aiks_dl_blend_unittests.cc

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#include <memory>
 
#include "display_list/display_list.h"
#include "display_list/dl_sampling_options.h"
#include "display_list/dl_tile_mode.h"
#include "display_list/effects/dl_color_filter.h"
#include "display_list/effects/dl_color_source.h"
#include "display_list/effects/dl_mask_filter.h"
#include "flutter/impeller/display_list/aiks_unittests.h"
 
#include "flutter/display_list/dl_blend_mode.h"
#include "flutter/display_list/dl_builder.h"
#include "flutter/display_list/dl_color.h"
#include "flutter/display_list/dl_paint.h"
#include "flutter/impeller/display_list/dl_image_impeller.h"
#include "flutter/impeller/geometry/scalar.h"
#include "impeller/display_list/aiks_context.h"
#include "impeller/display_list/dl_dispatcher.h"
#include "impeller/playground/playground.h"
#include "impeller/playground/playground_test.h"
#include "impeller/renderer/testing/mocks.h"
 
////////////////////////////////////////////////////////////////////////////////
// This is for tests of Canvas that are interested the results of rendering
// blends.
////////////////////////////////////////////////////////////////////////////////
 
namespace impeller {
namespace testing {
 
using namespace flutter;
 
#define BLEND_MODE_TUPLE(blend_mode) {#blend_mode, BlendMode::k##blend_mode},
 
struct BlendModeSelection {
  std::vector<const char*> blend_mode_names;
  std::vector<BlendMode> blend_mode_values;
};
 
static BlendModeSelection GetBlendModeSelection() {
  std::vector<const char*> blend_mode_names;
  std::vector<BlendMode> blend_mode_values;
  {
    const std::vector<std::tuple<const char*, BlendMode>> blends = {
        IMPELLER_FOR_EACH_BLEND_MODE(BLEND_MODE_TUPLE)};
    assert(blends.size() ==
           static_cast<size_t>(Entity::kLastAdvancedBlendMode) + 1);
    for (const auto& [name, mode] : blends) {
      blend_mode_names.push_back(name);
      blend_mode_values.push_back(mode);
    }
  }
 
  return {blend_mode_names, blend_mode_values};
}
 
TEST_P(AiksTest, CanRenderAdvancedBlendColorFilterWithSaveLayer) {
  DisplayListBuilder builder;
 
  DlRect layer_rect = DlRect::MakeXYWH(0, 0, 500, 500);
  builder.ClipRect(layer_rect);
 
  DlPaint save_paint;
  save_paint.setColorFilter(DlColorFilter::MakeBlend(
      DlColor::RGBA(0, 1, 0, 0.5), DlBlendMode::kDifference));
  builder.SaveLayer(layer_rect, &save_paint);
 
  DlPaint paint;
  paint.setColor(DlColor::kBlack());
  builder.DrawPaint(paint);
  paint.setColor(DlColor::kWhite());
  builder.DrawRect(DlRect::MakeXYWH(100, 100, 300, 300), paint);
  builder.Restore();
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, BlendModeShouldCoverWholeScreen) {
  DisplayListBuilder builder;
  DlPaint paint;
 
  paint.setColor(DlColor::kRed());
  builder.DrawPaint(paint);
 
  paint.setBlendMode(DlBlendMode::kSrcOver);
  builder.SaveLayer(std::nullopt, &paint);
 
  paint.setColor(DlColor::kWhite());
  builder.DrawRect(DlRect::MakeXYWH(100, 100, 400, 400), paint);
 
  paint.setBlendMode(DlBlendMode::kSrc);
  builder.SaveLayer(std::nullopt, &paint);
 
  paint.setColor(DlColor::kBlue());
  builder.DrawRect(DlRect::MakeXYWH(200, 200, 200, 200), paint);
 
  builder.Restore();
  builder.Restore();
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, CanDrawPaintWithAdvancedBlend) {
  DisplayListBuilder builder;
 
  builder.Scale(0.2, 0.2);
  DlPaint paint;
  paint.setColor(DlColor::RGBA(
      Color::MediumTurquoise().red, Color::MediumTurquoise().green,
      Color::MediumTurquoise().blue, Color::MediumTurquoise().alpha));
  builder.DrawPaint(paint);
 
