ExtendMode::Clamp => {
+                    // This gradient is two colors split at the offset of the stops,
+                    // so create a gradient with two colors split at 0.5 and adjust
+                    // the gradient line so 0.5 is at the offset of the stops
+                    stops.push(di::GradientStop { color: first.color, offset: 0.0, });
+                    stops.push(di::GradientStop { color: first.color, offset: 0.5, });
+                    stops.push(di::GradientStop { color: last.color, offset: 0.5, });
+                    stops.push(di::GradientStop { color: last.color, offset: 1.0, });
+
+                    let offset = last.offset;
+
+                    (offset - 0.5, offset + 0.5)
+                }
+                di::ExtendMode::Repeat => {
+                    // A repeating gradient with stops that are all in the same
+                    // position should just display the last color. I believe the
+                    // spec says that it should be the average color of the gradient,
+                    // but this matches what Gecko and Blink does
+                    stops.push(di::GradientStop { color: last.color, offset: 0.0, });
+                    stops.push(di::GradientStop { color: last.color, offset: 1.0, });
+
+                    (0.0, 1.0)
+                }
+            }
+        }
+    }
+}
diff --git a/gfx/wr/webrender_api/src/image.rs b/gfx/wr/webrender_api/src/image.rs
new file mode 100644
index 0000000000..76e592ddaf
--- /dev/null
+++ b/gfx/wr/webrender_api/src/image.rs
@@ -0,0 +1,585 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![deny(missing_docs)]
+
+use euclid::{size2, Rect, num::Zero};
+use peek_poke::PeekPoke;
+use std::ops::{Add, Sub};
+use std::sync::Arc;
+// local imports
+use crate::{IdNamespace, TileSize};
+use crate::display_item::ImageRendering;
+use crate::font::{FontInstanceKey, FontInstanceData, FontKey, FontTemplate};
+use crate::units::*;
+
+/// The default tile size for blob images and regular images larger than
+/// the maximum texture size.
+pub const DEFAULT_TILE_SIZE: TileSize = 512;
+
+/// An opaque identifier describing an image registered with WebRender.
+/// This is used as a handle to reference images, and is used as the
+/// hash map key for the actual image storage in the `ResourceCache`.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct ImageKey(pub IdNamespace, pub u32);
+
+impl Default for ImageKey {
+    fn default() -> Self {
+        ImageKey::DUMMY
+    }
+}
+
+impl ImageKey {
+    /// Placeholder Image key, used to represent None.
+    pub const DUMMY: Self = ImageKey(IdNamespace(0), 0);
+
+    /// Mints a new ImageKey. The given ID must be unique.
+    pub fn new(namespace: IdNamespace, key: u32) -> Self {
+        ImageKey(namespace, key)
+    }
+}
+
+/// An opaque identifier describing a blob image registered with WebRender.
+/// This is used as a handle to reference blob images, and can be used as an
+/// image in display items.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, PartialEq, Serialize)]
+pub struct BlobImageKey(pub ImageKey);
+
+impl BlobImageKey {
+    /// Interpret this blob image as an image for a display item.
+    pub fn as_image(self) -> ImageKey {
+        self.0
+    }
+}
+
+/// An arbitrary identifier for an external image provided by the
+/// application. It must be a unique identifier for each external
+/// image.
+#[repr(C)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, Serialize, Deserialize)]
+pub struct ExternalImageId(pub u64);
+
+/// The source for an external image.
+pub enum ExternalImageSource<'a> {
+    /// A raw pixel buffer.
+    RawData(&'a [u8]),
+    /// A gl::GLuint texture handle.
+    NativeTexture(u32),
+    /// An invalid source.
+    Invalid,
+}
+
+/// The data that an external client should provide about
+/// an external image. For instance, if providing video frames,
+/// the application could call wr.render() whenever a new
+/// video frame is ready. Note that the UV coords are supplied
+/// in texel-space!
+pub struct ExternalImage<'a> {
+    /// UV coordinates for the image.
+    pub uv: TexelRect,
+    /// The source for this image's contents.
+    pub source: ExternalImageSource<'a>,
+}
+
+/// The interfaces that an application can implement to support providing
+/// external image buffers.
+/// When the application passes an external image to WR, it should keep that
+/// external image life time. People could check the epoch id in RenderNotifier
+/// at the client side to make sure that the external image is not used by WR.
+/// Then, do the clean up for that external image.
+pub trait ExternalImageHandler {
+    /// Lock the external image. Then, WR could start to read the image content.
+    /// The WR client should not change the image content until the unlock()
+    /// call. Provide ImageRendering for NativeTexture external images.
+    fn lock(&mut self, key: ExternalImageId, channel_index: u8, rendering: ImageRendering) -> ExternalImage;
+    /// Unlock the external image. WR should not read the image content
+    /// after this call.
+    fn unlock(&mut self, key: ExternalImageId, channel_index: u8);
+}
+
+/// Specifies the type of texture target in driver terms.
+#[repr(u8)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
+pub enum ImageBufferKind {
+    /// Standard texture. This maps to GL_TEXTURE_2D in OpenGL.
+    Texture2D = 0,
+    /// Rectangle texture. This maps to GL_TEXTURE_RECTANGLE in OpenGL. This
+    /// is similar to a standard texture, with a few subtle differences
+    /// (no mipmaps, non-power-of-two dimensions, different coordinate space)
+    /// that make it useful for representing the kinds of textures we use
+    /// in WebRender. See https://www.khronos.org/opengl/wiki/Rectangle_Texture
+    /// for background on Rectangle textures.
+    TextureRect = 1,
+    /// External texture. This maps to GL_TEXTURE_EXTERNAL_OES in OpenGL, which
+    /// is an extension. This is used for image formats that OpenGL doesn't
+    /// understand, particularly YUV. See
+    /// https://www.khronos.org/registry/OpenGL/extensions/OES/OES_EGL_image_external.txt
+    TextureExternal = 2,
+    /// Array texture. This maps to GL_TEXTURE_2D_ARRAY in OpenGL. See
+    /// https://www.khronos.org/opengl/wiki/Array_Texture for background
+    /// on Array textures.
+    Texture2DArray = 3,
+}
+
+/// Storage format identifier for externally-managed images.
+#[repr(u8)]
+#[derive(Debug, Copy, Clone, Eq, Hash, PartialEq, Serialize, Deserialize)]
+pub enum ExternalImageType {
+    /// The image is texture-backed.
+    TextureHandle(ImageBufferKind),
+    /// The image is heap-allocated by the embedding.
+    Buffer,
+}
+
+/// Descriptor for external image resources. See `ImageData`.
+#[repr(C)]
+#[derive(Debug, Copy, Clone, Eq, Hash, PartialEq, Serialize, Deserialize)]
+pub struct ExternalImageData {
+    /// The identifier of this external image, provided by the embedding.
+    pub id: ExternalImageId,
+    /// For multi-plane images (i.e. YUV), indicates the plane of the
+    /// original image that this struct represents. 0 for single-plane images.
+    pub channel_index: u8,
+    /// Storage format identifier.
+    pub image_type: ExternalImageType,
+}
+
+/// Specifies the format of a series of pixels, in driver terms.
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, PartialEq, Serialize)]
+pub enum ImageFormat {
+    /// One-channel, byte storage. The "red" doesn't map to the color
+    /// red per se, and is just the way that OpenGL has historically referred
+    /// to single-channel buffers.
+    R8 = 1,
+    /// One-channel, short storage
+    R16 = 2,
+    /// Four channels, byte storage.
+    BGRA8 = 3,
+    /// Four channels, float storage.
