[Impeller] Add backdrop filter support; refactor EntityPass (flutter#33887)

Author: bdero

ci/licenses_golden/licenses_flutter

@@ -568,6 +568,8 @@ FILE: ../../../flutter/impeller/entity/entity_pass_delegate.h
 FILE: ../../../flutter/impeller/entity/entity_playground.cc
 FILE: ../../../flutter/impeller/entity/entity_playground.h
 FILE: ../../../flutter/impeller/entity/entity_unittests.cc
+FILE: ../../../flutter/impeller/entity/inline_pass_context.cc
+FILE: ../../../flutter/impeller/entity/inline_pass_context.h
 FILE: ../../../flutter/impeller/entity/shaders/blending/advanced_blend.glsl
 FILE: ../../../flutter/impeller/entity/shaders/blending/advanced_blend.vert
 FILE: ../../../flutter/impeller/entity/shaders/blending/advanced_blend_color.frag

impeller/aiks/canvas.cc

@@ -265,14 +265,17 @@ size_t Canvas::GetStencilDepth() const {
   return xformation_stack_.back().stencil_depth;
 }
 
-void Canvas::SaveLayer(Paint paint, std::optional<Rect> bounds) {
+void Canvas::SaveLayer(Paint paint,
+                       std::optional<Rect> bounds,
+                       std::optional<Paint::ImageFilterProc> backdrop_filter) {
   Save(true, paint.blend_mode);
 
   auto& new_layer_pass = GetCurrentPass();
   new_layer_pass.SetDelegate(
       std::make_unique<PaintPassDelegate>(paint, bounds));
+  new_layer_pass.SetBackdropFilter(backdrop_filter);
 
-  if (bounds.has_value()) {
+  if (bounds.has_value() && !backdrop_filter.has_value()) {
     // Render target switches due to a save layer can be elided. In such cases
     // where passes are collapsed into their parent, the clipping effect to
     // the size of the render target that would have been allocated will be

impeller/aiks/canvas.h

@@ -35,7 +35,10 @@ class Canvas {
 
   void Save();
 
-  void SaveLayer(Paint paint, std::optional<Rect> bounds = std::nullopt);
+  void SaveLayer(
+      Paint paint,
+      std::optional<Rect> bounds = std::nullopt,
+      std::optional<Paint::ImageFilterProc> backdrop_filter = std::nullopt);
 
   bool Restore();
 

impeller/display_list/display_list_dispatcher.cc

@@ -324,9 +324,12 @@ void DisplayListDispatcher::setMaskFilter(const flutter::DlMaskFilter* filter) {
   }
 }
 
-// |flutter::Dispatcher|
-void DisplayListDispatcher::setImageFilter(
+static std::optional<Paint::ImageFilterProc> ToImageFilterProc(
     const flutter::DlImageFilter* filter) {
+  if (filter == nullptr) {
+    return std::nullopt;
+  }
+
   switch (filter->type()) {
     case flutter::DlImageFilterType::kBlur: {
       auto blur = filter->asBlur();
@@ -338,7 +341,7 @@ void DisplayListDispatcher::setImageFilter(
         UNIMPLEMENTED;
       }
 
-      paint_.image_filter = [sigma_x, sigma_y](FilterInput::Ref input) {
+      return [sigma_x, sigma_y](FilterInput::Ref input) {
         return FilterContents::MakeGaussianBlur(input, sigma_x, sigma_y);
       };
 
@@ -350,11 +353,16 @@ void DisplayListDispatcher::setImageFilter(
     case flutter::DlImageFilterType::kComposeFilter:
     case flutter::DlImageFilterType::kColorFilter:
     case flutter::DlImageFilterType::kUnknown:
-      UNIMPLEMENTED;
-      break;
+      return std::nullopt;
   }
 }
 