  paint.setColor(DlColor::RGBA(Color::OrangeRed().red, Color::OrangeRed().green,
                               Color::OrangeRed().blue, 0.5));
  paint.setBlendMode(DlBlendMode::kHue);
  builder.DrawPaint(paint);
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, DrawPaintWithAdvancedBlendOverFilter) {
  DlPaint paint;
  paint.setColor(DlColor::kBlack());
  paint.setMaskFilter(DlBlurMaskFilter::Make(DlBlurStyle::kNormal, 60));
 
  DisplayListBuilder builder;
  paint.setColor(DlColor::kWhite());
  builder.DrawPaint(paint);
  paint.setColor(DlColor::kBlack());
  builder.DrawCircle(DlPoint(300, 300), 200, paint);
  paint.setColor(DlColor::kGreen());
  paint.setBlendMode(DlBlendMode::kScreen);
  builder.DrawPaint(paint);
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, DrawAdvancedBlendPartlyOffscreen) {
  DisplayListBuilder builder;
 
  DlPaint draw_paint;
  draw_paint.setColor(DlColor::kBlue());
  builder.DrawPaint(draw_paint);
  builder.Scale(2, 2);
  builder.ClipRect(DlRect::MakeLTRB(0, 0, 200, 200));
 
  std::vector<DlColor> colors = {DlColor::RGBA(0.9568, 0.2627, 0.2118, 1.0),
                                 DlColor::RGBA(0.1294, 0.5882, 0.9529, 1.0)};
  std::vector<Scalar> stops = {0.0, 1.0};
 
  DlPaint paint;
  DlMatrix matrix = DlMatrix::MakeScale({0.3, 0.3, 1.0});
  paint.setColorSource(DlColorSource::MakeLinear(
      /*start_point=*/{0, 0},             //
      /*end_point=*/{100, 100},           //
      /*stop_count=*/colors.size(),       //
      /*colors=*/colors.data(),           //
      /*stops=*/stops.data(),             //
      /*tile_mode=*/DlTileMode::kRepeat,  //
      /*matrix=*/&matrix                  //
      ));
  paint.setBlendMode(DlBlendMode::kLighten);
 
  builder.DrawCircle(DlPoint(100, 100), 100, paint);
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, PaintBlendModeIsRespected) {
  DlPaint paint;
  DisplayListBuilder builder;
  // Default is kSourceOver.
 
  paint.setColor(DlColor::RGBA(1, 0, 0, 0.5));
  builder.DrawCircle(DlPoint(150, 200), 100, paint);
 
  paint.setColor(DlColor::RGBA(0, 1, 0, 0.5));
  builder.DrawCircle(DlPoint(250, 200), 100, paint);
 
  paint.setBlendMode(DlBlendMode::kPlus);
 
  paint.setColor(DlColor::kRed());
  builder.DrawCircle(DlPoint(450, 250), 100, paint);
 
  paint.setColor(DlColor::kGreen());
  builder.DrawCircle(DlPoint(550, 250), 100, paint);
 
  paint.setColor(DlColor::kBlue());
  builder.DrawCircle(DlPoint(500, 150), 100, paint);
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
// Compare results with https://api.flutter.dev/flutter/dart-ui/BlendMode.html
TEST_P(AiksTest, ColorFilterBlend) {
  bool has_color_filter = true;
  auto callback = [&]() -> sk_sp<DisplayList> {
    if (AiksTest::ImGuiBegin("Controls", nullptr,
                             ImGuiWindowFlags_AlwaysAutoResize)) {
      ImGui::Checkbox("has color filter", &has_color_filter);
      ImGui::End();
    }
 
