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diff --git a/gfx/wr/example-compositor/compositor/src/main.rs b/gfx/wr/example-compositor/compositor/src/main.rs
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+/* 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/. */
+
+/*
+
+   An example of how to implement the Compositor trait that
+   allows picture caching surfaces to be composited by the operating
+   system.
+
+   The current example supports DirectComposite on Windows only.
+
+*/
+
+use euclid::Angle;
+use gleam::gl;
+use std::ffi::CString;
+use std::sync::mpsc;
+use webrender::{CompositorSurfaceTransform, Transaction, api::*};
+use webrender::api::units::*;
+use webrender::Device;
+#[cfg(target_os = "windows")]
+use compositor_windows as compositor;
+#[cfg(target_os = "linux")]
+use compositor_wayland as compositor;
+use std::{env, f32, process};
+
+// A very hacky integration with DirectComposite. It proxies calls from the compositor
+// interface to a simple C99 library which does the DirectComposition / D3D11 / ANGLE
+// interfacing. This is a very unsafe impl due to the way the window pointer is passed
+// around!
+struct DirectCompositeInterface {
+    window: *mut compositor::Window,
+}
+
+impl DirectCompositeInterface {
+    fn new(window: *mut compositor::Window) -> Self {
+        DirectCompositeInterface { window }
+    }
+}
+
+impl webrender::Compositor for DirectCompositeInterface {
+    fn create_surface(
+        &mut self,
+        _device: &mut Device,
+        id: webrender::NativeSurfaceId,
+        _virtual_offset: DeviceIntPoint,
+        tile_size: DeviceIntSize,
+        is_opaque: bool,
+    ) {
+        compositor::create_surface(
+            self.window,
+            id.0,
+            tile_size.width,
+            tile_size.height,
+            is_opaque,
+        );
+    }
+
+    fn destroy_surface(&mut self, _device: &mut Device, id: webrender::NativeSurfaceId) {
+        compositor::destroy_surface(self.window, id.0);
+    }
+
+    fn create_tile(&mut self, _device: &mut Device, id: webrender::NativeTileId) {
+        compositor::create_tile(self.window, id.surface_id.0, id.x, id.y);
+    }
+
+    fn destroy_tile(&mut self, _device: &mut Device, id: webrender::NativeTileId) {
+        compositor::destroy_tile(self.window, id.surface_id.0, id.x, id.y);
+    }
+
+    fn bind(
+        &mut self,
+        _device: &mut Device,
+        id: webrender::NativeTileId,
+        dirty_rect: DeviceIntRect,
+        _valid_rect: DeviceIntRect,
+    ) -> webrender::NativeSurfaceInfo {
+        let (fbo_id, x, y) = compositor::bind_surface(
+            self.window,
+            id.surface_id.0,
+            id.x,
+            id.y,
+            dirty_rect.min.x,
+            dirty_rect.min.y,
+            dirty_rect.width(),
+            dirty_rect.height(),
+        );
+
+        webrender::NativeSurfaceInfo {
+            origin: DeviceIntPoint::new(x, y),
+            fbo_id,
+        }
+    }
+
+    fn unbind(&mut self, _device: &mut Device) {
+        compositor::unbind_surface(self.window);
+    }
+
+    fn begin_frame(&mut self, _device: &mut Device) {
+        compositor::begin_transaction(self.window);
+    }
+
+    fn add_surface(
+        &mut self,
+        _device: &mut Device,
+        id: webrender::NativeSurfaceId,
+        transform: CompositorSurfaceTransform,
+        clip_rect: DeviceIntRect,
+        _image_rendering: ImageRendering,
+    ) {
+        compositor::add_surface(
+            self.window,
+            id.0,
+            transform.offset.x as i32,
+            transform.offset.y as i32,
+            clip_rect.min.x,
+            clip_rect.min.y,
+            clip_rect.width(),
+            clip_rect.height(),
+        );
+    }
+
+    fn end_frame(&mut self, _device: &mut Device) {
+        compositor::end_transaction(self.window);
+    }
+    fn create_external_surface(
