gfx: Use layer buffer sets instead of a single layer buffer

5 files changed, 87 insertions, 71 deletions

diff --git a/src/servo/gfx/compositor.rs b/src/servo/gfx/compositor.rs
index f434564dd41..f704132dddf 100644
--- a/src/servo/gfx/compositor.rs
+++ b/src/servo/gfx/compositor.rs
@@ -16,12 +16,18 @@ struct LayerBuffer {
     stride: uint
 }
 
+/// A set of layer buffers. This is an atomic unit used to switch between the front and back
+/// buffers.
+struct LayerBufferSet {
+    buffers: ~[LayerBuffer]
+}
+
 /**
 The interface used to by the renderer to aquire draw targets for
 each rendered frame and submit them to be drawn to the display
 */
 trait Compositor {
-    fn begin_drawing(next_dt: pipes::Chan<LayerBuffer>);
-    fn draw(next_dt: pipes::Chan<LayerBuffer>, +draw_me: LayerBuffer);
+    fn begin_drawing(next_dt: pipes::Chan<LayerBufferSet>);
+    fn draw(next_dt: pipes::Chan<LayerBufferSet>, +draw_me: LayerBufferSet);
 }
 
diff --git a/src/servo/gfx/png_compositor.rs b/src/servo/gfx/png_compositor.rs
index 094a4181479..bd0f108feb2 100644
--- a/src/servo/gfx/png_compositor.rs
+++ b/src/servo/gfx/png_compositor.rs
@@ -12,8 +12,8 @@ use azure::azure_hl::DrawTarget;
 use cairo::cairo_hl::ImageSurface;
 use cairo::{CAIRO_FORMAT_ARGB32, cairo_surface_t, cairo_status_t, CAIRO_STATUS_SUCCESS};
 use cairo_bg = cairo::bindgen;
-use cairo_bg::{cairo_image_surface_create, cairo_surface_destroy,
-                  cairo_surface_write_to_png_stream};
+use cairo_bg::{cairo_image_surface_create, cairo_surface_destroy};
+use cairo_bg::{cairo_surface_write_to_png_stream};
 use compositor::Compositor;
 use render_task::{RenderTask, RenderMsg};
 use task::spawn_listener;
@@ -25,23 +25,23 @@ use dvec::DVec;
 use display_list::DisplayList;
 use std::cell::Cell;
 use core::io::BytesWriter;
-use gfx::compositor::LayerBuffer;
+use gfx::compositor::{LayerBuffer, LayerBufferSet};
 use geom::size::Size2D;
 use gfx::render_layers::RenderLayer;
 
 pub type PngCompositor = Chan<Msg>;
 
 pub enum Msg {
-    BeginDrawing(pipes::Chan<LayerBuffer>),
-    Draw(pipes::Chan<LayerBuffer>, LayerBuffer),
+    BeginDrawing(pipes::Chan<LayerBufferSet>),
+    Draw(pipes::Chan<LayerBufferSet>, LayerBufferSet),
     Exit
 }
 
 impl Chan<Msg> : Compositor {
-    fn begin_drawing(next_dt: pipes::Chan<LayerBuffer>) {
+    fn begin_drawing(next_dt: pipes::Chan<LayerBufferSet>) {
         self.send(BeginDrawing(move next_dt))
     }
-    fn draw(next_dt: pipes::Chan<LayerBuffer>, draw_me: LayerBuffer) {
+    fn draw(next_dt: pipes::Chan<LayerBufferSet>, draw_me: LayerBufferSet) {
         self.send(Draw(move next_dt, move draw_me))
     }
 }
@@ -56,17 +56,18 @@ pub fn PngCompositor(output: Chan<~[u8]>) -> PngCompositor {
             size: Size2D(800u, 600u),
             stride: 800
         };
-        let layer_buffer = Cell(move layer_buffer);
+        let layer_buffer_set = LayerBufferSet { buffers: ~[ move layer_buffer ] };
+        let layer_buffer_set = Cell(move layer_buffer_set);
 
