Bug 1715194 - Fix tiled clip image masks + raster roots. r=gfx-reviewers,lsalzman

Ensure that tiled image clip masks are calculated relative to the
raster root, not world space. Add a regression test for this.

Differential Revision: https://phabricator.services.mozilla.com/D117122

gfx/wr/webrender/src/batch.rs

@@ -3568,8 +3568,8 @@ impl ClipBatcher {
                         tile: None,
                     };
 
-                    let map_local_to_world = SpaceMapper::new_with_target(
-                        ROOT_SPATIAL_NODE_INDEX,
+                    let map_local_to_raster = SpaceMapper::new_with_target(
+                        root_spatial_node_index,
                         clip_instance.spatial_node_index,
                         WorldRect::max_rect().to_rect(),
                         spatial_tree,
@@ -3591,12 +3591,12 @@ impl ClipBatcher {
                         // to the shader and also set up a scissor rect for the overall target bounds to
                         // ensure nothing is drawn outside the target. If for some reason we can't map the
                         // rect back to local space, we also fall back to just using a scissor rectangle.
-                        let world_rect =
+                        let raster_rect =
                             sub_rect.translate(actual_rect.min.to_vector()) / surface_device_pixel_scale;
-                        let (clip_transform_id, local_rect, scissor) = match map_local_to_world.unmap(&world_rect.to_rect()) {
+                        let (clip_transform_id, local_rect, scissor) = match map_local_to_raster.unmap(&raster_rect.to_rect()) {
                             Some(local_rect)
                                 if clip_transform_id.transform_kind() == TransformedRectKind::AxisAligned &&
-                                   !map_local_to_world.get_transform().has_perspective_component() => {
+                                   !map_local_to_raster.get_transform().has_perspective_component() => {
                                     match local_rect.intersection(&rect) {
                                         Some(local_rect) => (clip_transform_id, local_rect, None),
                                         None => return,
@@ -3638,11 +3638,11 @@ impl ClipBatcher {
 
                         for tile in clip_store.visible_mask_tiles(&clip_instance) {
                             let tile_sub_rect = if clip_is_axis_aligned {
-                                let tile_world_rect = map_local_to_world
+                                let tile_raster_rect = map_local_to_raster
                                     .map(&tile.tile_rect)
                                     .expect("bug: should always map as axis-aligned")
                                     .to_box2d();
-                                let tile_device_rect = tile_world_rect * surface_device_pixel_scale;
+                                let tile_device_rect = tile_raster_rect * surface_device_pixel_scale;
                                 tile_device_rect
                                     .translate(-actual_rect.min.to_vector())
                                     .round_out()
@@ -3669,7 +3669,7 @@ impl ClipBatcher {
                     // the image boundaries will be properly initialized.
                     if is_first_clip &&
                         (!clip_is_axis_aligned ||
-                         !(map_local_to_world.map(&rect).expect("bug: should always map as axis-aligned")
+                         !(map_local_to_raster.map(&rect).expect("bug: should always map as axis-aligned")
                             * surface_device_pixel_scale).contains_rect(&actual_rect.to_rect())) {
                         clear_to_one = true;
                     }

gfx/wr/wrench/reftests/clip/raster-roots-tiled-mask-ref.yaml

@@ -0,0 +1,6 @@
+---
+root:
+  items:
+    - type: rect
+      bounds: [0, 0, 8, 128]
+      color: [255, 0, 0, 0.5]

gfx/wr/wrench/reftests/clip/raster-roots-tiled-mask.yaml

@@ -0,0 +1,20 @@
+# Verify that tiled image clip masks are correctly positioned when the
+# underlying surface has established a raster root
+---
+root:
+  items:
+    - type: scroll-frame
+      bounds: [0, 0, 8, 1024]
+      content-size: [8, 2048]
+      scroll-offset: [0, 1024]
+      items:
+        - type: clip
+          bounds: [0, 0, 8, 2048]
+          image-mask:
+            image: solid-color(128,0,0,0,8,1024)
+            rect: [0, 0, 8, 2048]
+            repeat: false
+          items:
+            - type: rect
+              bounds: [0, 1024, 8, 128]
+              color: red

gfx/wr/wrench/reftests/clip/reftest.list

@@ -19,3 +19,4 @@ color_targets(1) alpha_targets(0) == clip-out-rotation.yaml blank.yaml # Unexpec
 == clip-rectangle-redundant-sc.yaml clip-rectangle-redundant-sc-ref.yaml
 fuzzy(128,707) == clip-filter-raster-root.yaml clip-filter-raster-root-ref.yaml
 == blend-container.yaml blend-container-ref.yaml
+== raster-roots-tiled-mask.yaml raster-roots-tiled-mask-ref.yaml