1 files changed, 326 insertions, 0 deletions
diff --git a/gfx/wr/webrender/src/renderer/gpu_buffer.rs b/gfx/wr/webrender/src/renderer/gpu_buffer.rs
new file mode 100644
index 0000000000..05543d51ee
--- /dev/null
+++ b/gfx/wr/webrender/src/renderer/gpu_buffer.rs
@@ -0,0 +1,326 @@
+/* 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/. */
+
+/*
+
+    TODO:
+        Recycle GpuBuffers in a pool (support return from render thread)
+        Efficiently allow writing to buffer (better push interface)
+        Support other texel types (e.g. i32)
+
+ */
+
+use crate::renderer::MAX_VERTEX_TEXTURE_WIDTH;
+use api::units::{DeviceIntRect, DeviceIntSize, LayoutRect, PictureRect, DeviceRect};
+use api::{PremultipliedColorF};
+use crate::device::Texel;
+use crate::render_task_graph::{RenderTaskGraph, RenderTaskId};
+
+
+unsafe impl Texel for GpuBufferBlock {}
+
+/// A single texel in RGBAF32 texture - 16 bytes.
+#[derive(Copy, Clone, Debug, MallocSizeOf)]
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+pub struct GpuBufferBlock {
+    data: [f32; 4],
+}
+
+#[derive(Copy, Debug, Clone, MallocSizeOf, Eq, PartialEq)]
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+pub struct GpuBufferAddress {
+    pub u: u16,
+    pub v: u16,
+}
+
+impl GpuBufferAddress {
+    #[allow(dead_code)]
+    pub fn as_int(self) -> i32 {
+        // TODO(gw): Temporarily encode GPU Cache addresses as a single int.
+        //           In the future, we can change the PrimitiveInstanceData struct
+        //           to use 2x u16 for the vertex attribute instead of an i32.
+        self.v as i32 * MAX_VERTEX_TEXTURE_WIDTH as i32 + self.u as i32
+    }
+}
+
+impl GpuBufferBlock {
+    pub const EMPTY: Self = GpuBufferBlock { data: [0.0; 4] };
+}
+
+impl Into<GpuBufferBlock> for LayoutRect {
+    fn into(self) -> GpuBufferBlock {
+        GpuBufferBlock {
+            data: [
+                self.min.x,
+                self.min.y,
+                self.max.x,
+                self.max.y,
+            ],
+        }
+    }
+}
+
+impl Into<GpuBufferBlock> for PictureRect {
+    fn into(self) -> GpuBufferBlock {
+        GpuBufferBlock {
+            data: [
+                self.min.x,
+                self.min.y,
+                self.max.x,
+                self.max.y,
+            ],
+        }
+    }
+}
+
+impl Into<GpuBufferBlock> for DeviceRect {
+    fn into(self) -> GpuBufferBlock {
+        GpuBufferBlock {
+            data: [
+                self.min.x,
+                self.min.y,
+                self.max.x,
+                self.max.y,
+            ],
+        }
+    }
+}
+
+impl Into<GpuBufferBlock> for PremultipliedColorF {
+    fn into(self) -> GpuBufferBlock {
+        GpuBufferBlock {
+            data: [
+                self.r,
+                self.g,
+                self.b,
+                self.a,
+            ],
+        }
+    }
+}
+
+impl Into<GpuBufferBlock> for DeviceIntRect {
+    fn into(self) -> GpuBufferBlock {
+        GpuBufferBlock {
+            data: [
+                self.min.x as f32,
+                self.min.y as f32,
+                self.max.x as f32,
+                self.max.y as f32,
+            ],
+        }
+    }
+}
+
+impl Into<GpuBufferBlock> for [f32; 4] {
+    fn into(self) -> GpuBufferBlock {
+        GpuBufferBlock {
+            data: self,
+        }
+    }
+}
+
+/// Record a patch to the GPU buffer for a render task
+struct DeferredBlock {
+    task_id: RenderTaskId,
+    index: usize,
+}
+
+/// Interface to allow writing multiple GPU blocks, possibly of different types
+pub struct GpuBufferWriter<'a> {
+    buffer: &'a mut Vec<GpuBufferBlock>,
+    deferred: &'a mut Vec<DeferredBlock>,
+    index: usize,
+    block_count: usize,
+}
+
+impl<'a> GpuBufferWriter<'a> {
+    fn new(
+        buffer: &'a mut Vec<GpuBufferBlock>,
+        deferred: &'a mut Vec<DeferredBlock>,
+        index: usize,
+        block_count: usize,
+    ) -> Self {
+        GpuBufferWriter {
+            buffer,
+            deferred,
+            index,
+            block_count,
+        }
+    }
+
+    /// Push one (16 byte) block of data in to the writer
+    pub fn push_one<B>(&mut self, block: B) where B: Into<GpuBufferBlock> {
+        self.buffer.push(block.into());
+    }
+
+    /// Push a reference to a render task in to the writer. Once the render
+    /// task graph is resolved, this will be patched with the UV rect of the task
+    pub fn push_render_task(&mut self, task_id: RenderTaskId) {
+        self.deferred.push(DeferredBlock {
+            task_id,
+            index: self.buffer.len(),
+        });
+        self.buffer.push(GpuBufferBlock::EMPTY);
+    }
+
+    /// Close this writer, returning the GPU address of this set of block(s).
