Render advanced blends

Fix validation failures

Allow for multiple passes against the on screen target

Add fancy color wheel blend test

Tweak test

Fix compare URL

Improve comments

Author: bdero

impeller/aiks/aiks_context.cc

@@ -28,13 +28,13 @@ bool AiksContext::IsValid() const {
   return is_valid_;
 }
 
-bool AiksContext::Render(const Picture& picture, RenderPass& parent_pass) {
+bool AiksContext::Render(const Picture& picture, RenderTarget& render_target) {
   if (!IsValid()) {
     return false;
   }
 
   if (picture.pass) {
-    return picture.pass->Render(*content_context_, parent_pass);
+    return picture.pass->Render(*content_context_, render_target);
   }
 
   return true;

impeller/aiks/aiks_context.h

@@ -9,6 +9,7 @@
 #include "flutter/fml/macros.h"
 #include "impeller/entity/contents/content_context.h"
 #include "impeller/renderer/context.h"
+#include "impeller/renderer/render_target.h"
 
 namespace impeller {
 
@@ -23,7 +24,7 @@ class AiksContext {
 
   bool IsValid() const;
 
-  bool Render(const Picture& picture, RenderPass& parent_pass);
+  bool Render(const Picture& picture, RenderTarget& render_target);
 
  private:
   std::shared_ptr<Context> context_;

impeller/aiks/aiks_playground.cc

@@ -14,8 +14,8 @@ AiksPlayground::~AiksPlayground() = default;
 
 bool AiksPlayground::OpenPlaygroundHere(const Picture& picture) {
   return OpenPlaygroundHere(
-      [&picture](AiksContext& renderer, RenderPass& pass) -> bool {
-        return renderer.Render(picture, pass);
+      [&picture](AiksContext& renderer, RenderTarget& render_target) -> bool {
+        return renderer.Render(picture, render_target);
       });
 }
 
@@ -31,8 +31,8 @@ bool AiksPlayground::OpenPlaygroundHere(AiksPlaygroundCallback callback) {
   }
 
   return Playground::OpenPlaygroundHere(
-      [&renderer, &callback](RenderPass& pass) -> bool {
-        return callback(renderer, pass);
+      [&renderer, &callback](RenderTarget& render_target) -> bool {
+        return callback(renderer, render_target);
       });
 }
 

impeller/aiks/aiks_playground.h

@@ -14,7 +14,7 @@ namespace impeller {
 class AiksPlayground : public Playground {
  public:
   using AiksPlaygroundCallback =
-      std::function<bool(AiksContext& renderer, RenderPass& pass)>;
+      std::function<bool(AiksContext& renderer, RenderTarget& render_target)>;
 
   AiksPlayground();
 

impeller/aiks/aiks_unittests.cc

@@ -3,6 +3,8 @@
 // found in the LICENSE file.
 
