Implement progressive rendering

4 files changed, 321 insertions, 85 deletions

diff --git a/src/components/gfx/render_task.rs b/src/components/gfx/render_task.rs
index 05cbd0bc079..1fdbc91aa74 100644
--- a/src/components/gfx/render_task.rs
+++ b/src/components/gfx/render_task.rs
@@ -33,7 +33,7 @@ pub struct RenderLayer {
 
 pub enum Msg {
     RenderMsg(RenderLayer),
-    ReRenderMsg(f32),
+    ReRenderMsg(~Rect<uint>], f32),
     PaintPermissionGranted,
     PaintPermissionRevoked,
     ExitMsg(Chan<()>),
@@ -119,11 +119,11 @@ impl<C: RenderListener + Send> RenderTask<C> {
         loop {
             match self.port.recv() {
                 RenderMsg(render_layer) => {
+                    self.compositor.new_layer(render_layer.size, self.opts.tile_size);
                     self.render_layer = Some(render_layer);
-                    self.render(1.0);
                 }
-                ReRenderMsg(scale) => {
-                    self.render(scale);
+                ReRenderMsg(tiles, scale) => {
+                    self.render(tiles, scale);
                 }
                 PaintPermissionGranted => {
                     self.paint_permission = true;
@@ -146,15 +146,15 @@ impl<C: RenderListener + Send> RenderTask<C> {
         }
     }
 
-    fn render(&mut self, scale: f32) {
+    fn render(&mut self, tiles: ~[Rect<uint>], scale: f32) {
         debug!("render_task: rendering");
         
         let render_layer;
-        match (self.render_layer) {
-            None => return,
+        match self.render_layer {
             Some(ref r_layer) => {
                 render_layer = r_layer;
             }
+            _ => return, // nothing to do
         }
 
         self.compositor.set_render_state(RenderingRenderState);
@@ -166,63 +166,56 @@ impl<C: RenderListener + Send> RenderTask<C> {
 
             // Divide up the layer into tiles.
             do time::profile(time::RenderingPrepBuffCategory, self.profiler_chan.clone()) {
-                let mut y = 0;
-                while y < (render_layer.size.height as f32 * scale).ceil() as uint {
-                    let mut x = 0;
-                    while x < (render_layer.size.width as f32 * scale).ceil() as uint {
-                        // Figure out the dimension of this tile.
-                        let right = uint::min(x + tile_size, (render_layer.size.width as f32 * scale).ceil() as uint);
-                        let bottom = uint::min(y + tile_size, (render_layer.size.height as f32 * scale).ceil() as uint);
-                        let width = right - x;
-                        let height = bottom - y;
-
-                        let tile_rect = Rect(Point2D(x as f32 / scale, y as f32 / scale), Size2D(width as f32, height as f32));
-                        let screen_rect = Rect(Point2D(x, y), Size2D(width, height));
-
-                        let buffer = LayerBuffer {
-                            draw_target: DrawTarget::new_with_fbo(self.opts.render_backend,
-                                                                  self.share_gl_context,
-                                                                  Size2D(width as i32,
-                                                                         height as i32),
-                                                                  B8G8R8A8),
-                            rect: tile_rect,
-                            screen_pos: screen_rect,
-                            stride: (width * 4) as uint
+                for tiles.each |tile_rect| {
+                    let x = tile_rect.origin.x;
+                    let y = tile_rect.origin.y;
+                    let width = tile_rect.size.width;
+                    let height = tile_rect.size.height;
+                    
+                    let rect = Rect(Point2D(x as f32 / scale, y as f32 / scale), Size2D(width as f32, height as f32));
+                    
+                    let buffer = LayerBuffer {
+                        draw_target: DrawTarget::new_with_fbo(self.opts.render_backend,
+                                                              self.share_gl_context,
+                                                              Size2D(width as i32, height as i32),
+                                                              B8G8R8A8),
+                        rect: rect,
+                        screen_pos: *tile_rect,
+                        resolution: scale,
+                        stride: (width * 4) as uint
+                    };
+                    
+                    
+                    {
+                        // Build the render context.
+                        let ctx = RenderContext {
+                            canvas: &buffer,
+                            font_ctx: self.font_ctx,
+                            opts: &self.opts
                         };
-
-                        {
-                            // Build the render context.
-                            let ctx = RenderContext {
-                                canvas: &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.scale(scale as AzFloat, scale as AzFloat);
-                            let matrix = matrix.translate(-(buffer.rect.origin.x) as AzFloat,
-                                                          -(buffer.rect.origin.y) as AzFloat);
-
-                            ctx.canvas.draw_target.set_transform(&matrix);
-
-                            // Clear the buffer.
-                            ctx.clear();
-
-                            // Draw the display list.
-                            do profile(time::RenderingDrawingCategory, self.profiler_chan.clone()) {
-                                render_layer.display_list.draw_into_context(&ctx);
-                                ctx.canvas.draw_target.flush();
-                            }
+                        
+                        // Apply the translation to render the tile we want.
+                        let matrix: Matrix2D<AzFloat> = Matrix2D::identity();
+                        let matrix = matrix.scale(scale as AzFloat, scale as AzFloat);
+                        let matrix = matrix.translate(-(buffer.rect.origin.x) as AzFloat,
+                                                      -(buffer.rect.origin.y) as AzFloat);
+                        
+                        ctx.canvas.draw_target.set_transform(&matrix);
+                        
+                        // Clear the buffer.
+                        ctx.clear();
+                        
+                        // Draw the display list.
+                        do profile(time::RenderingDrawingCategory, self.profiler_chan.clone()) {
+                            render_layer.display_list.draw_into_context(&ctx);
+                            ctx.canvas.draw_target.flush();
                         }
-
-                        new_buffers.push(buffer);
-
-                        x += tile_size;
                     }
-
-                    y += tile_size;
+                    
+                    new_buffers.push(buffer);
+                    
                 }
+
             }
 