+        &mut self,
+        _device: &mut Device,
+        _id: webrender::NativeSurfaceId,
+        _: bool,
+    ) {
+        todo!()
+    }
+
+    fn attach_external_image(
+        &mut self,
+        _device: &mut Device,
+        _id: webrender::NativeSurfaceId,
+        _external_image: ExternalImageId,
+    ) {
+        todo!()
+    }
+
+    fn enable_native_compositor(&mut self, _device: &mut Device, _enable: bool) {
+        todo!()
+    }
+
+    fn deinit(&mut self, _device: &mut Device) {
+        compositor::deinit(self.window);
+    }
+
+    fn get_capabilities(&self, _device: &mut Device) -> webrender::CompositorCapabilities {
+        webrender::CompositorCapabilities {
+            virtual_surface_size: 1024 * 1024,
+            ..Default::default()
+        }
+    }
+
+    fn invalidate_tile(
+        &mut self,
+        _device: &mut Device,
+        _id: webrender::NativeTileId,
+        _valid_rect: DeviceIntRect,
+    ) {
+    }
+
+    fn start_compositing(
+        &mut self,
+        _device: &mut Device,
+        _color: webrender::webrender_api::ColorF,
+        _dirty_rects: &[DeviceIntRect],
+        _opaque_rects: &[DeviceIntRect],
+    ) {
+    }
+
+    fn create_backdrop_surface(
+        &mut self,
+        _device: &mut Device,
+        _id: webrender::NativeSurfaceId,
+        _color: webrender::webrender_api::ColorF,
+    ) {
+        todo!()
+    }
+
+    fn get_window_visibility(&self, _device: &mut Device) -> webrender::WindowVisibility {
+        todo!()
+    }
+}
+
+// Simplisitic implementation of the WR notifier interface to know when a frame
+// has been prepared and can be rendered.
+struct Notifier {
+    tx: mpsc::Sender<()>,
+}
+
+impl Notifier {
+    fn new(tx: mpsc::Sender<()>) -> Self {
+        Notifier { tx }
+    }
+}
+
+impl RenderNotifier for Notifier {
+    fn clone(&self) -> Box<dyn RenderNotifier> {
+        Box::new(Notifier {
+            tx: self.tx.clone(),
+        })
+    }
+
+    fn wake_up(&self, _composite_needed: bool) {}
+
+    fn new_frame_ready(&self, _: DocumentId, _scrolled: bool, _composite_needed: bool, _: FramePublishId) {
+        self.tx.send(()).ok();
+    }
+}
+
+fn push_rotated_rect(
+    builder: &mut DisplayListBuilder,
+    rect: LayoutRect,
+    color: ColorF,
+    spatial_id: SpatialId,
+    _root_pipeline_id: PipelineId,
+    angle: f32,
+    time: f32,
+    item_key: SpatialTreeItemKey,
+) {
+    let color = color.scale_rgb(time);
+    let rotation = LayoutTransform::rotation(
+        0.0,
+        0.0,
+        1.0,
+        Angle::radians(2.0 * std::f32::consts::PI * angle),
+    );
+    let center = rect.center();
+    let transform_origin = LayoutVector3D::new(center.x, center.y, 0.0);
+    let transform = rotation
+        .pre_translate(-transform_origin)
+        .then_translate(transform_origin);
+    let spatial_id = builder.push_reference_frame(
+        LayoutPoint::zero(),
+        spatial_id,
+        TransformStyle::Flat,
+        PropertyBinding::Value(transform),
+        ReferenceFrameKind::Transform {
+            is_2d_scale_translation: false,
+            should_snap: false,
+            paired_with_perspective: false,
+        },
+        item_key,
+    );
+    builder.push_rect(
+        &CommonItemProperties::new(
+            rect,
+            SpaceAndClipInfo {
+                spatial_id,
+                clip_chain_id: ClipChainId::INVALID,
+            },
+        ),
+        rect,
+        color,
+    );
+}
+
+fn build_display_list(
+    builder: &mut DisplayListBuilder,
+    scroll_id: ExternalScrollId,
+    root_pipeline_id: PipelineId,
+    layout_size: LayoutSize,
+    time: f32,
+    invalidations: Invalidations,
+) {
+    let size_factor = match invalidations {
+        Invalidations::Small => 0.1,
+        Invalidations::Large | Invalidations::Scrolling => 1.0,
+    };
+
+    let fixed_space_info = SpaceAndClipInfo {
