[Impeller] Disable compute for Vulkan. (flutter/engine#49463)

This code is missing correct barriers which cannot be specified at the HAL level, see https://github.com/flutter/flutter/issues/140798

engine/src/flutter/impeller/entity/entity_unittests.cc

@@ -40,6 +40,7 @@
 #include "impeller/geometry/color.h"
 #include "impeller/geometry/geometry_asserts.h"
 #include "impeller/geometry/path_builder.h"
+#include "impeller/geometry/point.h"
 #include "impeller/geometry/sigma.h"
 #include "impeller/geometry/vector.h"
 #include "impeller/playground/playground.h"
@@ -2426,6 +2427,11 @@ TEST_P(EntityTest, PointFieldGeometryCoverage) {
             Rect::MakeLTRB(35, 15, 135, 205));
 }
 
+TEST_P(EntityTest, PointFieldCanUseCompute) {
+  EXPECT_EQ(PointFieldGeometry::CanUseCompute(*GetContentContext()),
+            GetContext()->GetBackendType() == Context::BackendType::kMetal);
+}
+
 TEST_P(EntityTest, ColorFilterContentsWithLargeGeometry) {
   Entity entity;
   entity.SetTransform(Matrix::MakeScale(GetContentScale()));

engine/src/flutter/impeller/entity/geometry/point_field_geometry.cc

@@ -18,7 +18,7 @@ GeometryResult PointFieldGeometry::GetPositionBuffer(
     const ContentContext& renderer,
     const Entity& entity,
     RenderPass& pass) const {
-  if (renderer.GetDeviceCapabilities().SupportsCompute()) {
+  if (CanUseCompute(renderer)) {
     return GetPositionBufferGPU(renderer, entity, pass);
   }
   auto vtx_builder = GetPositionBufferCPU(renderer, entity, pass);
@@ -42,7 +42,7 @@ GeometryResult PointFieldGeometry::GetPositionUVBuffer(
     const ContentContext& renderer,
     const Entity& entity,
     RenderPass& pass) const {
-  if (renderer.GetDeviceCapabilities().SupportsCompute()) {
+  if (CanUseCompute(renderer)) {
     return GetPositionBufferGPU(renderer, entity, pass, texture_coverage,
                                 effect_transform);
   }
@@ -275,6 +275,14 @@ GeometryVertexType PointFieldGeometry::GetVertexType() const {
   return GeometryVertexType::kPosition;
 }
 
+// Compute is disabled for Vulkan because the barriers are incorrect, see
+// also: https://github.com/flutter/flutter/issues/140798 .
+bool PointFieldGeometry::CanUseCompute(const ContentContext& renderer) {
+  return renderer.GetDeviceCapabilities().SupportsCompute() &&
+         renderer.GetContext()->GetBackendType() ==
+             Context::BackendType::kMetal;
+}
+
 // |Geometry|
 std::optional<Rect> PointFieldGeometry::GetCoverage(
     const Matrix& transform) const {

engine/src/flutter/impeller/entity/geometry/point_field_geometry.h

@@ -17,6 +17,9 @@ class PointFieldGeometry final : public Geometry {
 
   static size_t ComputeCircleDivisions(Scalar scaled_radius, bool round);
 
+  /// If the platform can use compute safely.
+  static bool CanUseCompute(const ContentContext& renderer);
+
  private:
   // |Geometry|
   GeometryResult GetPositionBuffer(const ContentContext& renderer,