+    RGBAF32 = 4,
+    /// Two-channels, byte storage. Similar to `R8`, this just means
+    /// "two channels" rather than "red and green".
+    RG8 = 5,
+    /// Two-channels, byte storage. Similar to `R16`, this just means
+    /// "two channels" rather than "red and green".
+    RG16 = 6,
+
+    /// Four channels, signed integer storage.
+    RGBAI32 = 7,
+    /// Four channels, byte storage.
+    RGBA8 = 8,
+}
+
+impl ImageFormat {
+    /// Returns the number of bytes per pixel for the given format.
+    pub fn bytes_per_pixel(self) -> i32 {
+        match self {
+            ImageFormat::R8 => 1,
+            ImageFormat::R16 => 2,
+            ImageFormat::BGRA8 => 4,
+            ImageFormat::RGBAF32 => 16,
+            ImageFormat::RG8 => 2,
+            ImageFormat::RG16 => 4,
+            ImageFormat::RGBAI32 => 16,
+            ImageFormat::RGBA8 => 4,
+        }
+    }
+}
+
+/// Specifies the color depth of an image. Currently only used for YUV images.
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum ColorDepth {
+    /// 8 bits image (most common)
+    Color8,
+    /// 10 bits image
+    Color10,
+    /// 12 bits image
+    Color12,
+    /// 16 bits image
+    Color16,
+}
+
+impl Default for ColorDepth {
+    fn default() -> Self {
+        ColorDepth::Color8
+    }
+}
+
+impl ColorDepth {
+    /// Return the numerical bit depth value for the type.
+    pub fn bit_depth(self) -> u32 {
+        match self {
+            ColorDepth::Color8 => 8,
+            ColorDepth::Color10 => 10,
+            ColorDepth::Color12 => 12,
+            ColorDepth::Color16 => 16,
+        }
+    }
+    /// 10 and 12 bits images are encoded using 16 bits integer, we need to
+    /// rescale the 10 or 12 bits value to extend to 16 bits.
+    pub fn rescaling_factor(self) -> f32 {
+        match self {
+            ColorDepth::Color8 => 1.0,
+            ColorDepth::Color10 => 64.0,
+            ColorDepth::Color12 => 16.0,
+            ColorDepth::Color16 => 1.0,
+        }
+    }
+}
+
+bitflags! {
+    /// Various flags that are part of an image descriptor.
+    #[derive(Deserialize, Serialize)]
+    pub struct ImageDescriptorFlags: u32 {
+        /// Whether this image is opaque, or has an alpha channel. Avoiding blending
+        /// for opaque surfaces is an important optimization.
+        const IS_OPAQUE = 1;
+        /// Whether to allow the driver to automatically generate mipmaps. If images
+        /// are already downscaled appropriately, mipmap generation can be wasted
+        /// work, and cause performance problems on some cards/drivers.
+        ///
+        /// See https://github.com/servo/webrender/pull/2555/
+        const ALLOW_MIPMAPS = 2;
+    }
+}
+
+/// Metadata (but not storage) describing an image In WebRender.
+#[derive(Copy, Clone, Debug, Deserialize, PartialEq, Serialize)]
+pub struct ImageDescriptor {
+    /// Format of the image data.
+    pub format: ImageFormat,
+    /// Width and length of the image data, in pixels.
+    pub size: DeviceIntSize,
+    /// The number of bytes from the start of one row to the next. If non-None,
+    /// `compute_stride` will return this value, otherwise it returns
+    /// `width * bpp`. Different source of images have different alignment
+    /// constraints for rows, so the stride isn't always equal to width * bpp.
+    pub stride: Option<i32>,
+    /// Offset in bytes of the first pixel of this image in its backing buffer.
+    /// This is used for tiling, wherein WebRender extracts chunks of input images
+    /// in order to cache, manipulate, and render them individually. This offset
+    /// tells the texture upload machinery where to find the bytes to upload for
+    /// this tile. Non-tiled images generally set this to zero.
+    pub offset: i32,
+    /// Various bool flags related to this descriptor.
+    pub flags: ImageDescriptorFlags,
+}
+
+impl ImageDescriptor {
+    /// Mints a new ImageDescriptor.
+    pub fn new(
+        width: i32,
+        height: i32,
+        format: ImageFormat,
+        flags: ImageDescriptorFlags,
+    ) -> Self {
+        ImageDescriptor {
+            size: size2(width, height),
+            format,
+            stride: None,
+            offset: 0,
+            flags,
+        }
+    }
+
+    /// Returns the stride, either via an explicit stride stashed on the object
+    /// or by the default computation.
+    pub fn compute_stride(&self) -> i32 {
+        self.stride.unwrap_or(self.size.width * self.format.bytes_per_pixel())
+    }
+
+    /// Computes the total size of the image, in bytes.
+    pub fn compute_total_size(&self) -> i32 {
+        self.compute_stride() * self.size.height
+    }
+
+    /// Computes the bounding rectangle for the image, rooted at (0, 0).
+    pub fn full_rect(&self) -> DeviceIntRect {
+        DeviceIntRect::new(
+            DeviceIntPoint::zero(),
+            self.size,
+        )
+    }
+
+    /// Returns true if this descriptor is opaque
+    pub fn is_opaque(&self) -> bool {
+        self.flags.contains(ImageDescriptorFlags::IS_OPAQUE)
+    }
+
+    /// Returns true if this descriptor allows mipmaps
+    pub fn allow_mipmaps(&self) -> bool {
+        self.flags.contains(ImageDescriptorFlags::ALLOW_MIPMAPS)
+    }
+}
+
+/// Represents the backing store of an arbitrary series of pixels for display by
+/// WebRender. This storage can take several forms.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub enum ImageData {
+    /// A simple series of bytes, provided by the embedding and owned by WebRender.
+    /// The format is stored out-of-band, currently in ImageDescriptor.
+    Raw(#[serde(with = "serde_image_data_raw")] Arc<Vec<u8>>),
+    /// An image owned by the embedding, and referenced by WebRender. This may
+    /// take the form of a texture or a heap-allocated buffer.
+    External(ExternalImageData),
+}
+
+mod serde_image_data_raw {
+    extern crate serde_bytes;
+
+    use std::sync::Arc;
+    use serde::{Deserializer, Serializer};
+
+    pub fn serialize<S: Serializer>(bytes: &Arc<Vec<u8>>, serializer: S) -> Result<S::Ok, S::Error> {
+        serde_bytes::serialize(bytes.as_slice(), serializer)
+    }
+
+    pub fn deserialize<'de, D: Deserializer<'de>>(deserializer: D) -> Result<Arc<Vec<u8>>, D::Error> {
+        serde_bytes::deserialize(deserializer).map(Arc::new)
+    }
+}
+
+impl ImageData {
+    /// Mints a new raw ImageData, taking ownership of the bytes.
+    pub fn new(bytes: Vec<u8>) -> Self {
+        ImageData::Raw(Arc::new(bytes))
+    }
+
+    /// Mints a new raw ImageData from Arc-ed bytes.
+    pub fn new_shared(bytes: Arc<Vec<u8>>) -> Self {
+        ImageData::Raw(bytes)
+    }
+}
+
+/// The resources exposed by the resource cache available for use by the blob rasterizer.
+pub trait BlobImageResources {
+    /// Returns the `FontTemplate` for the given key.
+    fn get_font_data(&self, key: FontKey) -> &FontTemplate;
+    /// Returns the `FontInstanceData` for the given key, if found.