 #include <array>
+#include <cmath>
+#include <tuple>
 
 #include "flutter/testing/testing.h"
 #include "impeller/aiks/aiks_playground.h"
@@ -467,6 +469,121 @@ TEST_P(AiksTest, PaintBlendModeIsRespected) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+TEST_P(AiksTest, CanDrawWithAdvancedBlend) {
+  // Compare with https://fiddle.skia.org/c/@BlendModes
+
+  std::vector<const char*> blend_mode_names;
+  std::vector<Entity::BlendMode> blend_mode_values;
+  {
+    const std::vector<std::tuple<const char*, Entity::BlendMode>> blends = {
+        // Pipeline blends (Porter-Duff/alpha blends)
+        {"Clear", Entity::BlendMode::kClear},
+        {"Source", Entity::BlendMode::kSource},
+        {"Destination", Entity::BlendMode::kDestination},
+        {"SourceOver", Entity::BlendMode::kSourceOver},
+        {"DestinationOver", Entity::BlendMode::kDestinationOver},
+        {"SourceIn", Entity::BlendMode::kSourceIn},
+        {"DestinationIn", Entity::BlendMode::kDestinationIn},
+        {"SourceOut", Entity::BlendMode::kSourceOut},
+        {"DestinationOut", Entity::BlendMode::kDestinationOut},
+        {"SourceATop", Entity::BlendMode::kSourceATop},
+        {"DestinationATop", Entity::BlendMode::kDestinationATop},
+        {"Xor", Entity::BlendMode::kXor},
+        {"Plus", Entity::BlendMode::kPlus},
+        {"Modulate", Entity::BlendMode::kModulate},
+        // Advanced blends (non Porter-Duff/color blends)
+        {"Screen", Entity::BlendMode::kScreen},
+    };
+    assert(blends.size() ==
+           static_cast<size_t>(Entity::BlendMode::kLastAdvancedBlendMode) + 1);
+    for (const auto& [name, mode] : blends) {
+      blend_mode_names.push_back(name);
+      blend_mode_values.push_back(mode);
+    }
+  }
+
+  auto draw_color_wheel = [](Canvas& canvas) {
+    /// color_wheel_sampler: r=0 -> fuchsia, r=2pi/3 -> yellow, r=4pi/3 ->
+    /// cyan domain: r >= 0 (because modulo used is non euclidean)
+    auto color_wheel_sampler = [](Radians r) {
+      Scalar x = r.radians / k2Pi + 1;
+
+      // https://www.desmos.com/calculator/6nhjelyoaj
+      auto color_cycle = [](Scalar x) {
+        Scalar cycle = std::fmod(x, 6.0f);
+        return std::max(0.0f, std::min(1.0f, 2 - std::abs(2 - cycle)));
+      };
+      return Color(color_cycle(6 * x + 1),  //
+                   color_cycle(6 * x - 1),  //
+                   color_cycle(6 * x - 3),  //
+                   1);
+    };
+
+    Paint paint;
+
+    // Draw a fancy color wheel for the backdrop.
+    // https://www.desmos.com/calculator/xw7kafthwd
+    const int max_dist = 900;
+    for (int i = 0; i <= 900; i++) {
+      Radians r(kPhi / k2Pi * i);
+      Scalar distance = r.radians / std::powf(4.12, 0.0026 * r.radians);
+      Scalar normalized_distance = static_cast<Scalar>(i) / max_dist;
+
+      paint.color =
+          color_wheel_sampler(r).WithAlpha(1.0f - normalized_distance);
+      Point position(distance * std::sin(r.radians),
+                     -distance * std::cos(r.radians));
+
+      canvas.DrawCircle(position, 9 + normalized_distance * 3, paint);
+    }
+  };
+
+  bool first_frame = true;
+  auto callback = [&](AiksContext& renderer, RenderTarget& render_target) {
+    if (first_frame) {
+      first_frame = false;
+      ImGui::SetNextWindowSize({350, 200});
+      ImGui::SetNextWindowPos({325, 550});
+    }
+
+    ImGui::Begin("Controls");
+    static int current_blend_index = 3;
+    ImGui::ListBox("Blending mode", &current_blend_index,
+                   blend_mode_names.data(), blend_mode_names.size());
+    ImGui::End();
+
+    Canvas canvas;
+    Paint paint;
+    // Default blend is kSourceOver.
+    paint.color = Color::White();
+    canvas.DrawPaint(paint);
+
+    canvas.Translate(Vector2(500, 400));
+    canvas.Scale(Vector2(3, 3));
+
+    draw_color_wheel(canvas);
+
+    // Draw 3 circles to a subpass and blend it in.
+    canvas.SaveLayer({.blend_mode = blend_mode_values[current_blend_index]});
+    {
+      paint.blend_mode = Entity::BlendMode::kPlus;
+      const Scalar x = std::sin(k2Pi / 3);
+      const Scalar y = -std::cos(k2Pi / 3);
+      paint.color = Color::Red();
+      canvas.DrawCircle(Point(-x, y) * 45, 65, paint);
+      paint.color = Color::Green();
+      canvas.DrawCircle(Point(0, -1) * 45, 65, paint);
+      paint.color = Color::Blue();
+      canvas.DrawCircle(Point(x, y) * 45, 65, paint);
+    }
+    canvas.Restore();
+
+    return renderer.Render(canvas.EndRecordingAsPicture(), render_target);
+  };
+
+  ASSERT_TRUE(OpenPlaygroundHere(callback));
+}
+
 TEST_P(AiksTest, TransformMultipliesCorrectly) {
   Canvas canvas;
   ASSERT_MATRIX_NEAR(canvas.GetCurrentTransformation(), Matrix());
@@ -509,7 +626,7 @@ TEST_P(AiksTest, TransformMultipliesCorrectly) {
 TEST_P(AiksTest, SolidStrokesRenderCorrectly) {
   // Compare with https://fiddle.skia.org/c/027392122bec8ac2b5d5de00a4b9bbe2
   bool first_frame = true;
-  auto callback = [&](AiksContext& renderer, RenderPass& pass) {
+  auto callback = [&](AiksContext& renderer, RenderTarget& render_target) {
     if (first_frame) {
       first_frame = false;
       ImGui::SetNextWindowSize({480, 100});
@@ -573,14 +690,14 @@ TEST_P(AiksTest, SolidStrokesRenderCorrectly) {
       canvas.Translate({-240, 60});
     }
 
