[Impeller] Turn off Aiks bounds tracking for filtered SaveLayers. (#49076)

We use this bounds rect for querying the DisplayList rtree when culling.
But when sub-DisplayLists are being dispatched, the DisplayList's rtree
is local and doesn't incorporate parent layer filters. So
sub-DisplayLists are getting culled as if no filters are being applied.

Technically our local bounds tracking in Aiks is actually correct here,
but this is a quick fix to alleviate the problem. I don't know what the
best longterm solution for this is.

Author: bdero

impeller/aiks/canvas.cc

@@ -681,6 +681,14 @@ void Canvas::SaveLayer(const Paint& paint,
   TRACE_EVENT0("flutter", "Canvas::saveLayer");
   Save(true, paint.blend_mode, backdrop_filter);
 
+  // The DisplayList bounds/rtree doesn't account for filters applied to parent
+  // layers, and so sub-DisplayLists are getting culled as if no filters are
+  // applied.
+  // See also: https://github.com/flutter/flutter/issues/139294
+  if (paint.image_filter) {
+    transform_stack_.back().cull_rect = std::nullopt;
+  }
+
   auto& new_layer_pass = GetCurrentPass();
   new_layer_pass.SetBoundsLimit(bounds);
 

impeller/aiks/canvas_unittests.cc

@@ -4,6 +4,7 @@
 
 #include "flutter/testing/testing.h"
 #include "impeller/aiks/canvas.h"
+#include "impeller/aiks/image_filter.h"
 #include "impeller/geometry/path_builder.h"
 
 // TODO(zanderso): https://github.com/flutter/flutter/issues/127701
@@ -336,6 +337,23 @@ TEST(AiksCanvasTest, PathClipDiffAgainstFullyCoveredCullRect) {
   ASSERT_EQ(canvas.GetCurrentLocalCullingBounds().value(), result_cull);
 }
 
+TEST(AiksCanvasTest, DisableLocalBoundsRectForFilteredSaveLayers) {
+  Rect initial_cull = Rect::MakeXYWH(0, 0, 10, 10);
+
+  Canvas canvas(initial_cull);
+  ASSERT_TRUE(canvas.GetCurrentLocalCullingBounds().has_value());
+
+  canvas.Save();
+  canvas.SaveLayer(
+      Paint{.image_filter = ImageFilter::MakeBlur(
+                Sigma(10), Sigma(10), FilterContents::BlurStyle::kNormal,
+                Entity::TileMode::kDecal)});
+  ASSERT_FALSE(canvas.GetCurrentLocalCullingBounds().has_value());
+
+  canvas.Restore();
+  ASSERT_TRUE(canvas.GetCurrentLocalCullingBounds().has_value());
+}
+
 }  // namespace testing
 }  // namespace impeller