+    fn get_font_instance_data(&self, key: FontInstanceKey) -> Option<FontInstanceData>;
+}
+
+/// A handler on the render backend that can create rasterizer objects which will
+/// be sent to the scene builder thread to execute the rasterization.
+///
+/// The handler is responsible for collecting resources, managing/updating blob commands
+/// and creating the rasterizer objects, but isn't expected to do any rasterization itself.
+pub trait BlobImageHandler: Send {
+    /// Creates a snapshot of the current state of blob images in the handler.
+    fn create_blob_rasterizer(&mut self) -> Box<dyn AsyncBlobImageRasterizer>;
+
+    /// Creates an empty blob handler of the same type.
+    ///
+    /// This is used to allow creating new API endpoints with blob handlers installed on them.
+    fn create_similar(&self) -> Box<dyn BlobImageHandler>;
+
+    /// A hook to let the blob image handler update any state related to resources that
+    /// are not bundled in the blob recording itself.
+    fn prepare_resources(
+        &mut self,
+        services: &dyn BlobImageResources,
+        requests: &[BlobImageParams],
+    );
+
+    /// Register a blob image.
+    fn add(&mut self, key: BlobImageKey, data: Arc<BlobImageData>, visible_rect: &DeviceIntRect,
+           tile_size: TileSize);
+
+    /// Update an already registered blob image.
+    fn update(&mut self, key: BlobImageKey, data: Arc<BlobImageData>, visible_rect: &DeviceIntRect,
+              dirty_rect: &BlobDirtyRect);
+
+    /// Delete an already registered blob image.
+    fn delete(&mut self, key: BlobImageKey);
+
+    /// A hook to let the handler clean up any state related to a font which the resource
+    /// cache is about to delete.
+    fn delete_font(&mut self, key: FontKey);
+
+    /// A hook to let the handler clean up any state related to a font instance which the
+    /// resource cache is about to delete.
+    fn delete_font_instance(&mut self, key: FontInstanceKey);
+
+    /// A hook to let the handler clean up any state related a given namespace before the
+    /// resource cache deletes them.
+    fn clear_namespace(&mut self, namespace: IdNamespace);
+
+    /// Whether to allow rendering blobs on multiple threads.
+    fn enable_multithreading(&mut self, enable: bool);
+}
+
+/// A group of rasterization requests to execute synchronously on the scene builder thread.
+pub trait AsyncBlobImageRasterizer : Send {
+    /// Rasterize the requests.
+    ///
+    /// Gecko uses te priority hint to schedule work in a way that minimizes the risk
+    /// of high priority work being blocked by (or enqued behind) low priority work.
+    fn rasterize(
+        &mut self,
+        requests: &[BlobImageParams],
+        low_priority: bool
+    ) -> Vec<(BlobImageRequest, BlobImageResult)>;
+}
+
+
+/// Input parameters for the BlobImageRasterizer.
+#[derive(Copy, Clone, Debug)]
+pub struct BlobImageParams {
+    /// A key that identifies the blob image rasterization request.
+    pub request: BlobImageRequest,
+    /// Description of the format of the blob's output image.
+    pub descriptor: BlobImageDescriptor,
+    /// An optional sub-rectangle of the image to avoid re-rasterizing
+    /// the entire image when only a portion is updated.
+    ///
+    /// If set to None the entire image is rasterized.
+    pub dirty_rect: BlobDirtyRect,
+}
+
+/// The possible states of a Dirty rect.
+///
+/// This exists because people kept getting confused with `Option<Rect>`.
+#[derive(Debug, Serialize, Deserialize)]
+pub enum DirtyRect<T: Copy, U> {
+    /// Everything is Dirty, equivalent to Partial(image_bounds)
+    All,
+    /// Some specific amount is dirty
+    Partial(Rect<T, U>)
+}
+
+impl<T, U> DirtyRect<T, U>
+where
+    T: Copy + Clone
+        + PartialOrd + PartialEq
+        + Add<T, Output = T>
+        + Sub<T, Output = T>
+        + Zero
+{
+    /// Creates an empty DirtyRect (indicating nothing is invalid)
+    pub fn empty() -> Self {
+        DirtyRect::Partial(Rect::zero())
+    }
+
+    /// Returns whether the dirty rect is empty
+    pub fn is_empty(&self) -> bool {
+        match self {
+            DirtyRect::All => false,
+            DirtyRect::Partial(rect) => rect.is_empty(),
+        }
+    }
+
+    /// Replaces self with the empty rect and returns the old value.
+    pub fn replace_with_empty(&mut self) -> Self {
+        ::std::mem::replace(self, DirtyRect::empty())
+    }
+
+    /// Maps over the contents of Partial.
+    pub fn map<F>(self, func: F) -> Self
+        where F: FnOnce(Rect<T, U>) -> Rect<T, U>,
+    {
+        use crate::DirtyRect::*;
+
+        match self {
+            All        => All,
+            Partial(rect) => Partial(func(rect)),
+        }
+    }
+
+    /// Unions the dirty rects.
+    pub fn union(&self, other: &Self) -> Self {
+        use crate::DirtyRect::*;
+
+        match (*self, *other) {
+            (All, _) | (_, All)        => All,
+            (Partial(rect1), Partial(rect2)) => Partial(rect1.union(&rect2)),
+        }
+    }
+
+    /// Intersects the dirty rects.
+    pub fn intersection(&self, other: &Self) -> Self {
+        use crate::DirtyRect::*;
+
+        match (*self, *other) {
+            (All, rect) | (rect, All)  => rect,
+            (Partial(rect1), Partial(rect2)) => {
+                Partial(rect1.intersection(&rect2).unwrap_or_else(Rect::zero))
+            }
+        }
+    }
+
+    /// Converts the dirty rect into a subrect of the given one via intersection.
+    pub fn to_subrect_of(&self, rect: &Rect<T, U>) -> Rect<T, U> {
+        use crate::DirtyRect::*;
+
+        match *self {
+            All => *rect,
+            Partial(dirty_rect) => {
+                dirty_rect.intersection(rect).unwrap_or_else(Rect::zero)
+            }
+        }
+    }
+}
+
+impl<T: Copy, U> Copy for DirtyRect<T, U> {}
+impl<T: Copy, U> Clone for DirtyRect<T, U> {
+    fn clone(&self) -> Self { *self }
+}
+
+impl<T: Copy, U> From<Rect<T, U>> for DirtyRect<T, U> {
+    fn from(rect: Rect<T, U>) -> Self {
+        DirtyRect::Partial(rect)
+    }
+}
+
+/// Backing store for blob image command streams.
+pub type BlobImageData = Vec<u8>;
+
+/// Result type for blob raserization.
+pub type BlobImageResult = Result<RasterizedBlobImage, BlobImageError>;
+
+/// Metadata (but not storage) for a blob image.
+#[repr(C)]
+#[derive(Copy, Clone, Debug)]
+pub struct BlobImageDescriptor {
+    /// Surface of the image or tile to render in the same coordinate space as
+    /// the drawing commands.
+    pub rect: LayoutIntRect,
+    /// Format for the data in the backing store.
+    pub format: ImageFormat,
+}
+
+/// Representation of a rasterized blob image. This is obtained by passing
+/// `BlobImageData` to the embedding via the rasterization callback.
+pub struct RasterizedBlobImage {
+    /// The rectangle that was rasterized in device pixels, relative to the
+    /// image or tile.
+    pub rasterized_rect: DeviceIntRect,
+    /// Backing store. The format is stored out of band in `BlobImageDescriptor`.
+    pub data: Arc<Vec<u8>>,
+}
+
+/// Error code for when blob rasterization failed.