             let layer_buffer_set = LayerBufferSet {
diff --git a/src/components/main/compositing/mod.rs b/src/components/main/compositing/mod.rs
index 2dc4794a420..efb089e92e6 100644
--- a/src/components/main/compositing/mod.rs
+++ b/src/components/main/compositing/mod.rs
@@ -10,7 +10,7 @@ use windowing::{ApplicationMethods, WindowMethods, WindowMouseEvent, WindowClick
 use windowing::{WindowMouseDownEvent, WindowMouseUpEvent};
 
 
-use servo_msg::compositor_msg::{RenderListener, LayerBufferSet, RenderState};
+use servo_msg::compositor_msg::{RenderListener, LayerBuffer, LayerBufferSet, RenderState};
 use servo_msg::compositor_msg::{ReadyState, ScriptListener};
 use servo_msg::constellation_msg::{CompositorAck, ConstellationChan};
 use servo_msg::constellation_msg;
@@ -28,6 +28,7 @@ use extra::timer;
 use geom::matrix::identity;
 use geom::point::Point2D;
 use geom::size::Size2D;
+use geom::rect::Rect; //eschweic
 use layers::layers::{ARGB32Format, ContainerLayer, ContainerLayerKind, Format};
 use layers::layers::{ImageData, WithDataFn};
 use layers::layers::{TextureLayerKind, TextureLayer, TextureManager};
@@ -40,6 +41,10 @@ use servo_util::time::ProfilerChan;
 use extra::arc;
 pub use windowing;
 
+//eschweic
+use compositing::quadtree::Quadtree;
+mod quadtree;
+
 /// The implementation of the layers-based compositor.
 #[deriving(Clone)]
 pub struct CompositorChan {
@@ -70,6 +75,17 @@ impl RenderListener for CompositorChan {
         self.chan.send(Paint(id, layer_buffer_set, new_size))
     }
 
+    //eschweic
+    fn new_layer(&self, page_size: Size2D<uint>, tile_size: uint) {
+        self.chan.send(NewLayer(page_size, tile_size))
+    }
+    fn resize_layer(&self, page_size: Size2D<uint>) {
+        self.chan.send(ResizeLayer(page_size))
+    }
+    fn delete_layer(&self) {
+        self.chan.send(DeleteLayer)
+    }
+
     fn set_render_state(&self, render_state: RenderState) {
         self.chan.send(ChangeRenderState(render_state))
     }
@@ -102,6 +118,16 @@ pub enum Msg {
     GetSize(Chan<Size2D<int>>),
     /// Requests the compositors GL context.
     GetGLContext(Chan<AzGLContext>),
+
+    //eschweic
+    // FIXME: Attach layer ids and epochs to these messages
+    /// Alerts the compositor that there is a new layer to be rendered.
+    NewLayer(Size2D<uint>, uint),
+    /// Alerts the compositor that the current layer has changed size.
+    ResizeLayer(Size2D<uint>),
+    /// Alerts the compositor that the current layer has been deleted.
+    DeleteLayer,
+
     /// Requests that the compositor paint the given layer buffer set for the given page size.
     Paint(uint, arc::ARC<LayerBufferSet>, Size2D<uint>),
     /// Alerts the compositor to the current status of page loading.
@@ -199,9 +225,61 @@ impl CompositorTask {
         let local_zoom = @mut 1f32;
         // Channel to the current renderer.
         // FIXME: This probably shouldn't be stored like this.
+
         let render_chan: @mut Option<RenderChan> = @mut None;
         let pipeline_id: @mut Option<uint> = @mut None;
 