         loop {
             match po.recv() {
                 BeginDrawing(sender) => {
                     debug!("png_compositor: begin_drawing");
-                    sender.send(layer_buffer.take());
+                    sender.send(layer_buffer_set.take());
                 }
-                Draw(move sender, move layer_buffer) => {
+                Draw(move sender, move layer_buffer_set) => {
                     debug!("png_compositor: draw");
-                    do_draw(move sender, move layer_buffer, output, &cairo_surface);
+                    do_draw(move sender, move layer_buffer_set, output, &cairo_surface);
                 }
                 Exit => break
             }
@@ -74,8 +75,8 @@ pub fn PngCompositor(output: Chan<~[u8]>) -> PngCompositor {
     }
 }
 
-fn do_draw(sender: pipes::Chan<LayerBuffer>,
-           layer_buffer: LayerBuffer,
+fn do_draw(sender: pipes::Chan<LayerBufferSet>,
+           layer_buffer_set: LayerBufferSet,
            output: Chan<~[u8]>,
            cairo_surface: &ImageSurface) {
     let buffer = BytesWriter();
@@ -83,7 +84,7 @@ fn do_draw(sender: pipes::Chan<LayerBuffer>,
     output.send(buffer.bytes.get());
 
     // Send the next draw target to the renderer
-    sender.send(move layer_buffer);
+    sender.send(move layer_buffer_set);
 }
 
 #[test]
diff --git a/src/servo/gfx/render_layers.rs b/src/servo/gfx/render_layers.rs
index bd24bcd813c..8d155a23cea 100644
--- a/src/servo/gfx/render_layers.rs
+++ b/src/servo/gfx/render_layers.rs
@@ -1,5 +1,5 @@
 use gfx::display_list::DisplayList;
-use gfx::compositor::LayerBuffer;
+use gfx::compositor::{LayerBuffer, LayerBufferSet};
 
 use azure::azure_hl::DrawTarget;
 use cairo::CAIRO_FORMAT_RGB24;
@@ -17,9 +17,10 @@ pub struct RenderLayer {
 /// given callback with the render layer and the buffer. Returns the resulting layer buffer (which
 /// might be the old layer buffer if it had the appropriate size and format).
 pub fn render_layers(layer: &RenderLayer,
-                     buffer: LayerBuffer,
-                     f: &fn(layer: &RenderLayer, buffer: &LayerBuffer) -> bool) -> LayerBuffer {
-    let mut buffer = move buffer;
+                     buffer_set: LayerBufferSet,
+                     f: &fn(layer: &RenderLayer, buffer: &LayerBuffer) -> bool) -> LayerBufferSet {
+    let mut buffers = match move buffer_set { LayerBufferSet { buffers: move b } => move b };
+    let mut buffer = buffers.pop();
     if buffer.size != layer.size {
         // Create a new buffer.
 
@@ -44,6 +45,6 @@ pub fn render_layers(layer: &RenderLayer,
     }
 
     let _ = f(layer, &buffer);
-    return move buffer;
+    return LayerBufferSet { buffers: ~[ move buffer ] };
 }
 
diff --git a/src/servo/gfx/render_task.rs b/src/servo/gfx/render_task.rs
index d762ffbf2ce..52ab43717e4 100644
--- a/src/servo/gfx/render_task.rs
+++ b/src/servo/gfx/render_task.rs
@@ -1,7 +1,7 @@
 use au = gfx::geometry;
 use au::Au;
 use comm::*;
-use compositor::{Compositor, LayerBuffer};
+use compositor::{Compositor, LayerBufferSet};
 use dl = display_list;
 use mod gfx::render_layers;
 use render_layers::render_layers;
@@ -24,7 +24,7 @@ pub type RenderTask = comm::Chan<Msg>;
 pub fn RenderTask<C: Compositor Send>(compositor: C) -> RenderTask {
     let compositor_cell = Cell(move compositor);
     do task::spawn_listener |po: comm::Port<Msg>, move compositor_cell| {
-        let (layer_buffer_channel, layer_buffer_port) = pipes::stream();
+        let (layer_buffer_channel, layer_buffer_set_port) = pipes::stream();
 