+#[derive(Clone, Debug)]
+pub enum BlobImageError {
+    /// Out of memory.
+    Oom,
+    /// Other failure, embedding-specified.
+    Other(String),
+}
+
+
+
+/// A key identifying blob image rasterization work requested from the blob
+/// image rasterizer.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub struct BlobImageRequest {
+    /// Unique handle to the image.
+    pub key: BlobImageKey,
+    /// Tiling offset in number of tiles.
+    pub tile: TileOffset,
+}
diff --git a/gfx/wr/webrender_api/src/lib.rs b/gfx/wr/webrender_api/src/lib.rs
new file mode 100644
index 0000000000..72016421c8
--- /dev/null
+++ b/gfx/wr/webrender_api/src/lib.rs
@@ -0,0 +1,656 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! The `webrender_api` crate contains an assortment types and functions used
+//! by WebRender consumers as well as, in many cases, WebRender itself.
+//!
+//! This separation allows Servo to parallelize compilation across `webrender`
+//! and other crates that depend on `webrender_api`. So in practice, we put
+//! things in this crate when Servo needs to use them. Firefox depends on the
+//! `webrender` crate directly, and so this distinction is not really relevant
+//! there.
+
+#![cfg_attr(feature = "nightly", feature(nonzero))]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::float_cmp, clippy::too_many_arguments))]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::unreadable_literal, clippy::new_without_default))]
+
+pub extern crate crossbeam_channel;
+pub extern crate euclid;
+
+extern crate app_units;
+#[macro_use]
+extern crate bitflags;
+extern crate byteorder;
+#[cfg(feature = "nightly")]
+extern crate core;
+#[cfg(target_os = "macos")]
+extern crate core_foundation;
+#[cfg(target_os = "macos")]
+extern crate core_graphics;
+extern crate derive_more;
+#[macro_use]
+extern crate malloc_size_of_derive;
+extern crate serde;
+#[macro_use]
+extern crate serde_derive;
+extern crate time;
+
+extern crate malloc_size_of;
+extern crate peek_poke;
+
+pub mod channel;
+mod color;
+mod display_item;
+mod display_item_cache;
+mod display_list;
+mod font;
+mod gradient_builder;
+mod image;
+pub mod units;
+
+pub use crate::color::*;
+pub use crate::display_item::*;
+pub use crate::display_item_cache::DisplayItemCache;
+pub use crate::display_list::*;
+pub use crate::font::*;
+pub use crate::gradient_builder::*;
+pub use crate::image::*;
+
+use crate::units::*;
+use crate::channel::Receiver;
+use std::marker::PhantomData;
+use std::sync::Arc;
+use std::os::raw::c_void;
+use peek_poke::PeekPoke;
+
+/// Width and height in device pixels of image tiles.
+pub type TileSize = u16;
+
+/// Various settings that the caller can select based on desired tradeoffs
+/// between rendering quality and performance / power usage.
+#[derive(Copy, Clone, Deserialize, Serialize)]
+pub struct QualitySettings {
+    /// If true, disable creating separate picture cache slices when the
+    /// scroll root changes. This gives maximum opportunity to find an
+    /// opaque background, which enables subpixel AA. However, it is
+    /// usually significantly more expensive to render when scrolling.
+    pub force_subpixel_aa_where_possible: bool,
+}
+
+impl Default for QualitySettings {
+    fn default() -> Self {
+        QualitySettings {
+            // Prefer performance over maximum subpixel AA quality, since WR
+            // already enables subpixel AA in more situations than other browsers.
+            force_subpixel_aa_where_possible: false,
+        }
+    }
+}
+
+/// An epoch identifies the state of a pipeline in time.
+///
+/// This is mostly used as a synchronization mechanism to observe how/when particular pipeline
+/// updates propagate through WebRender and are applied at various stages.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize)]
+pub struct Epoch(pub u32);
+
+impl Epoch {
+    /// Magic invalid epoch value.
+    pub fn invalid() -> Epoch {
+        Epoch(u32::MAX)
+    }
+}
+
+/// ID namespaces uniquely identify different users of WebRender's API.
+///
+/// For example in Gecko each content process uses a separate id namespace.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Eq, MallocSizeOf, PartialEq, Hash, Ord, PartialOrd, PeekPoke)]
+#[derive(Deserialize, Serialize)]
+pub struct IdNamespace(pub u32);
+
+/// A key uniquely identifying a WebRender document.
+///
+/// Instances can manage one or several documents (using the same render backend thread).
+/// Each document will internally correspond to a single scene, and scenes are made of
+/// one or several pipelines.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct DocumentId {
+    ///
+    pub namespace_id: IdNamespace,
+    ///
+    pub id: u32,
+}
+
+impl DocumentId {
+    ///
+    pub fn new(namespace_id: IdNamespace, id: u32) -> Self {
+        DocumentId {
+            namespace_id,
+            id,
+        }
+    }
+
+    ///
+    pub const INVALID: DocumentId = DocumentId { namespace_id: IdNamespace(0), id: 0 };
+}
+
+/// This type carries no valuable semantics for WR. However, it reflects the fact that
+/// clients (Servo) may generate pipelines by different semi-independent sources.
+/// These pipelines still belong to the same `IdNamespace` and the same `DocumentId`.
+/// Having this extra Id field enables them to generate `PipelineId` without collision.
+pub type PipelineSourceId = u32;
+
+/// From the point of view of WR, `PipelineId` is completely opaque and generic as long as
+/// it's clonable, serializable, comparable, and hashable.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct PipelineId(pub PipelineSourceId, pub u32);
+
+impl Default for PipelineId {
+    fn default() -> Self {
+        PipelineId::dummy()
+    }
+}
+
+impl PipelineId {
+    ///
+    pub fn dummy() -> Self {
+        PipelineId(0, 0)
+    }
+}
+
+
+/// An opaque pointer-sized value.
+#[repr(C)]
+#[derive(Clone)]
+pub struct ExternalEvent {
+    raw: usize,
+}
+
+unsafe impl Send for ExternalEvent {}
+
+impl ExternalEvent {
+    /// Creates the event from an opaque pointer-sized value.
+    pub fn from_raw(raw: usize) -> Self {
+        ExternalEvent { raw }
+    }
+    /// Consumes self to make it obvious that the event should be forwarded only once.
+    pub fn unwrap(self) -> usize {
+        self.raw
+    }
+}
+
+/// Describe whether or not scrolling should be clamped by the content bounds.
+#[derive(Clone, Deserialize, Serialize)]
+pub enum ScrollClamping {
+    ///
+    ToContentBounds,
+    ///
+    NoClamping,
+}
+
+/// A handler to integrate WebRender with the thread that contains the `Renderer`.
+pub trait RenderNotifier: Send {
+    ///
+    fn clone(&self) -> Box<dyn RenderNotifier>;
+    /// Wake the thread containing the `Renderer` up (after updates have been put
+    /// in the renderer's queue).
+    fn wake_up(
+        &self,
+        composite_needed: bool,
+    );
+    /// Notify the thread containing the `Renderer` that a new frame is ready.
+    fn new_frame_ready(&self, _: DocumentId, scrolled: bool, composite_needed: bool, render_time_ns: Option<u64>);
+    /// A Gecko-specific notification mechanism to get some code executed on the
+    /// `Renderer`'s thread, mostly replaced by `NotificationHandler`. You should
+    /// probably use the latter instead.
+    fn external_event(&self, _evt: ExternalEvent) {
+        unimplemented!()
+    }
+    /// Notify the thread containing the `Renderer` that the render backend has been
+    /// shut down.