+        // Quadtree for this layer
+        // FIXME: This should be one-per-layer
+        let quadtree: @mut Option<Quadtree<LayerBuffer>> = @mut None;
+        
+
+        let ask_for_tiles: @fn() = || {
+            match *quadtree {
+                Some(ref quad) => {
+                    let mut tile_size = quad.get_tile_size(); // temporary solution
+                    let mut tile_request = ~[]; //FIXME: try not to allocate if possible
+                    
+                    let mut y = world_offset.y as uint;
+                    while y < world_offset.y as uint + window_size.height + tile_size {
+                        let mut x = world_offset.x as uint;
+                        while x < world_offset.x as uint + window_size.width + tile_size {
+                            match *(quad.get_tile(x, y, *world_zoom)) {
+                                Some(ref current_tile) => {
+                                    if current_tile.resolution == *world_zoom {
+                                        x += tile_size;
+                                        loop; // we already have this tile
+                                    }
+                                }
+                                None => {} // fall through
+                            }
+                            let (tile_pos, new_tile_size) = quad.get_tile_rect(x, y, *world_zoom);
+                            tile_size = new_tile_size;
+                            x = tile_pos.x;
+                            y = tile_pos.y;
+                            
+                            // TODO: clamp tiles to page bounds
+                            // TODO: add null buffer/checkerboard tile to stop a flood of requests
+                            println(fmt!("requesting tile: (%?, %?): %?", x, y, tile_size));
+                            tile_request.push(Rect(Point2D(x, y), Size2D(tile_size, tile_size)));
+                            
+                            x += tile_size;
+                        }
+                        y += tile_size;
+                    }
+                    if !tile_request.is_empty() {
+                        match *render_chan {
+                            Some(ref chan) => {
+                                chan.send(ReRenderMsg(tile_request, *world_zoom));
+                            }
+                            _ => {}
+                        }
+                    }
+                }
+                _ => {}
+            }
+        };
+
         let update_layout_callbacks: @fn(LayoutChan) = |layout_chan: LayoutChan| {
             let layout_chan_clone = layout_chan.clone();
             do window.set_navigation_callback |direction| {
@@ -247,18 +325,32 @@ impl CompositorTask {
                     }
                     WindowMouseDownEvent(button, layer_mouse_point) => {
                         event = MouseDownEvent(button, world_mouse_point(layer_mouse_point));
-                    }
-                    WindowMouseUpEvent(button, layer_mouse_point) => {
                         
-                        // rerender layer at new zoom level
-                        // FIXME: this should happen when the user stops zooming, definitely not here
-                        match *render_chan {
-                            Some(ref r_chan) => {
-                                r_chan.send(ReRenderMsg(*world_zoom));
+                        //eschweic
+                        match *quadtree {
+                            Some(ref quad) => {
+
+/*                                let wmp = world_mouse_point(layer_mouse_point);
+                                println(fmt!("mouse: (%?, %?):", wmp.x as uint, wmp.y as uint)); 
+                                let buffer = quad.get_tile(wmp.x as uint, wmp.y as uint, *world_zoom);
+                                match *buffer {
+                                    None => println("None"),
+                                    Some(ref buffer) => println(fmt!("Some: (%?, %?), %?, %?", buffer.screen_pos.origin.x, buffer.screen_pos.origin.y, buffer.screen_pos.size.width, buffer.resolution)),
+                               
+                                } */
+
+                                println(quad.get_html());
                             }
-                            None => {} // Nothing to do
+                            None => {}
                         }
+                    }
+                    WindowMouseUpEvent(button, layer_mouse_point) => {
+                        
+                        //FIXME: this should not be here eschweic
+                        ask_for_tiles();
+
                         