    DisplayListBuilder builder;
    builder.Scale(GetContentScale().x, GetContentScale().y);
 
    auto src_image =
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_src.png"));
    auto dst_image =
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_dst.png"));
 
    std::vector<DlBlendMode> blend_modes = {
        DlBlendMode::kSrc,     DlBlendMode::kSrcATop, DlBlendMode::kSrcOver,
        DlBlendMode::kSrcIn,   DlBlendMode::kSrcOut,  DlBlendMode::kDst,
        DlBlendMode::kDstATop, DlBlendMode::kDstOver, DlBlendMode::kDstIn,
        DlBlendMode::kDstOut,  DlBlendMode::kClear,   DlBlendMode::kXor};
 
    for (uint32_t i = 0; i < blend_modes.size(); ++i) {
      builder.Save();
      builder.Translate((i % 5) * 200, (i / 5) * 200);
      builder.Scale(0.4, 0.4);
      {
        DlPaint dstPaint;
        builder.DrawImage(dst_image, DlPoint(0, 0),
                          DlImageSampling::kMipmapLinear, &dstPaint);
      }
      {
        DlPaint srcPaint;
        srcPaint.setBlendMode(blend_modes[i]);
        if (has_color_filter) {
          std::shared_ptr<const DlColorFilter> color_filter =
              DlColorFilter::MakeBlend(DlColor::RGBA(0.9, 0.5, 0.0, 1.0),
                                       DlBlendMode::kSrcIn);
          srcPaint.setColorFilter(color_filter);
        }
        builder.DrawImage(src_image, DlPoint(0, 0),
                          DlImageSampling::kMipmapLinear, &srcPaint);
      }
      builder.Restore();
    }
    return builder.Build();
  };
  ASSERT_TRUE(OpenPlaygroundHere(callback));
}
 
// Verification for: https://github.com/flutter/flutter/issues/155691
TEST_P(AiksTest, ColorFilterAdvancedBlend) {
  bool has_color_filter = true;
  auto callback = [&]() -> sk_sp<DisplayList> {
    if (AiksTest::ImGuiBegin("Controls", nullptr,
                             ImGuiWindowFlags_AlwaysAutoResize)) {
      ImGui::Checkbox("has color filter", &has_color_filter);
      ImGui::End();
    }
 
    DisplayListBuilder builder;
    builder.Scale(GetContentScale().x, GetContentScale().y);
 
    auto src_image =
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_src.png"));
    auto dst_image =
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_dst.png"));
 
    std::vector<DlBlendMode> blend_modes = {
        DlBlendMode::kScreen,     DlBlendMode::kOverlay,
        DlBlendMode::kDarken,     DlBlendMode::kLighten,
        DlBlendMode::kColorDodge, DlBlendMode::kColorBurn,
        DlBlendMode::kHardLight,  DlBlendMode::kSoftLight,
        DlBlendMode::kDifference, DlBlendMode::kExclusion,
        DlBlendMode::kMultiply,   DlBlendMode::kHue,
        DlBlendMode::kSaturation, DlBlendMode::kColor,
        DlBlendMode::kLuminosity,
    };
 
    for (uint32_t i = 0; i < blend_modes.size(); ++i) {
      builder.Save();
      builder.Translate((i % 5) * 200, (i / 5) * 200);
      builder.Scale(0.4, 0.4);
      {
        DlPaint dstPaint;
        builder.DrawImage(dst_image, DlPoint(0, 0),
                          DlImageSampling::kMipmapLinear, &dstPaint);
      }
      {
        DlPaint srcPaint;
        srcPaint.setBlendMode(blend_modes[i]);
        if (has_color_filter) {
          std::shared_ptr<const DlColorFilter> color_filter =
              DlColorFilter::MakeBlend(DlColor::RGBA(0.9, 0.5, 0.0, 1.0),
                                       DlBlendMode::kSrcIn);
          srcPaint.setColorFilter(color_filter);
        }
        builder.DrawImage(src_image, DlPoint(0, 0),
                          DlImageSampling::kMipmapLinear, &srcPaint);
      }
      builder.Restore();
    }
    return builder.Build();
  };
  ASSERT_TRUE(OpenPlaygroundHere(callback));
}
 
