From a338c76bc6569ce4de39a36f576102b0aff3470a Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Fri, 9 Nov 2012 16:35:43 -0800
Subject: [PATCH] gfx: Use pipes to transfer layer buffers between the render
 supervisor function and the render callback

---
 src/servo/gfx/render_layers.rs | 23 +++++++++++++++----
 src/servo/gfx/render_task.rs   | 40 ++++++++++++++++++++--------------
 2 files changed, 43 insertions(+), 20 deletions(-)

diff --git a/src/servo/gfx/render_layers.rs b/src/servo/gfx/render_layers.rs
index fcf49678c16..2a4b0dd380c 100644
--- a/src/servo/gfx/render_layers.rs
+++ b/src/servo/gfx/render_layers.rs
@@ -5,6 +5,7 @@ use opts::Opts;
 use azure::AzFloat;
 use azure::azure_hl::{B8G8R8A8, DrawTarget};
 use core::libc::c_int;
+use core::pipes::Chan;
 use geom::matrix2d::Matrix2D;
 use geom::point::Point2D;
 use geom::rect::Rect;
@@ -17,6 +18,8 @@ pub struct RenderLayer {
     size: Size2D<uint>
 }
 
+type RenderFn = &fn(layer: &RenderLayer, buffer: LayerBuffer, return_buffer: Chan<LayerBuffer>);
+
 /// Given a layer and a buffer, either reuses the buffer (if it's of the right size and format)
 /// or creates a new buffer (if it's not of the appropriate size and format) and invokes the
 /// given callback with the render layer and the buffer. Returns the resulting layer buffer (which
@@ -24,11 +27,11 @@ pub struct RenderLayer {
 pub fn render_layers(layer: &RenderLayer,
                      buffer_set: LayerBufferSet,
                      opts: &Opts,
-                     f: &fn(layer: &RenderLayer, buffer: &LayerBuffer) -> bool) -> LayerBufferSet {
+                     f: RenderFn) -> LayerBufferSet {
     let mut buffers = match move buffer_set { LayerBufferSet { buffers: move b } => move b };
 
     // FIXME: Try not to create a new array here.
-    let new_buffers = dvec::DVec();
+    let new_buffer_ports = dvec::DVec();
 
     // Divide up the layer into tiles.
     let mut y = 0;
@@ -100,14 +103,26 @@ pub fn render_layers(layer: &RenderLayer,
                 };
             //}
 
-            let _ = f(layer, &buffer);
-            new_buffers.push(move buffer);
+            // Create a port and channel pair to receive the new buffer.
+            let (new_buffer_chan, new_buffer_port) = pipes::stream();
+
+            // Send the buffer to the child.
+            f(layer, move buffer, move new_buffer_chan);
+
+            // Enqueue the port.
+            new_buffer_ports.push(move new_buffer_port);
 
             x += TILE_SIZE;
         }
         y += TILE_SIZE;
     }
 
+    debug!("servo::gfx::render_layers: waiting on ports...");
+    let new_buffers = dvec::DVec();
+    for new_buffer_ports.each |new_buffer_port| {
+        new_buffers.push(new_buffer_port.recv());
+    }
+
     return LayerBufferSet { buffers: move dvec::unwrap(move new_buffers) };
 }
 
diff --git a/src/servo/gfx/render_task.rs b/src/servo/gfx/render_task.rs
index 788faa20451..28d60dc9496 100644
--- a/src/servo/gfx/render_task.rs
+++ b/src/servo/gfx/render_task.rs
@@ -87,25 +87,33 @@ impl<C: Compositor Send> Renderer<C> {
             let layer_buffer_set = layer_buffer_set_cell.take();
             let layer_buffer_set_channel = layer_buffer_set_channel_cell.take();
 
-            let layer_buffer_set = for render_layers(&render_layer,
-                                                     move layer_buffer_set,
-                                                     &self.opts)
-                    |render_layer, layer_buffer| {
-                let ctx = RenderContext {
-                    canvas: layer_buffer,
-                    font_ctx: self.font_ctx,
-                    opts: &self.opts
-                };
+            let layer_buffer_set = do render_layers(&render_layer,
+                                                    move layer_buffer_set,
+                                                    &self.opts)
+                    |render_layer, layer_buffer, buffer_chan| {
+                {
+                    // Build the render context.
+                    let ctx = RenderContext {
+                        canvas: &layer_buffer,
+                        font_ctx: self.font_ctx,
+                        opts: &self.opts
+                    };
 
-                // Apply the translation to render the tile we want.
-                let matrix: Matrix2D<AzFloat> = Matrix2D::identity();
-                let matrix = matrix.translate(&-(layer_buffer.rect.origin.x as AzFloat),
-                                              &-(layer_buffer.rect.origin.y as AzFloat));
-                layer_buffer.draw_target.set_transform(&matrix);
+                    // Apply the translation to render the tile we want.
+                    let matrix: Matrix2D<AzFloat> = Matrix2D::identity();
+                    let matrix = matrix.translate(&-(layer_buffer.rect.origin.x as AzFloat),
+                                                  &-(layer_buffer.rect.origin.y as AzFloat));
+                    layer_buffer.draw_target.set_transform(&matrix);
 
-                ctx.clear();
+                    // Clear the buffer.
+                    ctx.clear();
 
-                render_layer.display_list.draw_into_context(&ctx);
+                    // Draw the display list.
+                    render_layer.display_list.draw_into_context(&ctx);
+                }
+
+                // Send back the buffer.
+                buffer_chan.send(move layer_buffer);
             };
 
             #debug("renderer: returning surface");