+
                         event = MouseUpEvent(button, world_mouse_point(layer_mouse_point));
                     }
                 }
@@ -266,6 +358,7 @@ impl CompositorTask {
             }
         };
 
+
         let check_for_messages: @fn(&Port<Msg>) = |port: &Port<Msg>| {
             // Handle messages
             while port.peek() {
@@ -291,6 +384,21 @@ impl CompositorTask {
                     }
 
                     GetGLContext(chan) => chan.send(current_gl_context()),
+                    
+                    //eschweic
+                    NewLayer(new_size, tile_size) => {
+                        *page_size = Size2D(new_size.width as f32, new_size.height as f32);
+                        *quadtree = Some(Quadtree::new(0, 0, new_size.width, new_size.height, tile_size));
+                        ask_for_tiles();
+                        
+                    }
+                    ResizeLayer(new_size) => {
+                        *page_size = Size2D(new_size.width as f32, new_size.height as f32);
+                        // TODO: update quadtree, ask for tiles
+                    }
+                    DeleteLayer => {
+                        // TODO: create secondary layer tree, keep displaying until new tiles come in
+                    }
 
                     Paint(id, new_layer_buffer_set, new_size) => {
                         match *pipeline_id {
@@ -300,6 +408,12 @@ impl CompositorTask {
                             
                         debug!("osmain: received new frame");
 
+                        let quad;
+                        match *quadtree {
+                            Some(ref mut q) => quad = q,
+                            None => fail!("Compositor: given paint command with no quadtree initialized"),
+                        }
+
                         *page_size = Size2D(new_size.width as f32, new_size.height as f32);
 
                         let new_layer_buffer_set = new_layer_buffer_set.get();
@@ -307,12 +421,20 @@ impl CompositorTask {
                         // Iterate over the children of the container layer.
                         let mut current_layer_child = root_layer.first_child;
 
-                        for new_layer_buffer_set.buffers.iter().advance |buffer| {
+                        // Replace the image layer data with the buffer data.
+                        let buffers = util::replace(&mut new_layer_buffer_set.buffers, ~[]);
+
+                        do vec::consume(buffers) |_, buffer| {
+                            quad.add_tile(buffer.screen_pos.origin.x, buffer.screen_pos.origin.y,
+                                          *world_zoom, buffer);
+                        }
+                        
+                        for quad.get_all_tiles().each |buffer| {
                             let width = buffer.rect.size.width as uint;
                             let height = buffer.rect.size.height as uint;
 
                             debug!("osmain: compositing buffer rect %?", &buffer.rect);
-
+                            
                             // Find or create a texture layer.
                             let texture_layer;
                             current_layer_child = match current_layer_child {
@@ -339,9 +461,10 @@ impl CompositorTask {
                             let origin = Point2D(origin.x as f32, origin.y as f32);
 
                             // Set the layer's transform.
-                            let transform = identity().translate(origin.x, origin.y, 0.0);
-                            let transform = transform.scale(width as f32, height as f32, 1.0);
+                            let transform = identity().translate(origin.x * *world_zoom / buffer.resolution, origin.y * *world_zoom / buffer.resolution, 0.0);
+                            let transform = transform.scale(width as f32 * *world_zoom / buffer.resolution, height as f32 * *world_zoom / buffer.resolution, 1.0);
                             texture_layer.common.set_transform(transform);
+                            
                         }
 
                         // Delete leftover layers
@@ -409,6 +532,8 @@ impl CompositorTask {
             
             root_layer.common.set_transform(scroll_transform);
             
+//            ask_for_tiles();
+
             *recomposite = true;
         }
 
@@ -447,6 +572,7 @@ impl CompositorTask {
                                                       window_size.height as f32 / -2f32,
                                                       0.0);
             root_layer.common.set_transform(zoom_transform);
+//            ask_for_tiles();
             