// Variant of the https://github.com/flutter/flutter/issues/155691 test that
// uses an advanced blend in the color filter and disables framebuffer fetch
// to force usage of BlendFilterContents::CreateForegroundAdvancedBlend.
TEST_P(AiksTest, ColorFilterAdvancedBlendNoFbFetch) {
  if (GetParam() != PlaygroundBackend::kMetal) {
    GTEST_SKIP()
        << "This backend doesn't yet support setting device capabilities.";
  }
  if (!WillRenderSomething()) {
    GTEST_SKIP() << "This test requires playgrounds.";
  }
 
  std::shared_ptr<const Capabilities> old_capabilities =
      GetContext()->GetCapabilities();
  auto mock_capabilities = std::make_shared<MockCapabilities>();
  EXPECT_CALL(*mock_capabilities, SupportsFramebufferFetch())
      .Times(::testing::AtLeast(1))
      .WillRepeatedly(::testing::Return(false));
  FLT_FORWARD(mock_capabilities, old_capabilities, GetDefaultColorFormat);
  FLT_FORWARD(mock_capabilities, old_capabilities, GetDefaultStencilFormat);
  FLT_FORWARD(mock_capabilities, old_capabilities,
              GetDefaultDepthStencilFormat);
  FLT_FORWARD(mock_capabilities, old_capabilities, SupportsOffscreenMSAA);
  FLT_FORWARD(mock_capabilities, old_capabilities,
              SupportsImplicitResolvingMSAA);
  FLT_FORWARD(mock_capabilities, old_capabilities, SupportsReadFromResolve);
  FLT_FORWARD(mock_capabilities, old_capabilities, SupportsSSBO);
  FLT_FORWARD(mock_capabilities, old_capabilities, SupportsCompute);
  FLT_FORWARD(mock_capabilities, old_capabilities,
              SupportsTextureToTextureBlits);
  FLT_FORWARD(mock_capabilities, old_capabilities, GetDefaultGlyphAtlasFormat);
  FLT_FORWARD(mock_capabilities, old_capabilities, SupportsTriangleFan);
  FLT_FORWARD(mock_capabilities, old_capabilities,
              SupportsDecalSamplerAddressMode);
  FLT_FORWARD(mock_capabilities, old_capabilities, SupportsPrimitiveRestart);
  FLT_FORWARD(mock_capabilities, old_capabilities, GetMinimumUniformAlignment);
  ASSERT_TRUE(SetCapabilities(mock_capabilities).ok());
 
  bool has_color_filter = true;
  auto callback = [&]() -> sk_sp<DisplayList> {
    if (AiksTest::ImGuiBegin("Controls", nullptr,
                             ImGuiWindowFlags_AlwaysAutoResize)) {
      ImGui::Checkbox("has color filter", &has_color_filter);
      ImGui::End();
    }
 
    DisplayListBuilder builder;
    builder.Scale(GetContentScale().x, GetContentScale().y);
 
    auto src_image =
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_src.png"));
    auto dst_image =
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_dst.png"));
 
    std::vector<DlBlendMode> blend_modes = {
        DlBlendMode::kScreen,     DlBlendMode::kOverlay,
        DlBlendMode::kDarken,     DlBlendMode::kLighten,
        DlBlendMode::kColorDodge, DlBlendMode::kColorBurn,
        DlBlendMode::kHardLight,  DlBlendMode::kSoftLight,
        DlBlendMode::kDifference, DlBlendMode::kExclusion,
        DlBlendMode::kMultiply,   DlBlendMode::kHue,
        DlBlendMode::kSaturation, DlBlendMode::kColor,
        DlBlendMode::kLuminosity,
    };
 
    for (uint32_t i = 0; i < blend_modes.size(); ++i) {
      builder.Save();
      builder.Translate((i % 5) * 200, (i / 5) * 200);
      builder.Scale(0.4, 0.4);
      {
        DlPaint dstPaint;
        builder.DrawImage(dst_image, DlPoint(0, 0),
                          DlImageSampling::kMipmapLinear, &dstPaint);
      }
      {
        DlPaint srcPaint;
        srcPaint.setBlendMode(blend_modes[i]);
        if (has_color_filter) {
          std::shared_ptr<const DlColorFilter> color_filter =
              DlColorFilter::MakeBlend(DlColor::RGBA(0.9, 0.5, 0.0, 1.0),
                                       DlBlendMode::kMultiply);
          srcPaint.setColorFilter(color_filter);
        }
        builder.DrawImage(src_image, DlPoint(0, 0),
                          DlImageSampling::kMipmapLinear, &srcPaint);
      }
      builder.Restore();
    }
    return builder.Build();
  };
  ASSERT_TRUE(OpenPlaygroundHere(callback));
}
 