         let compositor = compositor_cell.take();
         compositor.begin_drawing(move layer_buffer_channel);
@@ -32,7 +32,7 @@ pub fn RenderTask<C: Compositor Send>(compositor: C) -> RenderTask {
         Renderer {
             port: po,
             compositor: move compositor,
-            mut layer_buffer_port: Cell(move layer_buffer_port),
+            mut layer_buffer_set_port: Cell(move layer_buffer_set_port),
             font_cache: FontCache(),
         }.start();
     }
@@ -41,7 +41,7 @@ pub fn RenderTask<C: Compositor Send>(compositor: C) -> RenderTask {
 priv struct Renderer<C: Compositor Send> {
     port: comm::Port<Msg>,
     compositor: C,
-    layer_buffer_port: Cell<pipes::Port<LayerBuffer>>,
+    layer_buffer_set_port: Cell<pipes::Port<LayerBufferSet>>,
     font_cache: @FontCache
 }
 
@@ -63,28 +63,28 @@ impl<C: Compositor Send> Renderer<C> {
     fn render(render_layer: RenderLayer) {
         debug!("renderer: got render request");
 
-        let layer_buffer_port = self.layer_buffer_port.take();
+        let layer_buffer_set_port = self.layer_buffer_set_port.take();
 
-        if !layer_buffer_port.peek() {
+        if !layer_buffer_set_port.peek() {
             warn!("renderer: waiting on layer buffer");
         }
 
-        let layer_buffer = layer_buffer_port.recv();
-        let (layer_buffer_channel, new_layer_buffer_port) = pipes::stream();
-        self.layer_buffer_port.put_back(move new_layer_buffer_port);
+        let layer_buffer_set = layer_buffer_set_port.recv();
+        let (layer_buffer_set_channel, new_layer_buffer_set_port) = pipes::stream();
+        self.layer_buffer_set_port.put_back(move new_layer_buffer_set_port);
 
         let render_layer_cell = Cell(move render_layer);
-        let layer_buffer_cell = Cell(move layer_buffer);
-        let layer_buffer_channel_cell = Cell(move layer_buffer_channel);
+        let layer_buffer_set_cell = Cell(move layer_buffer_set);
+        let layer_buffer_set_channel_cell = Cell(move layer_buffer_set_channel);
 
         #debug("renderer: rendering");
 
         do util::time::time(~"rendering") {
             let render_layer = render_layer_cell.take();
-            let layer_buffer = layer_buffer_cell.take();
-            let layer_buffer_channel = layer_buffer_channel_cell.take();
+            let layer_buffer_set = layer_buffer_set_cell.take();
+            let layer_buffer_set_channel = layer_buffer_set_channel_cell.take();
 
-            let layer_buffer = for render_layers(&render_layer, move layer_buffer)
+            let layer_buffer_set = for render_layers(&render_layer, move layer_buffer_set)
                     |render_layer, layer_buffer| {
                 let ctx = RenderContext {
                     canvas: layer_buffer,
@@ -96,7 +96,7 @@ impl<C: Compositor Send> Renderer<C> {
             };
 
