Explicitly optional ClipID for stacking contexts

Author: kvark

examples/alpha_perf.rs

@@ -35,7 +35,8 @@ impl Example for App {
 
         builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],

examples/animation.rs

@@ -63,20 +63,20 @@ impl App {
             None,
         );
 
-        let space_and_clip = SpaceAndClipInfo {
-            spatial_id,
-            clip_id: ClipId::root(pipeline_id),
-        };
-
         builder.push_stacking_context(
             &LayoutPrimitiveInfo::new(LayoutRect::zero()),
-            &space_and_clip,
+            spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &filters,
             RasterSpace::Screen,
         );
 
+        let space_and_clip = SpaceAndClipInfo {
+            spatial_id,
+            clip_id: ClipId::root(pipeline_id),
+        };
         let clip_bounds = LayoutRect::new(LayoutPoint::zero(), bounds.size);
         let complex_clip = ComplexClipRegion {
             rect: clip_bounds,

examples/basic.rs

@@ -196,7 +196,8 @@ impl Example for App {
 
         builder.push_stacking_context(
             &info,
-            &root_space_and_clip,
+            spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],

examples/blob.rs

@@ -224,7 +224,8 @@ impl Example for App {
 
         builder.push_stacking_context(
             &api::LayoutPrimitiveInfo::new(bounds),
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             api::TransformStyle::Flat,
             api::MixBlendMode::Normal,
             &[],

examples/document.rs

@@ -114,7 +114,8 @@ impl Example for App {
 
             builder.push_stacking_context(
                 &LayoutPrimitiveInfo::new(doc.content_rect),
-                &space_and_clip,
+                space_and_clip.spatial_id,
+                None,
                 TransformStyle::Flat,
                 MixBlendMode::Normal,
                 &[],

examples/frame_output.rs

@@ -115,7 +115,8 @@ impl App {
 
         builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],
@@ -160,7 +161,8 @@ impl Example for App {
 
         builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],

examples/iframe.rs

@@ -40,7 +40,8 @@ impl Example for App {
         let info = LayoutPrimitiveInfo::new(sub_bounds);
         sub_builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],
@@ -73,7 +74,8 @@ impl Example for App {
         let info = LayoutPrimitiveInfo::new(sub_bounds);
         builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],

examples/image_resize.rs

@@ -43,7 +43,8 @@ impl Example for App {
 
         builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],

examples/multiwindow.rs

@@ -193,7 +193,8 @@ impl Window {
         let info = LayoutPrimitiveInfo::new(bounds);
         builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],

examples/scrolling.rs

@@ -36,7 +36,8 @@ impl Example for App {
         let root_space_and_clip = SpaceAndClipInfo::root_scroll(pipeline_id);
         builder.push_stacking_context(
             &info,
-            &root_space_and_clip,
+            root_space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],
@@ -49,7 +50,8 @@ impl Example for App {
             let scrollbox = (0, 0).to(300, 400);
             builder.push_stacking_context(
                 &LayoutPrimitiveInfo::new((10, 10).by(0, 0)),
-                &root_space_and_clip,
+                root_space_and_clip.spatial_id,
+                None,
                 TransformStyle::Flat,
                 MixBlendMode::Normal,
                 &[],

examples/texture_cache_stress.rs

@@ -100,7 +100,8 @@ impl Example for App {
 
         builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],

examples/yuv.rs

@@ -97,7 +97,8 @@ impl Example for App {
 
         builder.push_stacking_context(
             &info,
-            &space_and_clip,
+            space_and_clip.spatial_id,
+            None,
             TransformStyle::Flat,
             MixBlendMode::Normal,
             &[],

webrender/src/display_list_flattener.rs

@@ -432,7 +432,8 @@ impl<'a> DisplayListFlattener<'a> {
             TransformStyle::Flat,
             true,
             true,
-            &ScrollNodeAndClipChain::new(ROOT_SPATIAL_NODE_INDEX, ClipChainId::NONE),
+            ROOT_SPATIAL_NODE_INDEX,
+            ClipChainId::NONE,
             RasterSpace::Screen,
         );
 
@@ -589,9 +590,9 @@ impl<'a> DisplayListFlattener<'a> {
         traversal: &mut BuiltDisplayListIter<'a>,
         pipeline_id: PipelineId,
         stacking_context: &StackingContext,
+        spatial_node_index: SpatialNodeIndex,
         origin: LayoutPoint,
         filters: ItemRange<FilterOp>,
-        clip_and_scroll: &ScrollNodeAndClipChain,
         reference_frame_relative_offset: &LayoutVector2D,
         is_backface_visible: bool,
     ) {
@@ -610,13 +611,19 @@ impl<'a> DisplayListFlattener<'a> {
             )
         };
 