+    fn shut_down(&self) {}
+}
+
+/// A stage of the rendering pipeline.
+#[repr(u32)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Checkpoint {
+    ///
+    SceneBuilt,
+    ///
+    FrameBuilt,
+    ///
+    FrameTexturesUpdated,
+    ///
+    FrameRendered,
+    /// NotificationRequests get notified with this if they get dropped without having been
+    /// notified. This provides the guarantee that if a request is created it will get notified.
+    TransactionDropped,
+}
+
+/// A handler to notify when a transaction reaches certain stages of the rendering
+/// pipeline.
+pub trait NotificationHandler : Send + Sync {
+    /// Entry point of the handler to implement. Invoked by WebRender.
+    fn notify(&self, when: Checkpoint);
+}
+
+/// A request to notify a handler when the transaction reaches certain stages of the
+/// rendering pipeline.
+///
+/// The request is guaranteed to be notified once and only once, even if the transaction
+/// is dropped before the requested check-point.
+pub struct NotificationRequest {
+    handler: Option<Box<dyn NotificationHandler>>,
+    when: Checkpoint,
+}
+
+impl NotificationRequest {
+    /// Constructor.
+    pub fn new(when: Checkpoint, handler: Box<dyn NotificationHandler>) -> Self {
+        NotificationRequest {
+            handler: Some(handler),
+            when,
+        }
+    }
+
+    /// The specified stage at which point the handler should be notified.
+    pub fn when(&self) -> Checkpoint { self.when }
+
+    /// Called by WebRender at specified stages to notify the registered handler.
+    pub fn notify(mut self) {
+        if let Some(handler) = self.handler.take() {
+            handler.notify(self.when);
+        }
+    }
+}
+
+/// An object that can perform hit-testing without doing synchronous queries to
+/// the RenderBackendThread.
+pub trait ApiHitTester: Send + Sync {
+    /// Does a hit test on display items in the specified document, at the given
+    /// point. If a pipeline_id is specified, it is used to further restrict the
+    /// hit results so that only items inside that pipeline are matched. The vector
+    /// of hit results will contain all display items that match, ordered from
+    /// front to back.
+    fn hit_test(&self, pipeline_id: Option<PipelineId>, point: WorldPoint) -> HitTestResult;
+}
+
+/// A hit tester requested to the render backend thread but not necessarily ready yet.
+///
+/// The request should be resolved as late as possible to reduce the likelihood of blocking.
+pub struct HitTesterRequest {
+    #[doc(hidden)]
+    pub rx: Receiver<Arc<dyn ApiHitTester>>,
+}
+
+impl HitTesterRequest {
+    /// Block until the hit tester is available and return it, consuming teh request.
+    pub fn resolve(self) -> Arc<dyn ApiHitTester> {
+        self.rx.recv().unwrap()
+    }
+}
+
+/// Describe an item that matched a hit-test query.
+#[derive(Clone, Debug, Deserialize, PartialEq, Serialize)]
+pub struct HitTestItem {
+    /// The pipeline that the display item that was hit belongs to.
+    pub pipeline: PipelineId,
+
+    /// The tag of the hit display item.
+    pub tag: ItemTag,
+
+    /// The hit point in the coordinate space of the "viewport" of the display item. The
+    /// viewport is the scroll node formed by the root reference frame of the display item's
+    /// pipeline.
+    pub point_in_viewport: LayoutPoint,
+
+    /// The coordinates of the original hit test point relative to the origin of this item.
+    /// This is useful for calculating things like text offsets in the client.
+    pub point_relative_to_item: LayoutPoint,
+}
+
+/// Returned by `RenderApi::hit_test`.
+#[derive(Clone, Debug, Default, Deserialize, Serialize)]
+pub struct HitTestResult {
+    /// List of items that are match the hit-test query.
+    pub items: Vec<HitTestItem>,
+}
+
+impl Drop for NotificationRequest {
+    fn drop(&mut self) {
+        if let Some(ref mut handler) = self.handler {
+            handler.notify(Checkpoint::TransactionDropped);
+        }
+    }
+}
+
+// This Clone impl yields an "empty" request because we don't want the requests
+// to be notified twice so the request is owned by only one of the API messages
+// (the original one) after the clone.
+// This works in practice because the notifications requests are used for
+// synchronization so we don't need to include them in the recording mechanism
+// in wrench that clones the messages.
+impl Clone for NotificationRequest {
+    fn clone(&self) -> Self {
+        NotificationRequest {
+            when: self.when,
+            handler: None,
+        }
+    }
+}
+
+
+/// A key to identify an animated property binding.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, MallocSizeOf, PartialEq, Serialize, Eq, Hash, PeekPoke)]
+pub struct PropertyBindingId {
+    pub namespace: IdNamespace,
+    pub uid: u32,
+}
+
+impl PropertyBindingId {
+    /// Constructor.
+    pub fn new(value: u64) -> Self {
+        PropertyBindingId {
+            namespace: IdNamespace((value >> 32) as u32),
+            uid: value as u32,
+        }
+    }
+}
+
+/// A unique key that is used for connecting animated property
+/// values to bindings in the display list.
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub struct PropertyBindingKey<T> {
+    ///
+    pub id: PropertyBindingId,
+    #[doc(hidden)]
+    pub _phantom: PhantomData<T>,
+}
+
+/// Construct a property value from a given key and value.
+impl<T: Copy> PropertyBindingKey<T> {
+    ///
+    pub fn with(self, value: T) -> PropertyValue<T> {
+        PropertyValue { key: self, value }
+    }
+}
+
+impl<T> PropertyBindingKey<T> {
+    /// Constructor.
+    pub fn new(value: u64) -> Self {
+        PropertyBindingKey {
+            id: PropertyBindingId::new(value),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+/// A binding property can either be a specific value
+/// (the normal, non-animated case) or point to a binding location
+/// to fetch the current value from.
+/// Note that Binding has also a non-animated value, the value is
+/// used for the case where the animation is still in-delay phase
+/// (i.e. the animation doesn't produce any animation values).
+#[repr(C)]
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize, PeekPoke)]
+pub enum PropertyBinding<T> {
+    /// Non-animated value.
+    Value(T),
+    /// Animated binding.
+    Binding(PropertyBindingKey<T>, T),
+}
+
+impl<T: Default> Default for PropertyBinding<T> {
+    fn default() -> Self {
+        PropertyBinding::Value(Default::default())
+    }
+}
+
+impl<T> From<T> for PropertyBinding<T> {
+    fn from(value: T) -> PropertyBinding<T> {
+        PropertyBinding::Value(value)
+    }
+}
+
+impl From<PropertyBindingKey<ColorF>> for PropertyBindingKey<ColorU> {
+    fn from(key: PropertyBindingKey<ColorF>) -> PropertyBindingKey<ColorU> {
+        PropertyBindingKey {
+            id: key.id.clone(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl From<PropertyBindingKey<ColorU>> for PropertyBindingKey<ColorF> {
+    fn from(key: PropertyBindingKey<ColorU>) -> PropertyBindingKey<ColorF> {
+        PropertyBindingKey {
+            id: key.id.clone(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl From<PropertyBinding<ColorF>> for PropertyBinding<ColorU> {
+    fn from(value: PropertyBinding<ColorF>) -> PropertyBinding<ColorU> {
+        match value {
+            PropertyBinding::Value(value) => PropertyBinding::Value(value.into()),
+            PropertyBinding::Binding(k, v) => {
+                PropertyBinding::Binding(k.into(), v.into())
+            }
+        }
+    }
+}
+
+impl From<PropertyBinding<ColorU>> for PropertyBinding<ColorF> {
+    fn from(value: PropertyBinding<ColorU>) -> PropertyBinding<ColorF> {
+        match value {
+            PropertyBinding::Value(value) => PropertyBinding::Value(value.into()),
+            PropertyBinding::Binding(k, v) => {
+                PropertyBinding::Binding(k.into(), v.into())
+            }
+        }
+    }
+}
+
+/// The current value of an animated property. This is
+/// supplied by the calling code.