             #debug("renderer: returning surface");
-            self.compositor.draw(move layer_buffer_channel, move layer_buffer);
+            self.compositor.draw(move layer_buffer_set_channel, move layer_buffer_set);
         }
     }
 }
diff --git a/src/servo/platform/osmain.rs b/src/servo/platform/osmain.rs
index 167d51d4def..0db894cdf05 100644
--- a/src/servo/platform/osmain.rs
+++ b/src/servo/platform/osmain.rs
@@ -1,20 +1,21 @@
-use mod azure::azure_hl;
+use ShareGlContext = sharegl::platform::Context;
+use azure::azure_hl;
 use azure::azure_hl::DrawTarget;
-use cairo::cairo_surface_t;
 use cairo::cairo_hl::ImageSurface;
-use dvec::DVec;
-use gfx::compositor::{LayerBuffer, Compositor};
+use cairo::cairo_surface_t;
+use core::util::replace;
 use dom::event::{Event, ResizeEvent};
-use layers::ImageLayer;
+use dvec::DVec;
 use geom::matrix::{Matrix4, identity};
 use geom::size::Size2D;
-use ShareGlContext = sharegl::platform::Context;
+use gfx::compositor::{Compositor, LayerBuffer, LayerBufferSet};
+use layers::ImageLayer;
+use pipes::Chan;
+use resize_rate_limiter::ResizeRateLimiter;
+use std::cell::Cell;
 use std::cmp::FuzzyEq;
 use task::TaskBuilder;
 use vec::push;
-use pipes::Chan;
-use std::cell::Cell;
-use resize_rate_limiter::ResizeRateLimiter;
 
 pub type OSMain = comm::Chan<Msg>;
 
@@ -30,8 +31,8 @@ enum Window {
 }
 
 pub enum Msg {
-    BeginDrawing(pipes::Chan<LayerBuffer>),
-    Draw(pipes::Chan<LayerBuffer>, LayerBuffer),
+    BeginDrawing(pipes::Chan<LayerBufferSet>),
+    Draw(pipes::Chan<LayerBufferSet>, LayerBufferSet),
     AddKeyHandler(pipes::Chan<()>),
     Exit
 }
@@ -120,11 +121,12 @@ fn mainloop(mode: Mode, po: comm::Port<Msg>, dom_event_chan: pipes::SharedChan<E
                     return_surface(surfaces, move dt);
                     lend_surface(surfaces, move sender);
 
-                    let width = surfaces.front.layer_buffer.size.width as uint;
-                    let height = surfaces.front.layer_buffer.size.height as uint;
+                    let buffers = &mut surfaces.front.layer_buffer_set.buffers;
+                    let width = buffers[0].size.width as uint;
+                    let height = buffers[0].size.height as uint;
 
                     let image_data = @CairoSurfaceImageData {
-                        cairo_surface: surfaces.front.layer_buffer.cairo_surface.clone(),
+                        cairo_surface: buffers[0].cairo_surface.clone(),
                         size: Size2D(width, height)
                     };
                     let image = @layers::layers::Image::new(
@@ -142,7 +144,6 @@ fn mainloop(mode: Mode, po: comm::Port<Msg>, dom_event_chan: pipes::SharedChan<E
     };
 
     let adjust_for_window_resizing: fn@() = || {
-        let height = surfaces.front.layer_buffer.size.height as uint;
         let window_width = glut::get(glut::WindowWidth) as uint;
         let window_height = glut::get(glut::WindowHeight) as uint;
 
@@ -167,15 +168,14 @@ fn mainloop(mode: Mode, po: comm::Port<Msg>, dom_event_chan: pipes::SharedChan<E
     match window {
         GlutWindow(window) => {
             do glut::reshape_func(window) |width, height| {
-                check_for_messages();
-
                 #debug("osmain: window resized to %d,%d", width as int, height as int);
+                check_for_messages();
                 resize_rate_limiter.window_resized(width as uint, height as uint);
-
-                composite();
+                //composite();
             }
 
             do glut::display_func() {
+                debug!("osmain: display func");
                 check_for_messages();
                 composite();
             }
@@ -203,10 +203,10 @@ Implementation to allow the osmain channel to be used as a graphics
 compositor for the renderer
 */
 impl OSMain : Compositor {
-    fn begin_drawing(next_dt: pipes::Chan<LayerBuffer>) {
+    fn begin_drawing(next_dt: pipes::Chan<LayerBufferSet>) {
         self.send(BeginDrawing(move next_dt))
     }
-    fn draw(next_dt: pipes::Chan<LayerBuffer>, draw_me: LayerBuffer) {
+    fn draw(next_dt: pipes::Chan<LayerBufferSet>, draw_me: LayerBufferSet) {
         self.send(Draw(move next_dt, move draw_me))
     }
 }
@@ -216,19 +216,26 @@ struct SurfaceSet {
     mut back: Surface,
 }
 