             *recomposite = true;
         }
diff --git a/src/components/main/compositing/quadtree.rs b/src/components/main/compositing/quadtree.rs
index 8c3e426e5b6..e9fc4e65d85 100644
--- a/src/components/main/compositing/quadtree.rs
+++ b/src/components/main/compositing/quadtree.rs
@@ -52,7 +52,11 @@ impl<T> Quadtree<T> {
             max_tile_size: tile_size,
         }
     }
-    
+
+    /// Return the maximum allowed tile size
+    pub fn get_tile_size(&self) -> uint {
+        self.max_tile_size
+    }
     /// Get a tile at a given pixel position and scale.
     pub fn get_tile<'r>(&'r self, x: uint, y: uint, scale: f32) -> &'r Option<T> {
         self.root.get_tile(x as f32 / scale, y as f32 / scale)
@@ -61,12 +65,24 @@ impl<T> Quadtree<T> {
     pub fn add_tile(&mut self, x: uint, y: uint, scale: f32, tile: T) {
         self.root.add_tile(x as f32 / scale, y as f32 / scale, tile, self.max_tile_size as f32 / scale);
     }
-
+    /// Get the tile size/offset for a given pixel position
+    pub fn get_tile_rect(&self, x: uint, y: uint, scale: f32) -> (Point2D<uint>, uint) {
+        self.root.get_tile_rect(x as f32 / scale, y as f32 / scale, scale, self.max_tile_size as f32 / scale)
+    }
+    /// Get all the tiles in the tree
+    pub fn get_all_tiles<'r>(&'r self) -> ~[&'r T] {
+        self.root.get_all_tiles()
+    }
+    /// Generate html to visualize the tree
+    pub fn get_html(&self) -> ~str {
+        let header = "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\"> <html xmlns=\"http://www.w3.org/1999/xhtml\">";
+        fmt!("%s<body>%s</body></html>", header, self.root.get_html())
+    }
 
 }
 
 impl<T> QuadtreeNode<T> {
-    // Private method to create new children
+    /// Private method to create new children
     fn new_child(x: f32, y: f32, size: f32) -> QuadtreeNode<T> {
         QuadtreeNode {
             tile: None,
@@ -105,6 +121,26 @@ impl<T> QuadtreeNode<T> {
         }
     }
 
+    /// Get all tiles in the tree, parents first.
+    /// FIXME: this could probably be more efficient
+    fn get_all_tiles<'r>(&'r self) -> ~[&'r T] {
+        let mut ret = ~[];
+        
+        match self.tile {
+            Some (ref tile) => ret = ~[tile],
+            None => {}
+        }
+
+        for self.quadrants.each |quad| {
+            match *quad {
+                Some(ref child) => ret = ret + child.get_all_tiles(),
+                None => {}
+            }
+        }
+
+        return ret;
+    }
+
     /// Add a tile associated with a given position in page coords. If the tile size exceeds the maximum,
     /// the node will be split and the method will recurse until the tile size is within limits.
     fn add_tile(&mut self, x: f32, y: f32, tile: T, tile_size: f32) {
@@ -115,16 +151,16 @@ impl<T> QuadtreeNode<T> {
             fail!("Quadtree: Tried to add tile to invalid region");
         }
         
-        if self.size <= tile_size { // We are the child
+         if self.size <= tile_size { // We are the child
             self.tile = Some(tile);
-            for vec::each([TL, TR, BL, BR]) |quad| {
+            for [TL, TR, BL, BR].each |quad| {
                 self.quadrants[*quad as int] = None;
             }
-        } else { //send tile to children            
+        } else { // Send tile to children            
             let quad = self.get_quadrant(x, y);
             match self.quadrants[quad as int] {
                 Some(ref mut child) => child.add_tile(x, y, tile, tile_size),
-                None => { //make new child      
+                None => { // Make new child      
                     let new_size = self.size / 2.0;
                     let new_x = match quad {
                         TL | BL => self.origin.x,
@@ -138,19 +174,93 @@ impl<T> QuadtreeNode<T> {
                     c.add_tile(x, y, tile, tile_size);
                     self.quadrants[quad as int] = Some(c);
 