// Bug: https://github.com/flutter/flutter/issues/142549
TEST_P(AiksTest, BlendModePlusAlphaWideGamut) {
  // Must be called before any methods that use the context to ensure that
  // this test is always run with wide gamut support.
  if (!EnsureContextSupportsWideGamut()) {
    GTEST_SKIP() << "This backend doesn't yet support wide gamut.";
  }
 
  EXPECT_EQ(GetContext()->GetCapabilities()->GetDefaultColorFormat(),
            PixelFormat::kB10G10R10A10XR);
  auto texture = CreateTextureForFixture("airplane.jpg",
                                         /*enable_mipmapping=*/true);
 
  DisplayListBuilder builder;
  DlPaint paint;
  builder.Scale(GetContentScale().x, GetContentScale().y);
 
  paint.setColor(DlColor::RGBA(0.9, 1, 0.9, 1.0));
  builder.DrawPaint(paint);
  builder.SaveLayer(std::nullopt);
 
  paint.setBlendMode(DlBlendMode::kPlus);
  paint.setColor(DlColor::kRed());
 
  builder.DrawRect(DlRect::MakeXYWH(100, 100, 400, 400), paint);
  paint.setColor(DlColor::kWhite());
 
  auto rect = Rect::MakeXYWH(100, 100, 400, 400).Expand(-100, -100);
  builder.DrawImageRect(
      DlImageImpeller::Make(texture),
      DlRect::MakeWH(texture->GetSize().width, texture->GetSize().height),
      DlRect::MakeLTRB(rect.GetLeft(), rect.GetTop(),  //
                       rect.GetRight(), rect.GetBottom()),
      DlImageSampling::kMipmapLinear, &paint);
  builder.Restore();
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
// Bug: https://github.com/flutter/flutter/issues/142549
TEST_P(AiksTest, BlendModePlusAlphaColorFilterWideGamut) {
  // Must be called before any methods that use the context to ensure that
  // this test is always run with wide gamut support.
  if (!EnsureContextSupportsWideGamut()) {
    GTEST_SKIP() << "This backend doesn't yet support wide gamut.";
  }
 
  EXPECT_EQ(GetContext()->GetCapabilities()->GetDefaultColorFormat(),
            PixelFormat::kB10G10R10A10XR);
  auto texture = CreateTextureForFixture("airplane.jpg",
                                         /*enable_mipmapping=*/true);
 
  DisplayListBuilder builder;
  builder.Scale(GetContentScale().x, GetContentScale().y);
 
  DlPaint paint;
  paint.setColor(DlColor::RGBA(0.1, 0.2, 0.1, 1.0));
  builder.DrawPaint(paint);
 
  DlPaint save_paint;
  save_paint.setColorFilter(
      DlColorFilter::MakeBlend(DlColor::RGBA(1, 0, 0, 1), DlBlendMode::kPlus));
  builder.SaveLayer(std::nullopt, &save_paint);
 
  paint.setColor(DlColor::kRed());
  builder.DrawRect(DlRect::MakeXYWH(100, 100, 400, 400), paint);
 
  paint.setColor(DlColor::kWhite());
 
  auto rect = Rect::MakeXYWH(100, 100, 400, 400).Expand(-100, -100);
  builder.DrawImageRect(
      DlImageImpeller::Make(texture),
      DlRect::MakeWH(texture->GetSize().width, texture->GetSize().height),
      DlRect::MakeLTRB(rect.GetLeft(), rect.GetTop(),  //
                       rect.GetRight(), rect.GetBottom()),
      DlImageSampling::kMipmapLinear, &paint);
  builder.Restore();
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, ForegroundBlendSubpassCollapseOptimization) {
  DisplayListBuilder builder;
 
