[DisplayList] Pre-Compute saveLayer bounds in DLBuilder (#50935)

Previously the DisplayListBuilder would only pass along bounds for a saveLayer when they were supplied by the caller that was building the DisplayList. This would require Impeller to use post-processing of the EntityPass lists to compute them on its own.

DisplayList can now compute those bounds as it builds the DisplayList to save dispatch clients from having to do so on their own. It will also provide an indicator in the case when the caller supplied bounds that ended up being too small to capture all of the content, causing clipping by the layer render target.

Author: flar

display_list/benchmarking/dl_complexity_gl.cc

@@ -49,7 +49,7 @@ unsigned int DisplayListGLComplexityCalculator::GLHelper::BatchedComplexity() {
 }
 
 void DisplayListGLComplexityCalculator::GLHelper::saveLayer(
-    const SkRect* bounds,
+    const SkRect& bounds,
     const SaveLayerOptions options,
     const DlImageFilter* backdrop) {
   if (IsComplex()) {
@@ -615,7 +615,8 @@ void DisplayListGLComplexityCalculator::GLHelper::drawDisplayList(
   }
   GLHelper helper(Ceiling() - CurrentComplexityScore());
   if (opacity < SK_Scalar1 && !display_list->can_apply_group_opacity()) {
-    helper.saveLayer(nullptr, SaveLayerOptions::kWithAttributes, nullptr);
+    auto bounds = display_list->bounds();
+    helper.saveLayer(bounds, SaveLayerOptions::kWithAttributes, nullptr);
   }
   display_list->Dispatch(helper);
   AccumulateComplexity(helper.ComplexityScore());

display_list/benchmarking/dl_complexity_gl.h

@@ -35,7 +35,7 @@ class DisplayListGLComplexityCalculator
     explicit GLHelper(unsigned int ceiling)
         : ComplexityCalculatorHelper(ceiling) {}
 
-    void saveLayer(const SkRect* bounds,
+    void saveLayer(const SkRect& bounds,
                    const SaveLayerOptions options,
                    const DlImageFilter* backdrop) override;
 

display_list/benchmarking/dl_complexity_metal.cc

@@ -63,7 +63,7 @@ DisplayListMetalComplexityCalculator::MetalHelper::BatchedComplexity() {
 }
 
 void DisplayListMetalComplexityCalculator::MetalHelper::saveLayer(
-    const SkRect* bounds,
+    const SkRect& bounds,
     const SaveLayerOptions options,
     const DlImageFilter* backdrop) {
   if (IsComplex()) {
@@ -559,7 +559,8 @@ void DisplayListMetalComplexityCalculator::MetalHelper::drawDisplayList(
   }
   MetalHelper helper(Ceiling() - CurrentComplexityScore());
   if (opacity < SK_Scalar1 && !display_list->can_apply_group_opacity()) {
-    helper.saveLayer(nullptr, SaveLayerOptions::kWithAttributes, nullptr);
+    auto bounds = display_list->bounds();
+    helper.saveLayer(bounds, SaveLayerOptions::kWithAttributes, nullptr);
   }
   display_list->Dispatch(helper);
   AccumulateComplexity(helper.ComplexityScore());

display_list/benchmarking/dl_complexity_metal.h

@@ -35,7 +35,7 @@ class DisplayListMetalComplexityCalculator
     explicit MetalHelper(unsigned int ceiling)
         : ComplexityCalculatorHelper(ceiling) {}
 
-    void saveLayer(const SkRect* bounds,
+    void saveLayer(const SkRect& bounds,
                    const SaveLayerOptions options,
                    const DlImageFilter* backdrop) override;
 

display_list/display_list.h

@@ -88,9 +88,7 @@ namespace flutter {
                                     \
   V(Save)                           \
   V(SaveLayer)                      \
-  V(SaveLayerBounds)                \
   V(SaveLayerBackdrop)              \
-  V(SaveLayerBackdropBounds)        \
   V(Restore)                        \
                                     \
   V(Translate)                      \
@@ -165,6 +163,7 @@ class SaveLayerOptions {
   SaveLayerOptions without_optimizations() const {
     SaveLayerOptions options;
     options.fRendersWithAttributes = fRendersWithAttributes;
+    options.fBoundsFromCaller = fBoundsFromCaller;
     return options;
   }
 
@@ -182,6 +181,33 @@ class SaveLayerOptions {
     return options;
   }
 
+  // Returns true iff the bounds for the saveLayer operation were provided
+  // by the caller, otherwise the bounds will have been computed by the
+  // DisplayListBuilder and provided for reference.
+  bool bounds_from_caller() const { return fBoundsFromCaller; }
+  SaveLayerOptions with_bounds_from_caller() const {
+    SaveLayerOptions options(this);
+    options.fBoundsFromCaller = true;
+    return options;
+  }
+  SaveLayerOptions without_bounds_from_caller() const {
+    SaveLayerOptions options(this);
+    options.fBoundsFromCaller = false;
+    return options;
+  }
+  bool bounds_were_calculated() const { return !fBoundsFromCaller; }
+
+  // Returns true iff the bounds for the saveLayer do not fully cover the
+  // contained rendering operations. This will only occur if the original
+  // caller supplied bounds and those bounds were not a strict superset
+  // of the content bounds computed by the DisplayListBuilder.
+  bool content_is_clipped() const { return fContentIsClipped; }
+  SaveLayerOptions with_content_is_clipped() const {
+    SaveLayerOptions options(this);
+    options.fContentIsClipped = true;
+    return options;
+  }
+
   SaveLayerOptions& operator=(const SaveLayerOptions& other) {
     flags_ = other.flags_;
     return *this;
@@ -198,6 +224,8 @@ class SaveLayerOptions {
     struct {
       unsigned fRendersWithAttributes : 1;
       unsigned fCanDistributeOpacity : 1;
+      unsigned fBoundsFromCaller : 1;
+      unsigned fContentIsClipped : 1;
     };
     uint32_t flags_;
   };