-                    // If we have 4 children, we probably shouldn't be hanging onto a tile
-                    // Though this isn't always true if we have grandchildren
+                    // If my tile is completely occluded, get rid of it.
+                    // FIXME: figure out a better way to determine if a tile is completely occluded
+                    // e.g. this alg doesn't work if a tile is covered by its grandchildren
                     match self.quadrants {
-                        [Some(_), Some(_), Some(_), Some(_)] => {
-                            self.tile = None;
+                        [Some(ref tl_child), Some(ref tr_child), Some(ref bl_child), Some(ref br_child)] => {
+                            match (&tl_child.tile, &tr_child.tile, &bl_child.tile, &br_child.tile) {
+                                (&Some(_), &Some(_), &Some(_), &Some(_)) => self.tile = None,
+                                _ => {}
+                            }
                         }
                         _ => {}
                     }
+                }
+            }
+        }
+    }
+
+    /// Get an origin and a width/height for a future tile for a given position in page coords
+    fn get_tile_rect(&self, x: f32, y: f32, scale: f32, tile_size: f32) -> (Point2D<uint>, uint) {    
+        if x >= self.origin.x + self.size || x < self.origin.x
+            || y >= self.origin.y + self.size || y < self.origin.y {
+            fail!("Quadtree: Tried to query a tile rect outside of range");
+        }
+        
+        if self.size <= tile_size {
+            let self_x = (self.origin.x * scale).ceil() as uint;
+            let self_y = (self.origin.y * scale).ceil() as uint;
+            let self_size = (self.size * scale).ceil() as uint;
+            return (Point2D(self_x, self_y), self_size);
+        }
+        
+        let index = self.get_quadrant(x,y) as int;
+        match self.quadrants[index] {
+            None => {
+                // calculate where the new tile should go
+                let factor = self.size / tile_size;
+                let divisor = uint::next_power_of_two(factor.ceil() as uint);
+                let new_size_page = self.size / (divisor as f32);
+                let new_size_pixel = (new_size_page * scale).ceil() as uint;
+
+                let new_x_page = self.origin.x + new_size_page * ((x - self.origin.x) / new_size_page).floor();
+                let new_y_page = self.origin.y + new_size_page * ((y - self.origin.y) / new_size_page).floor();
+                let new_x_pixel = (new_x_page * scale).ceil() as uint;
+                let new_y_pixel = (new_y_page * scale).ceil() as uint;
+                
+                (Point2D(new_x_pixel, new_y_pixel), new_size_pixel)
+            }
+            Some(ref child) => child.get_tile_rect(x, y, scale, tile_size),
+        }
+    }
 
+    /// Generate html to visualize the tree.
+    /// This is really inefficient, but it's for testing only.
+    fn get_html(&self) -> ~str {
+        let mut ret = ~"";
+        match self.tile {
+            Some(ref tile) => {
+                ret = fmt!("%s%?", ret, tile);
+            }
+            None => {
+                ret = fmt!("%sNO TILE", ret);
+            }
+        }
+        match self.quadrants {
+            [None, None, None, None] => {}
+            _ => {
+                ret = fmt!("%s<table border=1><tr>", ret);
+                for [TL, TR, BL, BR].each |quad| {
+                    match self.quadrants[*quad as int] {
+                        Some(ref child) => {
+                            ret = fmt!("%s<td>%s</td>", ret, child.get_html());
+                        }
+                        None => {
+                            ret = fmt!("%s<td>EMPTY CHILD</td>", ret);
+                        }
+                    }
+                    match *quad {
+                        TR => ret = fmt!("%s</tr><tr>", ret),
+                        _ => {}
+                    }
                 }
+                ret = fmt!("%s</table>\n", ret);
             }
         }
+        return ret;
     }
+
 }
 
 #[test]
diff --git a/src/components/msg/compositor_msg.rs b/src/components/msg/compositor_msg.rs
index d9dd02f2671..0763833357c 100644
--- a/src/components/msg/compositor_msg.rs
+++ b/src/components/msg/compositor_msg.rs
@@ -19,8 +19,12 @@ pub struct LayerBuffer {
     // The rect in pixels that will be drawn to the screen.
     screen_pos: Rect<uint>,
 
+    // The scale at which this tile is rendered
+    resolution: f32, //eschweic
+
     // NB: stride is in pixels, like OpenGL GL_UNPACK_ROW_LENGTH.
-    stride: uint
+    stride: uint,
+        
 }
 
 /// A set of layer buffers. This is an atomic unit used to switch between the front and back
@@ -49,6 +53,9 @@ pub enum ReadyState {
 /// submit them to be drawn to the display.
 pub trait RenderListener {
     fn get_gl_context(&self) -> AzGLContext;
+    fn new_layer(&self, Size2D<uint>, uint); //eschweic
+    fn resize_layer(&self, Size2D<uint>);
+    fn delete_layer(&self);
     fn paint(&self, id: uint, layer_buffer_set: arc::ARC<LayerBufferSet>, new_size: Size2D<uint>);
     fn set_render_state(&self, render_state: RenderState);
 }