  DlPaint save_paint;
  save_paint.setColorFilter(
      DlColorFilter::MakeBlend(DlColor::kRed(), DlBlendMode::kColorDodge));
  builder.SaveLayer(std::nullopt, &save_paint);
 
  builder.Translate(500, 300);
  builder.Rotate(120);
 
  DlPaint paint;
  paint.setColor(DlColor::kBlue());
  builder.DrawRect(DlRect::MakeXYWH(100, 100, 200, 200), paint);
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, ClearBlend) {
  DisplayListBuilder builder;
 
  DlPaint blue;
  blue.setColor(DlColor::kBlue());
  builder.DrawRect(DlRect::MakeXYWH(0, 0, 600.0, 600.0), blue);
 
  DlPaint clear;
  clear.setBlendMode(DlBlendMode::kClear);
 
  builder.DrawCircle(DlPoint(300.0, 300.0), 200.0, clear);
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
static sk_sp<DisplayList> BlendModeTest(Vector2 content_scale,
                                        BlendMode blend_mode,
                                        const sk_sp<DlImageImpeller>& src_image,
                                        const sk_sp<DlImageImpeller>& dst_image,
                                        Scalar src_alpha) {
  if (AiksTest::ImGuiBegin("Controls", nullptr,
                           ImGuiWindowFlags_AlwaysAutoResize)) {
    ImGui::SliderFloat("Source alpha", &src_alpha, 0, 1);
    ImGui::End();
  }
 
  Color destination_color = Color::CornflowerBlue().WithAlpha(0.75);
  auto source_colors = std::vector<Color>({Color::White().WithAlpha(0.75),
                                           Color::LimeGreen().WithAlpha(0.75),
                                           Color::Black().WithAlpha(0.75)});
 
  DisplayListBuilder builder;
  {
    DlPaint paint;
    paint.setColor(DlColor::kBlack());
    builder.DrawPaint(paint);
  }
  // TODO(bdero): Why does this cause the left image to double scale on high DPI
  //              displays.
  // builder.Scale(content_scale);
 
  //----------------------------------------------------------------------------
  /// 1. Save layer blending (top squares).
  ///
 
  builder.Save();
  for (const auto& color : source_colors) {
    builder.Save();
    {
      builder.ClipRect(DlRect::MakeXYWH(25, 25, 100, 100));
      // Perform the blend in a SaveLayer so that the initial backdrop color is
      // fully transparent black. SourceOver blend the result onto the parent
      // pass.
      builder.SaveLayer(std::nullopt);
      {
        DlPaint draw_paint;
        draw_paint.setColor(
            DlColor::RGBA(destination_color.red, destination_color.green,
                          destination_color.blue, destination_color.alpha));
        builder.DrawPaint(draw_paint);
 
        // Draw the source color in an offscreen pass and blend it to the parent
        // pass.
        DlPaint save_paint;
        save_paint.setBlendMode(static_cast<DlBlendMode>(blend_mode));
        builder.SaveLayer(std::nullopt, &save_paint);
        {  //
          DlPaint paint;
          paint.setColor(
              DlColor::RGBA(color.red, color.green, color.blue, color.alpha));
          builder.DrawRect(DlRect::MakeXYWH(25, 25, 100, 100), paint);
        }
        builder.Restore();
      }
      builder.Restore();
    }
    builder.Restore();
    builder.Translate(100, 0);
  }
  builder.RestoreToCount(0);
 
  //----------------------------------------------------------------------------
  /// 2. CPU blend modes (bottom squares).
  ///
 
  builder.Save();
  builder.Translate(0, 100);
  // Perform the blend in a SaveLayer so that the initial backdrop color is
  // fully transparent black. SourceOver blend the result onto the parent pass.
  builder.SaveLayer(std::nullopt);
  for (const auto& color : source_colors) {
    // Simply write the CPU blended color to the pass.
    DlPaint paint;
    auto dest = destination_color.Blend(color, blend_mode);
    paint.setColor(DlColor::RGBA(dest.red, dest.green, dest.blue, dest.alpha));
    paint.setBlendMode(DlBlendMode::kSrcOver);
    builder.DrawRect(DlRect::MakeXYWH(25, 25, 100, 100), paint);
    builder.Translate(100, 0);
  }
  builder.Restore();
  builder.Restore();
 