+        spatial_id: SpatialId::root_scroll_node(root_pipeline_id),
+        clip_chain_id: ClipChainId::INVALID,
+    };
+
+    let scroll_spatial_id = builder.define_scroll_frame(
+        fixed_space_info.spatial_id,
+        scroll_id,
+        LayoutRect::from_size(layout_size),
+        LayoutRect::from_size(layout_size),
+        LayoutVector2D::zero(),
+        APZScrollGeneration::default(),
+        HasScrollLinkedEffect::No,
+        SpatialTreeItemKey::new(1, 0),
+    );
+
+    builder.push_rect(
+        &CommonItemProperties::new(
+            LayoutRect::from_size(layout_size).inflate(-10.0, -10.0),
+            fixed_space_info,
+        ),
+        LayoutRect::from_size(layout_size).inflate(-10.0, -10.0),
+        ColorF::new(0.8, 0.8, 0.8, 1.0),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(100.0, 100.0),
+            LayoutSize::new(size_factor * 400.0, size_factor * 400.0),
+        ),
+        ColorF::new(1.0, 0.0, 0.0, 1.0),
+        scroll_spatial_id,
+        root_pipeline_id,
+        time,
+        time,
+        SpatialTreeItemKey::new(1, 1),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(800.0, 100.0),
+            LayoutSize::new(size_factor * 100.0, size_factor * 600.0),
+        ),
+        ColorF::new(0.0, 1.0, 0.0, 1.0),
+        fixed_space_info.spatial_id,
+        root_pipeline_id,
+        0.2,
+        time,
+        SpatialTreeItemKey::new(1, 2),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(700.0, 200.0),
+            LayoutSize::new(size_factor * 300.0, size_factor * 300.0),
+        ),
+        ColorF::new(0.0, 0.0, 1.0, 1.0),
+        scroll_spatial_id,
+        root_pipeline_id,
+        0.1,
+        time,
+        SpatialTreeItemKey::new(1, 3),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(100.0, 600.0),
+            LayoutSize::new(size_factor * 400.0, size_factor * 400.0),
+        ),
+        ColorF::new(1.0, 1.0, 0.0, 1.0),
+        scroll_spatial_id,
+        root_pipeline_id,
+        time,
+        time,
+        SpatialTreeItemKey::new(1, 4),
+    );
+
+    push_rotated_rect(
+        builder,
+        LayoutRect::from_origin_and_size(
+            LayoutPoint::new(700.0, 600.0),
+            LayoutSize::new(size_factor * 400.0, size_factor * 400.0),
+        ),
+        ColorF::new(0.0, 1.0, 1.0, 1.0),
+        scroll_spatial_id,
+        root_pipeline_id,
+        time,
+        time,
+        SpatialTreeItemKey::new(1, 5),
+    );
+}
+
+#[derive(Debug, Copy, Clone)]
+enum Invalidations {
+    Large,
+    Small,
+    Scrolling,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+enum Sync {
+    None = 0,
+    Swap = 1,
+    Commit = 2,
+    Flush = 3,
+    Query = 4,
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() != 6 {
+        println!("USAGE: compositor [native|none] [small|large|scroll] [none|swap|commit|flush|query] width height");
+        process::exit(0);
+    }
+
+    let enable_compositor = match args[1].parse::<String>().unwrap().as_str() {
+        "native" => true,
+        "none" => false,
+        _ => panic!("invalid compositor [native, none]"),
+    };
+
+    let inv_mode = match args[2].parse::<String>().unwrap().as_str() {
+        "small" => Invalidations::Small,
+        "large" => Invalidations::Large,
+        "scroll" => Invalidations::Scrolling,
+        _ => panic!("invalid invalidations [small, large, scroll]"),
+    };
+
+    let sync_mode = match args[3].parse::<String>().unwrap().as_str() {
+        "none" => Sync::None,
+        "swap" => Sync::Swap,
+        "commit" => Sync::Commit,
+        "flush" => Sync::Flush,
+        "query" => Sync::Query,
+        _ => panic!("invalid sync mode [none, swap, commit, flush, query]"),
+    };
+
+    let width = args[4].parse().unwrap();
+    let height = args[5].parse().unwrap();
+    let device_size = DeviceIntSize::new(width, height);
+
+    // Load GL, construct WR and the native compositor interface.