+#[derive(Clone, Copy, Debug, Deserialize, Serialize, PartialEq)]
+pub struct PropertyValue<T> {
+    ///
+    pub key: PropertyBindingKey<T>,
+    ///
+    pub value: T,
+}
+
+/// When using `generate_frame()`, a list of `PropertyValue` structures
+/// can optionally be supplied to provide the current value of any
+/// animated properties.
+#[derive(Clone, Deserialize, Serialize, Debug, PartialEq, Default)]
+pub struct DynamicProperties {
+    ///
+    pub transforms: Vec<PropertyValue<LayoutTransform>>,
+    /// opacity
+    pub floats: Vec<PropertyValue<f32>>,
+    /// background color
+    pub colors: Vec<PropertyValue<ColorF>>,
+}
+
+/// A C function that takes a pointer to a heap allocation and returns its size.
+///
+/// This is borrowed from the malloc_size_of crate, upon which we want to avoid
+/// a dependency from WebRender.
+pub type VoidPtrToSizeFn = unsafe extern "C" fn(ptr: *const c_void) -> usize;
+
+bitflags! {
+    /// Flags to enable/disable various builtin debugging tools.
+    #[repr(C)]
+    #[derive(Default, Deserialize, MallocSizeOf, Serialize)]
+    pub struct DebugFlags: u32 {
+        /// Display the frame profiler on screen.
+        const PROFILER_DBG          = 1 << 0;
+        /// Display intermediate render targets on screen.
+        const RENDER_TARGET_DBG     = 1 << 1;
+        /// Display all texture cache pages on screen.
+        const TEXTURE_CACHE_DBG     = 1 << 2;
+        /// Display GPU timing results.
+        const GPU_TIME_QUERIES      = 1 << 3;
+        /// Query the number of pixels that pass the depth test divided and show it
+        /// in the profiler as a percentage of the number of pixels in the screen
+        /// (window width times height).
+        const GPU_SAMPLE_QUERIES    = 1 << 4;
+        /// Render each quad with their own draw call.
+        ///
+        /// Terrible for performance but can help with understanding the drawing
+        /// order when inspecting renderdoc or apitrace recordings.
+        const DISABLE_BATCHING      = 1 << 5;
+        /// Display the pipeline epochs.
+        const EPOCHS                = 1 << 6;
+        /// Print driver messages to stdout.
+        const ECHO_DRIVER_MESSAGES  = 1 << 7;
+        /// Show an overlay displaying overdraw amount.
+        const SHOW_OVERDRAW         = 1 << 8;
+        /// Display the contents of GPU cache.
+        const GPU_CACHE_DBG         = 1 << 9;
+        /// Clear evicted parts of the texture cache for debugging purposes.
+        const TEXTURE_CACHE_DBG_CLEAR_EVICTED = 1 << 10;
+        /// Show picture caching debug overlay
+        const PICTURE_CACHING_DBG   = 1 << 11;
+        /// Highlight all primitives with colors based on kind.
+        const PRIMITIVE_DBG = 1 << 12;
+        /// Draw a zoom widget showing part of the framebuffer zoomed in.
+        const ZOOM_DBG = 1 << 13;
+        /// Scale the debug renderer down for a smaller screen. This will disrupt
+        /// any mapping between debug display items and page content, so shouldn't
+        /// be used with overlays like the picture caching or primitive display.
+        const SMALL_SCREEN = 1 << 14;
+        /// Disable various bits of the WebRender pipeline, to help narrow
+        /// down where slowness might be coming from.
+        const DISABLE_OPAQUE_PASS = 1 << 15;
+        ///
+        const DISABLE_ALPHA_PASS = 1 << 16;
+        ///
+        const DISABLE_CLIP_MASKS = 1 << 17;
+        ///
+        const DISABLE_TEXT_PRIMS = 1 << 18;
+        ///
+        const DISABLE_GRADIENT_PRIMS = 1 << 19;
+        ///
+        const OBSCURE_IMAGES = 1 << 20;
+        /// Taint the transparent area of the glyphs with a random opacity to easily
+        /// see when glyphs are re-rasterized.
+        const GLYPH_FLASHING = 1 << 21;
+        /// The profiler only displays information that is out of the ordinary.
+        const SMART_PROFILER        = 1 << 22;
+        /// If set, dump picture cache invalidation debug to console.
+        const INVALIDATION_DBG = 1 << 23;
+        /// Log tile cache to memory for later saving as part of wr-capture
+        const TILE_CACHE_LOGGING_DBG   = 1 << 24;
+        /// Collect and dump profiler statistics to captures.
+        const PROFILER_CAPTURE = (1 as u32) << 25; // need "as u32" until we have cbindgen#556
+        /// Invalidate picture tiles every frames (useful when inspecting GPU work in external tools).
+        const FORCE_PICTURE_INVALIDATION = (1 as u32) << 26;
+    }
+}
+
+/// Information specific to a primitive type that
+/// uniquely identifies a primitive template by key.
+#[derive(Debug, Clone, Eq, MallocSizeOf, PartialEq, Hash, Serialize, Deserialize)]
+pub enum PrimitiveKeyKind {
+    /// Clear an existing rect, used for special effects on some platforms.
+    Clear,
+    ///
+    Rectangle {
+        ///
+        color: PropertyBinding<ColorU>,
+    },
+}
+
+///
+#[derive(Clone)]
+pub struct ScrollNodeState {
+    ///
+    pub id: ExternalScrollId,
+    ///
+    pub scroll_offset: LayoutVector2D,
+}
+
+///
+#[derive(Clone, Copy, Debug)]
+pub enum ScrollLocation {
+    /// Scroll by a certain amount.
+    Delta(LayoutVector2D),
+    /// Scroll to very top of element.
+    Start,
+    /// Scroll to very bottom of element.
+    End,
+}
+
+/// Represents a zoom factor.
+#[derive(Clone, Copy, Debug)]
+pub struct ZoomFactor(f32);
+
+impl ZoomFactor {
+    /// Construct a new zoom factor.
+    pub fn new(scale: f32) -> Self {
+        ZoomFactor(scale)
+    }
+
+    /// Get the zoom factor as an untyped float.
+    pub fn get(self) -> f32 {
+        self.0
+    }
+}
+
+/// Crash annotations included in crash reports.
+#[repr(C)]
+#[derive(Clone, Copy)]
+pub enum CrashAnnotation {
+    CompileShader = 0,
+}
+
+/// Handler to expose support for annotating crash reports.
+pub trait CrashAnnotator : Send {
+    fn set(&self, annotation: CrashAnnotation, value: &str);
+    fn clear(&self, annotation: CrashAnnotation);
+    fn box_clone(&self) -> Box<dyn CrashAnnotator>;
+}
+
+impl Clone for Box<dyn CrashAnnotator> {
+    fn clone(&self) -> Box<dyn CrashAnnotator> {
+        self.box_clone()
+    }
+}
+
+/// Guard to add a crash annotation at creation, and clear it at destruction.