+    pub fn finish(self) -> GpuBufferAddress {
+        assert_eq!(self.buffer.len(), self.index + self.block_count);
+
+        GpuBufferAddress {
+            u: (self.index % MAX_VERTEX_TEXTURE_WIDTH) as u16,
+            v: (self.index / MAX_VERTEX_TEXTURE_WIDTH) as u16,
+        }
+    }
+}
+
+impl<'a> Drop for GpuBufferWriter<'a> {
+    fn drop(&mut self) {
+        assert_eq!(self.buffer.len(), self.index + self.block_count, "Claimed block_count was not written");
+    }
+}
+
+pub struct GpuBufferBuilder {
+    data: Vec<GpuBufferBlock>,
+    deferred: Vec<DeferredBlock>,
+}
+
+impl GpuBufferBuilder {
+    pub fn new() -> Self {
+        GpuBufferBuilder {
+            data: Vec::new(),
+            deferred: Vec::new(),
+        }
+    }
+
+    #[allow(dead_code)]
+    pub fn push(
+        &mut self,
+        blocks: &[GpuBufferBlock],
+    ) -> GpuBufferAddress {
+        assert!(blocks.len() <= MAX_VERTEX_TEXTURE_WIDTH);
+
+        if (self.data.len() % MAX_VERTEX_TEXTURE_WIDTH) + blocks.len() > MAX_VERTEX_TEXTURE_WIDTH {
+            while self.data.len() % MAX_VERTEX_TEXTURE_WIDTH != 0 {
+                self.data.push(GpuBufferBlock::EMPTY);
+            }
+        }
+
+        let index = self.data.len();
+
+        self.data.extend_from_slice(blocks);
+
+        GpuBufferAddress {
+            u: (index % MAX_VERTEX_TEXTURE_WIDTH) as u16,
+            v: (index / MAX_VERTEX_TEXTURE_WIDTH) as u16,
+        }
+    }
+
+    /// Begin writing a specific number of blocks
+    pub fn write_blocks(
+        &mut self,
+        block_count: usize,
+    ) -> GpuBufferWriter {
+        assert!(block_count <= MAX_VERTEX_TEXTURE_WIDTH);
+
+        if (self.data.len() % MAX_VERTEX_TEXTURE_WIDTH) + block_count > MAX_VERTEX_TEXTURE_WIDTH {
+            while self.data.len() % MAX_VERTEX_TEXTURE_WIDTH != 0 {
+                self.data.push(GpuBufferBlock::EMPTY);
+            }
+        }
+
+        let index = self.data.len();
+
+        GpuBufferWriter::new(
+            &mut self.data,
+            &mut self.deferred,
+            index,
+            block_count,
+        )
+    }
+
+    pub fn finalize(
+        mut self,
+        render_tasks: &RenderTaskGraph,
+    ) -> GpuBuffer {
+        let required_len = (self.data.len() + MAX_VERTEX_TEXTURE_WIDTH-1) & !(MAX_VERTEX_TEXTURE_WIDTH-1);
+
+        for _ in 0 .. required_len - self.data.len() {
+            self.data.push(GpuBufferBlock::EMPTY);
+        }
+
+        let len = self.data.len();
+        assert!(len % MAX_VERTEX_TEXTURE_WIDTH == 0);
+
+        // At this point, we know that the render task graph has been built, and we can
+        // query the location of any dynamic (render target) or static (texture cache)
+        // task. This allows us to patch the UV rects in to the GPU buffer before upload
+        // to the GPU.
+        for block in self.deferred.drain(..) {
+            let render_task = &render_tasks[block.task_id];
+            let target_rect = render_task.get_target_rect();
+            self.data[block.index] = target_rect.into();
+        }
+
+        GpuBuffer {
+            data: self.data,
+            size: DeviceIntSize::new(MAX_VERTEX_TEXTURE_WIDTH as i32, (len / MAX_VERTEX_TEXTURE_WIDTH) as i32),
+        }
+    }
+}
+
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+pub struct GpuBuffer {
+    pub data: Vec<GpuBufferBlock>,
+    pub size: DeviceIntSize,
+}
+
+impl GpuBuffer {
+    pub fn is_empty(&self) -> bool {
+        self.data.is_empty()
+    }
+}
+
+
+#[test]
+fn test_gpu_buffer_sizing_push() {
+    let render_task_graph = RenderTaskGraph::new_for_testing();
+    let mut builder = GpuBufferBuilder::new();
+
+    let row = vec![GpuBufferBlock::EMPTY; MAX_VERTEX_TEXTURE_WIDTH];
+    builder.push(&row);
+
+    builder.push(&[GpuBufferBlock::EMPTY]);
+    builder.push(&[GpuBufferBlock::EMPTY]);
+
+    let buffer = builder.finalize(&render_task_graph);
+    assert_eq!(buffer.data.len(), MAX_VERTEX_TEXTURE_WIDTH * 2);
+}
+
+#[test]
+fn test_gpu_buffer_sizing_writer() {
+    let render_task_graph = RenderTaskGraph::new_for_testing();
+    let mut builder = GpuBufferBuilder::new();
+
+    let mut writer = builder.write_blocks(MAX_VERTEX_TEXTURE_WIDTH);
+    for _ in 0 .. MAX_VERTEX_TEXTURE_WIDTH {
+        writer.push_one(GpuBufferBlock::EMPTY);
+    }
+    writer.finish();
+
+    let mut writer = builder.write_blocks(1);
+    writer.push_one(GpuBufferBlock::EMPTY);
+    writer.finish();
+
+    let mut writer = builder.write_blocks(1);
+    writer.push_one(GpuBufferBlock::EMPTY);
+    writer.finish();
+
+    let buffer = builder.finalize(&render_task_graph);
+    assert_eq!(buffer.data.len(), MAX_VERTEX_TEXTURE_WIDTH * 2);
+}