-fn lend_surface(surfaces: &SurfaceSet, receiver: pipes::Chan<LayerBuffer>) {
+fn lend_surface(surfaces: &SurfaceSet, receiver: pipes::Chan<LayerBufferSet>) {
     // We are in a position to lend out the surface?
     assert surfaces.front.have;
     // Ok then take it
-    let draw_target_ref = &mut surfaces.front.layer_buffer.draw_target;
-    let layer_buffer = LayerBuffer {
-        cairo_surface: surfaces.front.layer_buffer.cairo_surface.clone(),
-        draw_target: azure_hl::clone_mutable_draw_target(draw_target_ref),
-        size: copy surfaces.front.layer_buffer.size,
-        stride: surfaces.front.layer_buffer.stride
+    let old_layer_buffers = replace(&mut surfaces.front.layer_buffer_set.buffers, ~[]);
+    let new_layer_buffers = do old_layer_buffers.map |layer_buffer| {
+        let draw_target_ref = &layer_buffer.draw_target;
+        let layer_buffer = LayerBuffer {
+            cairo_surface: layer_buffer.cairo_surface.clone(),
+            draw_target: draw_target_ref.clone(),
+            size: copy layer_buffer.size,
+            stride: layer_buffer.stride
+        };
+        #debug("osmain: lending surface %?", layer_buffer);
+        move layer_buffer
     };
-    #debug("osmain: lending surface %?", layer_buffer);
-    receiver.send(move layer_buffer);
+    surfaces.front.layer_buffer_set.buffers = move old_layer_buffers;
+
+    let new_layer_buffer_set = LayerBufferSet { buffers: move new_layer_buffers };
+    receiver.send(move new_layer_buffer_set);
     // Now we don't have it
     surfaces.front.have = false;
     // But we (hopefully) have another!
@@ -237,13 +244,13 @@ fn lend_surface(surfaces: &SurfaceSet, receiver: pipes::Chan<LayerBuffer>) {
     assert surfaces.front.have;
 }
 
-fn return_surface(surfaces: &SurfaceSet, layer_buffer: LayerBuffer) {
-    #debug("osmain: returning surface %?", layer_buffer);
+fn return_surface(surfaces: &SurfaceSet, layer_buffer_set: LayerBufferSet) {
+    #debug("osmain: returning surface %?", layer_buffer_set);
     // We have room for a return
     assert surfaces.front.have;
     assert !surfaces.back.have;
 
-    surfaces.back.layer_buffer = move layer_buffer;
+    surfaces.back.layer_buffer_set = move layer_buffer_set;
 
     // Now we have it again
     surfaces.back.have = true;
@@ -254,7 +261,7 @@ fn SurfaceSet() -> SurfaceSet {
 }
 
 struct Surface {
-    layer_buffer: LayerBuffer,
+    layer_buffer_set: LayerBufferSet,
     mut have: bool,
 }
 
@@ -267,7 +274,8 @@ fn Surface() -> Surface {
         size: Size2D(800u, 600u),
         stride: 800
     };
-    Surface { layer_buffer: move layer_buffer, have: true }
+    let layer_buffer_set = LayerBufferSet { buffers: ~[ move layer_buffer ] };
+    Surface { layer_buffer_set: move layer_buffer_set, have: true }
 }
 
 /// A function for spawning into the platform's main thread