  //----------------------------------------------------------------------------
  /// 3. Image blending (bottom images).
  ///
  /// Compare these results with the images in the Flutter blend mode
  /// documentation: https://api.flutter.dev/flutter/dart-ui/BlendMode.html
  ///
 
  builder.Translate(0, 250);
 
  // Draw grid behind the images.
  {
    DlPaint paint;
    paint.setColor(DlColor::RGBA(41 / 255.0, 41 / 255.0, 41 / 255.0, 1));
    builder.DrawRect(DlRect::MakeLTRB(0, 0, 800, 400), paint);
  }
 
  DlPaint square_paint;
  square_paint.setColor(DlColor::RGBA(15 / 255.0, 15 / 255.0, 15 / 255.0, 1));
  for (int y = 0; y < 400 / 8; y++) {
    for (int x = 0; x < 800 / 16; x++) {
      builder.DrawRect(DlRect::MakeXYWH(x * 16 + (y % 2) * 8, y * 8, 8, 8),
                       square_paint);
    }
  }
 
  // Uploaded image source (left image).
  DlPaint paint;
  paint.setBlendMode(DlBlendMode::kSrcOver);
  builder.Save();
  builder.SaveLayer(std::nullopt, &paint);
  {
    builder.DrawImage(dst_image, DlPoint(0, 0), DlImageSampling::kMipmapLinear,
                      &paint);
 
    paint.setColor(DlColor::kWhite().withAlpha(src_alpha * 255));
    paint.setBlendMode(static_cast<DlBlendMode>(blend_mode));
    builder.DrawImage(src_image, DlPoint(0, 0), DlImageSampling::kMipmapLinear,
                      &paint);
  }
  builder.Restore();
  builder.Restore();
 
  // Rendered image source (right image).
  builder.Save();
 
  DlPaint save_paint;
  builder.SaveLayer(std::nullopt, &save_paint);
  {
    builder.DrawImage(dst_image, DlPoint(400, 0),
                      DlImageSampling::kMipmapLinear, nullptr);
 
    DlPaint save_paint;
    save_paint.setColor(DlColor::kWhite().withAlpha(src_alpha * 255));
    save_paint.setBlendMode(static_cast<DlBlendMode>(blend_mode));
    builder.SaveLayer(std::nullopt, &save_paint);
    {
      builder.DrawImage(src_image, DlPoint(400, 0),
                        DlImageSampling::kMipmapLinear, nullptr);
    }
    builder.Restore();
  }
  builder.Restore();
  builder.Restore();
 
  return builder.Build();
}
 
#define BLEND_MODE_TEST(blend_mode)                                           \
  TEST_P(AiksTest, BlendMode##blend_mode) {                                   \
    auto src_image =                                                          \
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_src.png")); \
    auto dst_image =                                                          \
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_dst.png")); \
    auto callback = [&]() -> sk_sp<DisplayList> {                             \
      return BlendModeTest(GetContentScale(), BlendMode::k##blend_mode,       \
                           src_image, dst_image, /*src_alpha=*/1.0);          \
    };                                                                        \
    OpenPlaygroundHere(callback);                                             \
  }
IMPELLER_FOR_EACH_BLEND_MODE(BLEND_MODE_TEST)
 
#define BLEND_MODE_SRC_ALPHA_TEST(blend_mode)                                 \
  TEST_P(AiksTest, BlendModeSrcAlpha##blend_mode) {                           \
    auto src_image =                                                          \
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_src.png")); \
    auto dst_image =                                                          \
        DlImageImpeller::Make(CreateTextureForFixture("blend_mode_dst.png")); \
    auto callback = [&]() -> sk_sp<DisplayList> {                             \
      return BlendModeTest(GetContentScale(), BlendMode::k##blend_mode,       \
                           src_image, dst_image, /*src_alpha=*/0.5);          \
    };                                                                        \
    OpenPlaygroundHere(callback);                                             \
  }
IMPELLER_FOR_EACH_BLEND_MODE(BLEND_MODE_SRC_ALPHA_TEST)
 