+        let clip_chain_id = match stacking_context.clip_id {
+            Some(clip_id) => self.id_to_index_mapper.get_clip_chain_id(clip_id),
+            None => ClipChainId::NONE,
+        };
+
         self.push_stacking_context(
             pipeline_id,
             composition_operations,
             stacking_context.transform_style,
             is_backface_visible,
             false,
-            clip_and_scroll,
+            spatial_node_index,
+            clip_chain_id,
             stacking_context.raster_space,
         );
 
@@ -831,24 +838,14 @@ impl<'a> DisplayListFlattener<'a> {
                 );
             }
             SpecificDisplayItem::PushStackingContext(ref info) => {
-                // Special handling of clip ids here: for Stacking Context it means
-                // forcing the intermediate surface and applying the clips on top.
-                // We only do this if the `ClipId` is non-root, otherwise we assume
-                // all the items to inherit the clips anyway.
-                let mut clip_and_scroll = clip_and_scroll;
-                if space_and_clip.clip_id.is_root() {
-                    debug_assert_eq!(space_and_clip.clip_id, ClipId::root(pipeline_id));
-                    clip_and_scroll.clip_chain_id = ClipChainId::NONE;
-                }
-
                 let mut subtraversal = item.sub_iter();
                 self.flatten_stacking_context(
                     &mut subtraversal,
                     pipeline_id,
                     &info.stacking_context,
+                    clip_and_scroll.spatial_node_index,
                     item.rect().origin,
                     item.filters(),
-                    &clip_and_scroll,
                     &reference_frame_relative_offset,
                     prim_info.is_backface_visible,
                 );
@@ -1210,7 +1207,8 @@ impl<'a> DisplayListFlattener<'a> {
         transform_style: TransformStyle,
         is_backface_visible: bool,
         is_pipeline_root: bool,
-        clip_and_scroll: &ScrollNodeAndClipChain,
+        spatial_node_index: SpatialNodeIndex,
+        clip_chain_id: ClipChainId,
         requested_raster_space: RasterSpace,
     ) {
         // Check if this stacking context is the root of a pipeline, and the caller
@@ -1279,7 +1277,7 @@ impl<'a> DisplayListFlattener<'a> {
         // has a clip node. In the future, we may decide during
         // prepare step to skip the intermediate surface if the
         // clip node doesn't affect the stacking context rect.
-        let should_isolate = clip_and_scroll.clip_chain_id != ClipChainId::NONE;
+        let should_isolate = clip_chain_id != ClipChainId::NONE;
 
         // Push the SC onto the stack, so we know how to handle things in
         // pop_stacking_context.
@@ -1288,8 +1286,8 @@ impl<'a> DisplayListFlattener<'a> {
             pipeline_id,
             is_backface_visible,
             requested_raster_space,
-            spatial_node_index: clip_and_scroll.spatial_node_index,
-            clip_chain_id: clip_and_scroll.clip_chain_id,
+            spatial_node_index,
+            clip_chain_id,
             frame_output_pipeline_id,
             composite_ops,
             should_isolate,

webrender_api/src/display_item.rs

@@ -541,6 +541,7 @@ pub struct PushStackingContextDisplayItem {
 pub struct StackingContext {
     pub transform_style: TransformStyle,
     pub mix_blend_mode: MixBlendMode,
+    pub clip_id: Option<ClipId>,
     pub raster_space: RasterSpace,
 } // IMPLICIT: filters: Vec<FilterOp>
 

webrender_api/src/display_list.rs

@@ -1298,7 +1298,8 @@ impl DisplayListBuilder {
     pub fn push_stacking_context(
         &mut self,
         layout: &LayoutPrimitiveInfo,
-        space_and_clip: &SpaceAndClipInfo,
+        spatial_id: SpatialId,
+        clip_id: Option<ClipId>,
         transform_style: TransformStyle,
         mix_blend_mode: MixBlendMode,
         filters: &[FilterOp],
@@ -1308,11 +1309,15 @@ impl DisplayListBuilder {
             stacking_context: StackingContext {
                 transform_style,
                 mix_blend_mode,
+                clip_id,
                 raster_space,
             },
         });
 
-        self.push_item(&item, layout, space_and_clip);
+        self.push_item(&item, layout, &SpaceAndClipInfo {
+            spatial_id,
+            clip_id: ClipId::invalid(),
+        });
         self.push_iter(filters);
     }
 

wrench/src/yaml_frame_reader.rs

@@ -1754,17 +1754,14 @@ impl YamlFrameReader {
         }
 
         let filters = yaml["filters"].as_vec_filter_op().unwrap_or(vec![]);
-        let root_clip_id = ClipId::root(dl.pipeline_id);
 
         info.rect = bounds;
         info.clip_rect = bounds;
 
         dl.push_stacking_context(
             &info,
-            &SpaceAndClipInfo {
-                spatial_id: *self.spatial_id_stack.last().unwrap(),
-                clip_id: clip_node_id.unwrap_or(root_clip_id),
-            },
+            *self.spatial_id_stack.last().unwrap(),
+            clip_node_id,
             transform_style,
             mix_blend_mode,
             &filters,