+    let window = compositor::create_window(
+        device_size.width,
+        device_size.height,
+        enable_compositor,
+        sync_mode as i32,
+    );
+    let debug_flags = DebugFlags::empty();
+    let compositor_config = if enable_compositor {
+        webrender::CompositorConfig::Native {
+            compositor: Box::new(DirectCompositeInterface::new(window)),
+        }
+    } else {
+        webrender::CompositorConfig::Draw {
+            max_partial_present_rects: 0,
+            draw_previous_partial_present_regions: false,
+            partial_present: None,
+        }
+    };
+    let opts = webrender::WebRenderOptions {
+        clear_color: ColorF::new(1.0, 1.0, 1.0, 1.0),
+        debug_flags,
+        compositor_config,
+        surface_origin_is_top_left: false,
+        ..webrender::WebRenderOptions::default()
+    };
+    let (tx, rx) = mpsc::channel();
+    let notifier = Box::new(Notifier::new(tx));
+    let gl = unsafe {
+        gl::GlesFns::load_with(|symbol| {
+            let symbol = CString::new(symbol).unwrap();
+            let ptr = compositor::get_proc_address(symbol.as_ptr());
+            ptr
+        })
+    };
+    let (mut renderer, sender) =
+        webrender::create_webrender_instance(gl.clone(), notifier, opts, None).unwrap();
+    let mut api = sender.create_api();
+    let document_id = api.add_document(device_size);
+    let device_pixel_ratio = 1.0;
+    let mut current_epoch = Epoch(0);
+    let root_pipeline_id = PipelineId(0, 0);
+    let layout_size = device_size.to_f32() / euclid::Scale::new(device_pixel_ratio);
+    let mut time = 0.0;
+    let scroll_id = ExternalScrollId(3, root_pipeline_id);
+
+    // Kick off first transaction which will mean we get a notify below to build the DL and render.
+    let mut txn = Transaction::new();
+    txn.set_root_pipeline(root_pipeline_id);
+
+    if let Invalidations::Scrolling = inv_mode {
+        let mut root_builder = DisplayListBuilder::new(root_pipeline_id);
+        root_builder.begin();
+
+        build_display_list(
+            &mut root_builder,
+            scroll_id,
+            root_pipeline_id,
+            layout_size,
+            1.0,
+            inv_mode,
+        );
+
+        txn.set_display_list(current_epoch, root_builder.end());
+    }
+
+    txn.generate_frame(0, RenderReasons::empty());
+    api.send_transaction(document_id, txn);
+
+    // Tick the compositor (in this sample, we don't block on UI events)
+    while compositor::tick(window) {
+        // If there is a new frame ready to draw
+        if let Ok(..) = rx.try_recv() {
+            // Update and render. This will invoke the native compositor interface implemented above
+            // as required.
+            renderer.update();
+            renderer.render(device_size, 0).unwrap();
+            let _ = renderer.flush_pipeline_info();
+
+            // Construct a simple display list that can be drawn and composited by DC.
+            let mut txn = Transaction::new();
+
+            match inv_mode {
+                Invalidations::Small | Invalidations::Large => {
+                    let mut root_builder = DisplayListBuilder::new(root_pipeline_id);
+                    root_builder.begin();
+
+                    build_display_list(
+                        &mut root_builder,
+                        scroll_id,
+                        root_pipeline_id,
+                        layout_size,
+                        time,
+                        inv_mode,
+                    );
+
+                    txn.set_display_list(current_epoch, root_builder.end());
+                }
+                Invalidations::Scrolling => {
+                    let d = 0.5 - 0.5 * (2.0 * f32::consts::PI * 5.0 * time).cos();
+                    txn.set_scroll_offsets(
+                        scroll_id,
+                        vec![SampledScrollOffset {
+                            offset: LayoutVector2D::new(0.0, (d * 100.0).round()),
+                            generation: APZScrollGeneration::default(),
+                        }],
+                    );
+                }
+            }
+
+            txn.generate_frame(0, RenderReasons::empty());
+            api.send_transaction(document_id, txn);
+            current_epoch.0 += 1;
+            time += 0.001;
+            if time > 1.0 {
+                time = 0.0;
+            }
+
+            // This does nothing when native compositor is enabled
+            compositor::swap_buffers(window);
+        }
+    }
+
+    renderer.deinit();
+    compositor::destroy_window(window);
+}