+// |flutter::Dispatcher|
+void DisplayListDispatcher::setImageFilter(
+    const flutter::DlImageFilter* filter) {
+  paint_.image_filter = ToImageFilterProc(filter);
+}
+
 // |flutter::Dispatcher|
 void DisplayListDispatcher::save() {
   canvas_.Save();
@@ -371,11 +379,8 @@ static std::optional<Rect> ToRect(const SkRect* rect) {
 void DisplayListDispatcher::saveLayer(const SkRect* bounds,
                                       const flutter::SaveLayerOptions options,
                                       const flutter::DlImageFilter* backdrop) {
-  if (backdrop) {
-    UNIMPLEMENTED;
-  }
-  canvas_.SaveLayer(options.renders_with_attributes() ? paint_ : Paint{},
-                    ToRect(bounds));
+  auto paint = options.renders_with_attributes() ? paint_ : Paint{};
+  canvas_.SaveLayer(paint, ToRect(bounds), ToImageFilterProc(backdrop));
 }
 
 // |flutter::Dispatcher|

impeller/display_list/display_list_unittests.cc

@@ -3,8 +3,10 @@
 // found in the LICENSE file.
 
 #include "display_list/display_list_blend_mode.h"
+#include "display_list/display_list_color.h"
 #include "display_list/display_list_color_filter.h"
 #include "display_list/display_list_image_filter.h"
+#include "display_list/display_list_paint.h"
 #include "display_list/display_list_tile_mode.h"
 #include "gtest/gtest.h"
 #include "third_party/imgui/imgui.h"
@@ -285,5 +287,64 @@ TEST_P(DisplayListTest, CanDrawWithImageBlurFilter) {
   ASSERT_TRUE(OpenPlaygroundHere(callback));
 }
 
+TEST_P(DisplayListTest, CanDrawBackdropFilter) {
+  auto texture = CreateTextureForFixture("embarcadero.jpg");
+
+  bool first_frame = true;
+  auto callback = [&]() {
+    if (first_frame) {
+      first_frame = false;
+      ImGui::SetNextWindowSize({400, 100});
+      ImGui::SetNextWindowPos({300, 650});
+    }
+
+    static float sigma[] = {10, 10};
+    static bool use_bounds = true;
+    static bool draw_circle = true;
+
+    ImGui::Begin("Controls");
+    ImGui::SliderFloat2("Sigma", sigma, 0, 100);
+    ImGui::Checkbox("Use SaveLayer bounds", &use_bounds);
+    ImGui::Checkbox("Draw child element", &draw_circle);
+    ImGui::End();
+
+    flutter::DisplayListBuilder builder;
+
+    Vector2 scale = GetContentScale();
+    builder.scale(scale.x, scale.y);
+
+    auto filter = flutter::DlBlurImageFilter(sigma[0], sigma[1],
+                                             flutter::DlTileMode::kClamp);
+
+    std::optional<SkRect> bounds;
+    if (use_bounds) {
+      auto [p1, p2] = IMPELLER_PLAYGROUND_LINE(
+          Point(250, 150), Point(800, 600), 20, Color::White(), Color::White());
+      bounds = SkRect::MakeLTRB(p1.x, p1.y, p2.x, p2.y);
+    }
+
+    builder.drawImage(DlImageImpeller::Make(texture), SkPoint::Make(200, 200),
+                      SkSamplingOptions{}, true);
+    builder.saveLayer(bounds.has_value() ? &bounds.value() : nullptr, nullptr,
+                      &filter);
+
+    if (draw_circle) {
+      auto circle_center =
+          IMPELLER_PLAYGROUND_POINT(Point(500, 400), 20, Color::Red());
+
+      builder.setStyle(flutter::DlDrawStyle::kStroke);
+      builder.setStrokeCap(flutter::DlStrokeCap::kButt);
+      builder.setStrokeJoin(flutter::DlStrokeJoin::kBevel);
+      builder.setStrokeWidth(10);
+      builder.setColor(flutter::DlColor::kRed().withAlpha(100));
+      builder.drawCircle({circle_center.x, circle_center.y}, 100);
+    }
+
+    return builder.Build();
+  };
+
+  ASSERT_TRUE(OpenPlaygroundHere(callback));
+}
+
 }  // namespace testing
 }  // namespace impeller

impeller/entity/BUILD.gn

@@ -87,6 +87,8 @@ impeller_component("entity") {
     "entity_pass.h",
     "entity_pass_delegate.cc",
     "entity_pass_delegate.h",
+    "inline_pass_context.cc",
+    "inline_pass_context.h",
   ]
 
   public_deps = [