[Impeller] Fix the rendering issue when the tile mode of gradient is set to 'decal'

Author: ColdPaleLight

impeller/aiks/aiks_unittests.cc

@@ -791,6 +791,37 @@ TEST_P(AiksTest, CanRenderConicalGradient) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+TEST_P(AiksTest, CanRenderGradientDecalWithBackground) {
+  std::vector<Color> colors = {Color::MakeRGBA8(0xF4, 0x43, 0x36, 0xFF),
+                               Color::MakeRGBA8(0xFF, 0xEB, 0x3B, 0xFF),
+                               Color::MakeRGBA8(0x4c, 0xAF, 0x50, 0xFF),
+                               Color::MakeRGBA8(0x21, 0x96, 0xF3, 0xFF)};
+  std::vector<Scalar> stops = {0.0, 1.f / 3.f, 2.f / 3.f, 1.0};
+
+  std::array<ColorSource, 3> color_sources = {
+      ColorSource::MakeLinearGradient({0, 0}, {100, 100}, colors, stops,
+                                      Entity::TileMode::kDecal, {}),
+      ColorSource::MakeRadialGradient({100, 100}, 100, colors, stops,
+                                      Entity::TileMode::kDecal, {}),
+      ColorSource::MakeSweepGradient({100, 100}, Degrees(45), Degrees(135),
+                                     colors, stops, Entity::TileMode::kDecal,
+                                     {}),
+  };
+
+  Canvas canvas;
+  Paint paint;
+  paint.color = Color::White();
+  canvas.DrawRect(Rect::MakeLTRB(0, 0, 605, 205), paint);
+  for (int i = 0; i < 3; i++) {
+    canvas.Save();
+    canvas.Translate({i * 200.0f, 0, 0});
+    paint.color_source = color_sources[i];
+    canvas.DrawRect(Rect::MakeLTRB(0, 0, 200, 200), paint);
+    canvas.Restore();
+  }
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 TEST_P(AiksTest, CanRenderDifferentShapesWithSameColorSource) {
   Canvas canvas;
   Paint paint;

impeller/entity/contents/linear_gradient_contents.cc

@@ -45,7 +45,7 @@ void LinearGradientContents::SetTileMode(Entity::TileMode tile_mode) {
 }
 
 bool LinearGradientContents::IsOpaque() const {
-  if (GetOpacity() < 1) {
+  if (GetOpacity() < 1 || tile_mode_ == Entity::TileMode::kDecal) {
     return false;
   }
   for (auto color : colors_) {

impeller/entity/contents/radial_gradient_contents.cc

@@ -46,7 +46,7 @@ const std::vector<Scalar>& RadialGradientContents::GetStops() const {
 }
 
 bool RadialGradientContents::IsOpaque() const {
-  if (GetOpacity() < 1) {
+  if (GetOpacity() < 1 || tile_mode_ == Entity::TileMode::kDecal) {
     return false;
   }
   for (auto color : colors_) {

impeller/entity/contents/sweep_gradient_contents.cc

@@ -51,7 +51,7 @@ const std::vector<Scalar>& SweepGradientContents::GetStops() const {
 }
 
 bool SweepGradientContents::IsOpaque() const {
-  if (GetOpacity() < 1) {
+  if (GetOpacity() < 1 || tile_mode_ == Entity::TileMode::kDecal) {
     return false;
   }
   for (auto color : colors_) {

impeller/entity/contents/tiled_texture_contents.cc

@@ -103,7 +103,8 @@ bool TiledTextureContents::UsesEmulatedTileMode(
 
 // |Contents|
 bool TiledTextureContents::IsOpaque() const {
-  if (GetOpacity() < 1) {
+  if (GetOpacity() < 1 || x_tile_mode_ == Entity::TileMode::kDecal ||
+      y_tile_mode_ == Entity::TileMode::kDecal) {
     return false;
   }
   if (color_filter_.has_value()) {

impeller/entity/entity_unittests.cc

@@ -2556,6 +2556,9 @@ TEST_P(EntityTest, LinearGradientContentsIsOpaque) {
   ASSERT_TRUE(contents.IsOpaque());
   contents.SetColors({Color::CornflowerBlue().WithAlpha(0.5)});
   ASSERT_FALSE(contents.IsOpaque());
+  contents.SetColors({Color::CornflowerBlue()});
+  contents.SetTileMode(Entity::TileMode::kDecal);
+  ASSERT_FALSE(contents.IsOpaque());
 }
 
 TEST_P(EntityTest, RadialGradientContentsIsOpaque) {
@@ -2564,6 +2567,9 @@ TEST_P(EntityTest, RadialGradientContentsIsOpaque) {
   ASSERT_TRUE(contents.IsOpaque());
   contents.SetColors({Color::CornflowerBlue().WithAlpha(0.5)});
   ASSERT_FALSE(contents.IsOpaque());
+  contents.SetColors({Color::CornflowerBlue()});
+  contents.SetTileMode(Entity::TileMode::kDecal);
+  ASSERT_FALSE(contents.IsOpaque());
 }
 
 TEST_P(EntityTest, SweepGradientContentsIsOpaque) {
@@ -2572,6 +2578,9 @@ TEST_P(EntityTest, SweepGradientContentsIsOpaque) {
   ASSERT_TRUE(contents.IsOpaque());
   contents.SetColors({Color::CornflowerBlue().WithAlpha(0.5)});
   ASSERT_FALSE(contents.IsOpaque());
+  contents.SetColors({Color::CornflowerBlue()});
+  contents.SetTileMode(Entity::TileMode::kDecal);
+  ASSERT_FALSE(contents.IsOpaque());
 }
 
 TEST_P(EntityTest, TiledTextureContentsIsOpaque) {