+pub struct CrashAnnotatorGuard<'a> {
+    annotator: &'a Option<Box<dyn CrashAnnotator>>,
+    annotation: CrashAnnotation,
+}
+
+impl<'a> CrashAnnotatorGuard<'a> {
+    pub fn new(annotator: &'a Option<Box<dyn CrashAnnotator>>, annotation: CrashAnnotation, value: &str) -> Self {
+        if let Some(ref annotator) = annotator {
+            annotator.set(annotation, value);
+        }
+        Self {
+            annotator,
+            annotation,
+        }
+    }
+}
+
+impl<'a> Drop for CrashAnnotatorGuard<'a> {
+    fn drop(&mut self) {
+        if let Some(ref annotator) = self.annotator {
+            annotator.clear(self.annotation);
+        }
+    }
+}
diff --git a/gfx/wr/webrender_api/src/units.rs b/gfx/wr/webrender_api/src/units.rs
new file mode 100644
index 0000000000..9913e4e664
--- /dev/null
+++ b/gfx/wr/webrender_api/src/units.rs
@@ -0,0 +1,324 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! A collection of coordinate spaces and their corresponding Point, Size and Rect types.
+//!
+//! Physical pixels take into account the device pixel ratio and their dimensions tend
+//! to correspond to the allocated size of resources in memory, while logical pixels
+//! don't have the device pixel ratio applied which means they are agnostic to the usage
+//! of hidpi screens and the like.
+//!
+//! The terms "layer" and "stacking context" can be used interchangeably
+//! in the context of coordinate systems.
+
+pub use app_units::Au;
+use euclid::{Length, Rect, Scale, Size2D, Transform3D, Translation2D};
+use euclid::{Point2D, Point3D, Vector2D, Vector3D, SideOffsets2D, Box2D};
+use euclid::HomogeneousVector;
+use peek_poke::PeekPoke;
+// local imports
+use crate::image::DirtyRect;
+
+/// Geometry in the coordinate system of the render target (screen or intermediate
+/// surface) in physical pixels.
+#[derive(Hash, Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, Serialize, Deserialize)]
+pub struct DevicePixel;
+
+pub type DeviceIntRect = Rect<i32, DevicePixel>;
+pub type DeviceIntPoint = Point2D<i32, DevicePixel>;
+pub type DeviceIntSize = Size2D<i32, DevicePixel>;
+pub type DeviceIntLength = Length<i32, DevicePixel>;
+pub type DeviceIntSideOffsets = SideOffsets2D<i32, DevicePixel>;
+
+pub type DeviceRect = Rect<f32, DevicePixel>;
+pub type DevicePoint = Point2D<f32, DevicePixel>;
+pub type DeviceVector2D = Vector2D<f32, DevicePixel>;
+pub type DeviceSize = Size2D<f32, DevicePixel>;
+pub type DeviceHomogeneousVector = HomogeneousVector<f32, DevicePixel>;
+
+/// Geometry in the coordinate system of the framebuffer in physical pixels.
+/// It's Y-flipped comparing to DevicePixel.
+#[derive(Hash, Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, Serialize, Deserialize)]
+pub struct FramebufferPixel;
+
+pub type FramebufferIntPoint = Point2D<i32, FramebufferPixel>;
+pub type FramebufferIntSize = Size2D<i32, FramebufferPixel>;
+pub type FramebufferIntRect = Rect<i32, FramebufferPixel>;
+
+/// Geometry in the coordinate system of a Picture (intermediate
+/// surface) in physical pixels.
+#[derive(Hash, Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd)]
+pub struct PicturePixel;
+
+pub type PictureIntRect = Rect<i32, PicturePixel>;
+pub type PictureIntPoint = Point2D<i32, PicturePixel>;
+pub type PictureIntSize = Size2D<i32, PicturePixel>;
+pub type PictureRect = Rect<f32, PicturePixel>;
+pub type PicturePoint = Point2D<f32, PicturePixel>;
+pub type PictureSize = Size2D<f32, PicturePixel>;
+pub type PicturePoint3D = Point3D<f32, PicturePixel>;
+pub type PictureVector2D = Vector2D<f32, PicturePixel>;
+pub type PictureVector3D = Vector3D<f32, PicturePixel>;
+pub type PictureBox2D = Box2D<f32, PicturePixel>;
+
+/// Geometry gets rasterized in a given root coordinate space. This
+/// is often the root spatial node (world space), but may be a local
+/// space for a variety of reasons (e.g. perspective).
+#[derive(Hash, Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd)]
+pub struct RasterPixel;
+
+pub type RasterIntRect = Rect<i32, RasterPixel>;
+pub type RasterIntPoint = Point2D<i32, RasterPixel>;
+pub type RasterIntSize = Size2D<i32, RasterPixel>;
+pub type RasterRect = Rect<f32, RasterPixel>;
+pub type RasterPoint = Point2D<f32, RasterPixel>;
+pub type RasterSize = Size2D<f32, RasterPixel>;
+pub type RasterPoint3D = Point3D<f32, RasterPixel>;
+pub type RasterVector2D = Vector2D<f32, RasterPixel>;
+pub type RasterVector3D = Vector3D<f32, RasterPixel>;
+
+/// Geometry in a stacking context's local coordinate space (logical pixels).
+#[derive(Hash, Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, Ord, PartialOrd, Deserialize, Serialize, PeekPoke)]
+pub struct LayoutPixel;
+
+pub type LayoutRect = Rect<f32, LayoutPixel>;
+pub type LayoutPoint = Point2D<f32, LayoutPixel>;
+pub type LayoutPoint3D = Point3D<f32, LayoutPixel>;
+pub type LayoutVector2D = Vector2D<f32, LayoutPixel>;
+pub type LayoutVector3D = Vector3D<f32, LayoutPixel>;
+pub type LayoutSize = Size2D<f32, LayoutPixel>;
+pub type LayoutSideOffsets = SideOffsets2D<f32, LayoutPixel>;
+
+pub type LayoutIntRect = Rect<i32, LayoutPixel>;
+pub type LayoutIntPoint = Point2D<i32, LayoutPixel>;
+pub type LayoutIntSize = Size2D<i32, LayoutPixel>;
+
+/// Geometry in the document's coordinate space (logical pixels).
+#[derive(Hash, Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, Ord, PartialOrd)]
+pub struct WorldPixel;
+
+pub type WorldRect = Rect<f32, WorldPixel>;
+pub type WorldPoint = Point2D<f32, WorldPixel>;
+pub type WorldSize = Size2D<f32, WorldPixel>;
+pub type WorldPoint3D = Point3D<f32, WorldPixel>;
+pub type WorldVector2D = Vector2D<f32, WorldPixel>;
+pub type WorldVector3D = Vector3D<f32, WorldPixel>;
+
+/// Offset in number of tiles.
+#[derive(Hash, Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd)]
+pub struct Tiles;
+pub type TileOffset = Point2D<i32, Tiles>;
+pub type TileRange = Rect<i32, Tiles>;
+
+/// Scaling ratio from world pixels to device pixels.
+pub type DevicePixelScale = Scale<f32, WorldPixel, DevicePixel>;
+/// Scaling ratio from layout to world. Used for cases where we know the layout
+/// is in world space, or specifically want to treat it this way.
+pub type LayoutToWorldScale = Scale<f32, LayoutPixel, WorldPixel>;
+/// A complete scaling ratio from layout space to device pixel space.