-    return renderer.Render(canvas.EndRecordingAsPicture(), pass);
+    return renderer.Render(canvas.EndRecordingAsPicture(), render_target);
   };
 
   ASSERT_TRUE(OpenPlaygroundHere(callback));
 }
 
 TEST_P(AiksTest, CoverageOriginShouldBeAccountedForInSubpasses) {
-  auto callback = [](AiksContext& renderer, RenderPass& pass) {
+  auto callback = [](AiksContext& renderer, RenderTarget& render_target) {
     Canvas canvas;
     Paint alpha;
     alpha.color = Color::Red().WithAlpha(0.5);
@@ -605,7 +722,7 @@ TEST_P(AiksTest, CoverageOriginShouldBeAccountedForInSubpasses) {
 
     canvas.Restore();
 
-    return renderer.Render(canvas.EndRecordingAsPicture(), pass);
+    return renderer.Render(canvas.EndRecordingAsPicture(), render_target);
   };
 
   ASSERT_TRUE(OpenPlaygroundHere(callback));

impeller/display_list/display_list_playground.cc

@@ -36,14 +36,14 @@ bool DisplayListPlayground::OpenPlaygroundHere(
     return false;
   }
   return Playground::OpenPlaygroundHere(
-      [&context, &callback](RenderPass& pass) -> bool {
+      [&context, &callback](RenderTarget& render_target) -> bool {
         auto list = callback();
 
         DisplayListDispatcher dispatcher;
         list->Dispatch(dispatcher);
         auto picture = dispatcher.EndRecordingAsPicture();
 
-        return context.Render(picture, pass);
+        return context.Render(picture, render_target);
       });
 }
 

impeller/entity/contents/content_context.cc

@@ -7,6 +7,7 @@
 #include <sstream>
 
 #include "impeller/renderer/command_buffer.h"
+#include "impeller/renderer/formats.h"
 #include "impeller/renderer/render_pass.h"
 #include "impeller/renderer/render_target.h"
 

impeller/entity/contents/filters/inputs/texture_filter_input.cc

@@ -27,9 +27,4 @@ std::optional<Rect> TextureFilterInput::GetCoverage(
       .TransformBounds(GetTransform(entity));
 }
 
-Matrix TextureFilterInput::GetLocalTransform(const Entity& entity) const {
-  // Compute the local transform such that the texture is centered.
-  return Matrix::MakeTranslation(-Point(texture_->GetSize()) / 2);
-}
-
 }  // namespace impeller

impeller/entity/contents/filters/inputs/texture_filter_input.h

@@ -22,9 +22,6 @@ class TextureFilterInput final : public FilterInput {
   // |FilterInput|
   std::optional<Rect> GetCoverage(const Entity& entity) const override;
 
-  // |FilterInput|
-  Matrix GetLocalTransform(const Entity& entity) const override;
-
  private:
   TextureFilterInput(std::shared_ptr<Texture> texture);
 

impeller/entity/entity.cc

@@ -8,6 +8,7 @@
 
 #include "impeller/base/validation.h"
 #include "impeller/entity/contents/content_context.h"
+#include "impeller/entity/contents/filters/filter_contents.h"
 #include "impeller/renderer/render_pass.h"
 
 namespace impeller {
@@ -61,10 +62,6 @@ void Entity::IncrementStencilDepth(uint32_t increment) {
 }
 
 void Entity::SetBlendMode(BlendMode blend_mode) {
-  if (blend_mode_ > BlendMode::kLastPipelineBlendMode) {
-    VALIDATION_LOG << "Non-pipeline blend modes are not supported by the "
-                      "entity blend mode setting.";
-  }
   blend_mode_ = blend_mode;
 }