Bug 1674029 - Adjust compositor surface tile dirty rects by their transform if applicable. r=gw

Differential Revision: https://phabricator.services.mozilla.com/D96494

gfx/wr/webrender/src/composite.rs

@@ -94,6 +94,7 @@ pub struct CompositeTile {
     pub clip_rect: DeviceRect,
     pub dirty_rect: DeviceRect,
     pub valid_rect: DeviceRect,
+    pub transform: Option<CompositorSurfaceTransform>,
     pub z_id: ZBufferId,
 }
 
@@ -569,6 +570,7 @@ impl CompositeState {
                 valid_rect: tile.device_valid_rect.translate(-device_rect.origin.to_vector()),
                 dirty_rect: tile.device_dirty_rect.translate(-device_rect.origin.to_vector()),
                 clip_rect: device_clip_rect,
+                transform: None,
                 z_id: tile.z_id,
             };
 
@@ -738,6 +740,7 @@ impl CompositeState {
                 valid_rect: external_surface.device_rect.translate(-external_surface.device_rect.origin.to_vector()),
                 dirty_rect: external_surface.device_rect.translate(-external_surface.device_rect.origin.to_vector()),
                 clip_rect,
+                transform: Some(external_surface.transform),
                 z_id: external_surface.z_id,
             };
 

gfx/wr/webrender/src/renderer.rs

@@ -6034,7 +6034,15 @@ impl Renderer {
                 // what the device supports.
                 for tile in composite_state.opaque_tiles.iter().chain(composite_state.alpha_tiles.iter()) {
                     let tile_dirty_rect = tile.dirty_rect.translate(tile.rect.origin.to_vector());
-                    combined_dirty_rect = combined_dirty_rect.union(&tile_dirty_rect);
+                    let transformed_dirty_rect = if let Some(transform) = tile.transform {
+                        transform.outer_transformed_rect(&tile_dirty_rect)
+                    } else {
+                        Some(tile_dirty_rect)
+                    };
+
+                    if let Some(dirty_rect) = transformed_dirty_rect {
+                        combined_dirty_rect = combined_dirty_rect.union(&dirty_rect);
+                    }
                 }
 
                 let combined_dirty_rect = combined_dirty_rect.round();