+pub type LayoutToDeviceScale = Scale<f32, LayoutPixel, DevicePixel>;
+
+pub type LayoutTransform = Transform3D<f32, LayoutPixel, LayoutPixel>;
+pub type LayoutToWorldTransform = Transform3D<f32, LayoutPixel, WorldPixel>;
+pub type WorldToLayoutTransform = Transform3D<f32, WorldPixel, LayoutPixel>;
+
+pub type LayoutToPictureTransform = Transform3D<f32, LayoutPixel, PicturePixel>;
+pub type PictureToLayoutTransform = Transform3D<f32, PicturePixel, LayoutPixel>;
+
+pub type LayoutToRasterTransform = Transform3D<f32, LayoutPixel, RasterPixel>;
+pub type RasterToLayoutTransform = Transform3D<f32, RasterPixel, LayoutPixel>;
+
+pub type PictureToRasterTransform = Transform3D<f32, PicturePixel, RasterPixel>;
+pub type RasterToPictureTransform = Transform3D<f32, RasterPixel, PicturePixel>;
+
+// Fixed position coordinates, to avoid float precision errors.
+pub type LayoutPointAu = Point2D<Au, LayoutPixel>;
+pub type LayoutRectAu = Rect<Au, LayoutPixel>;
+pub type LayoutSizeAu = Size2D<Au, LayoutPixel>;
+pub type LayoutVector2DAu = Vector2D<Au, LayoutPixel>;
+pub type LayoutSideOffsetsAu = SideOffsets2D<Au, LayoutPixel>;
+
+pub type ImageDirtyRect = DirtyRect<i32, DevicePixel>;
+pub type BlobDirtyRect = DirtyRect<i32, LayoutPixel>;
+
+pub type BlobToDeviceTranslation = Translation2D<i32, LayoutPixel, DevicePixel>;
+
+/// Stores two coordinates in texel space. The coordinates
+/// are stored in texel coordinates because the texture atlas
+/// may grow. Storing them as texel coords and normalizing
+/// the UVs in the vertex shader means nothing needs to be
+/// updated on the CPU when the texture size changes.
+#[derive(Copy, Clone, Debug, Serialize, Deserialize)]
+pub struct TexelRect {
+    pub uv0: DevicePoint,
+    pub uv1: DevicePoint,
+}
+
+impl TexelRect {
+    pub fn new(u0: f32, v0: f32, u1: f32, v1: f32) -> Self {
+        TexelRect {
+            uv0: DevicePoint::new(u0, v0),
+            uv1: DevicePoint::new(u1, v1),
+        }
+    }
+
+    pub fn invalid() -> Self {
+        TexelRect {
+            uv0: DevicePoint::new(-1.0, -1.0),
+            uv1: DevicePoint::new(-1.0, -1.0),
+        }
+    }
+}
+
+impl Into<TexelRect> for DeviceIntRect {
+    fn into(self) -> TexelRect {
+        TexelRect {
+            uv0: self.min().to_f32(),
+            uv1: self.max().to_f32(),
+        }
+    }
+}
+
+const MAX_AU_FLOAT: f32 = 1.0e6;
+
+pub trait AuHelpers<T> {
+    fn from_au(data: T) -> Self;
+    fn to_au(&self) -> T;
+}
+
+impl AuHelpers<LayoutSizeAu> for LayoutSize {
+    fn from_au(size: LayoutSizeAu) -> Self {
+        LayoutSize::new(
+            size.width.to_f32_px(),
+            size.height.to_f32_px(),
+        )
+    }
+
+    fn to_au(&self) -> LayoutSizeAu {
+        let width = self.width.min(2.0 * MAX_AU_FLOAT);
+        let height = self.height.min(2.0 * MAX_AU_FLOAT);
+
+        LayoutSizeAu::new(
+            Au::from_f32_px(width),
+            Au::from_f32_px(height),
+        )
+    }
+}
+
+impl AuHelpers<LayoutVector2DAu> for LayoutVector2D {
+    fn from_au(size: LayoutVector2DAu) -> Self {
+        LayoutVector2D::new(
+            size.x.to_f32_px(),
+            size.y.to_f32_px(),
+        )
+    }
+
+    fn to_au(&self) -> LayoutVector2DAu {
+        LayoutVector2DAu::new(
+            Au::from_f32_px(self.x),
+            Au::from_f32_px(self.y),
+        )
+    }
+}
+
+impl AuHelpers<LayoutPointAu> for LayoutPoint {
+    fn from_au(point: LayoutPointAu) -> Self {
+        LayoutPoint::new(
+            point.x.to_f32_px(),
+            point.y.to_f32_px(),
+        )
+    }
+
+    fn to_au(&self) -> LayoutPointAu {
+        let x = self.x.min(MAX_AU_FLOAT).max(-MAX_AU_FLOAT);
+        let y = self.y.min(MAX_AU_FLOAT).max(-MAX_AU_FLOAT);
+
+        LayoutPointAu::new(
+            Au::from_f32_px(x),
+            Au::from_f32_px(y),
+        )
+    }
+}
+
+impl AuHelpers<LayoutRectAu> for LayoutRect {
+    fn from_au(rect: LayoutRectAu) -> Self {
+        LayoutRect::new(
+            LayoutPoint::from_au(rect.origin),
+            LayoutSize::from_au(rect.size),
+        )
+    }
+
+    fn to_au(&self) -> LayoutRectAu {
+        LayoutRectAu::new(
+            self.origin.to_au(),
+            self.size.to_au(),
+        )
+    }
+}
+
+impl AuHelpers<LayoutSideOffsetsAu> for LayoutSideOffsets {
+    fn from_au(offsets: LayoutSideOffsetsAu) -> Self {
+        LayoutSideOffsets::new(
+            offsets.top.to_f32_px(),
+            offsets.right.to_f32_px(),
+            offsets.bottom.to_f32_px(),
+            offsets.left.to_f32_px(),
+        )
+    }
+
+    fn to_au(&self) -> LayoutSideOffsetsAu {
+        LayoutSideOffsetsAu::new(
+            Au::from_f32_px(self.top),
+            Au::from_f32_px(self.right),
+            Au::from_f32_px(self.bottom),
+            Au::from_f32_px(self.left),
+        )
+    }
+}
+
+pub trait RectExt {
+    type Point;
+    fn top_left(&self) -> Self::Point;
+    fn top_right(&self) -> Self::Point;
+    fn bottom_left(&self) -> Self::Point;
+    fn bottom_right(&self) -> Self::Point;
+}
+
+impl<U> RectExt for Rect<f32, U> {
+    type Point = Point2D<f32, U>;
+    fn top_left(&self) -> Self::Point {
+        self.min()
+    }
+    fn top_right(&self) -> Self::Point {
+        Point2D::new(self.max_x(), self.min_y())
+    }
+    fn bottom_left(&self) -> Self::Point {
+        Point2D::new(self.min_x(), self.max_y())
+    }
+    fn bottom_right(&self) -> Self::Point {
+        self.max()
+    }
+}
+
+// A few helpers to convert to cast between coordinate spaces that are often equivalent.
+
+#[inline]
+pub fn layout_rect_as_picture_rect(layout_rect: &LayoutRect) -> PictureRect {
+    layout_rect.cast_unit()
+}
+
+#[inline]
+pub fn layout_vector_as_picture_vector(layout_vector: LayoutVector2D) -> PictureVector2D {
+    layout_vector.cast_unit()
+}
+
+#[inline]
+pub fn device_size_as_framebuffer_size(framebuffer_size: DeviceIntSize) -> FramebufferIntSize {
+    framebuffer_size.cast_unit()
+}
+
+#[inline]
+pub fn device_rect_as_framebuffer_rect(framebuffer_rect: &DeviceIntRect) -> FramebufferIntRect {
+    framebuffer_rect.cast_unit()
+}