TEST_P(AiksTest, CanDrawPaintMultipleTimesInteractive) {
  auto modes = GetBlendModeSelection();
 
  auto callback = [&]() -> sk_sp<DisplayList> {
    static Color background = Color::MediumTurquoise();
    static Color foreground = Color::Color::OrangeRed().WithAlpha(0.5);
    static int current_blend_index = 3;
 
    if (AiksTest::ImGuiBegin("Controls", nullptr,
                             ImGuiWindowFlags_AlwaysAutoResize)) {
      ImGui::ColorEdit4("Background", reinterpret_cast<float*>(&background));
      ImGui::ColorEdit4("Foreground", reinterpret_cast<float*>(&foreground));
      ImGui::ListBox("Blend mode", &current_blend_index,
                     modes.blend_mode_names.data(),
                     modes.blend_mode_names.size());
      ImGui::End();
    }
 
    DisplayListBuilder builder;
    builder.Scale(0.2, 0.2);
    DlPaint paint;
    paint.setColor(DlColor(background.ToARGB()));
    builder.DrawPaint(paint);
 
    paint.setColor(DlColor(foreground.ToARGB()));
    paint.setBlendMode(static_cast<DlBlendMode>(current_blend_index));
    builder.DrawPaint(paint);
    return builder.Build();
  };
  ASSERT_TRUE(OpenPlaygroundHere(callback));
}
 
TEST_P(AiksTest, ForegroundPipelineBlendAppliesTransformCorrectly) {
  auto texture = CreateTextureForFixture("airplane.jpg",
                                         /*enable_mipmapping=*/true);
 
  DisplayListBuilder builder;
  builder.Rotate(30);
 
  DlPaint image_paint;
  image_paint.setColorFilter(DlColorFilter::MakeBlend(
      DlColor::RGBA(255.0f / 255.0f, 165.0f / 255.0f, 0.0f / 255.0f, 1.0f),
      DlBlendMode::kSrcIn));
 
  builder.DrawImage(DlImageImpeller::Make(texture), DlPoint(200, 200),
                    DlImageSampling::kMipmapLinear, &image_paint);
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, ForegroundAdvancedBlendAppliesTransformCorrectly) {
  auto texture = CreateTextureForFixture("airplane.jpg",
                                         /*enable_mipmapping=*/true);
 
  DisplayListBuilder builder;
  builder.Rotate(30);
 
  DlPaint image_paint;
  image_paint.setColorFilter(DlColorFilter::MakeBlend(
      DlColor::RGBA(255.0f / 255.0f, 165.0f / 255.0f, 0.0f / 255.0f, 1.0f),
      DlBlendMode::kColorDodge));
 
  builder.DrawImage(DlImageImpeller::Make(texture), DlPoint(200, 200),
                    DlImageSampling::kMipmapLinear, &image_paint);
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, FramebufferAdvancedBlendCoverage) {
  auto texture = CreateTextureForFixture("airplane.jpg",
                                         /*enable_mipmapping=*/true);
 
  // Draw with an advanced blend that can use FramebufferBlendContents and
  // verify that the scale transform is correctly applied to the image.
  DisplayListBuilder builder;
 
  DlPaint paint;
  paint.setColor(
      DlColor::RGBA(169.0f / 255.0f, 169.0f / 255.0f, 169.0f / 255.0f, 1.0f));
  builder.DrawPaint(paint);
  builder.Scale(0.4, 0.4);
 
  DlPaint image_paint;
  image_paint.setBlendMode(DlBlendMode::kMultiply);
 
  builder.DrawImage(DlImageImpeller::Make(texture), DlPoint(20, 20),
                    DlImageSampling::kMipmapLinear, &image_paint);
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, ColorWheel) {
  // Compare with https://fiddle.skia.org/c/@BlendModes
 
  BlendModeSelection blend_modes = GetBlendModeSelection();
 
  auto draw_color_wheel = [](DisplayListBuilder& builder) -> void {
    /// 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);
    };
 
    DlPaint paint;
    paint.setBlendMode(DlBlendMode::kSrcOver);
 
    // 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;
 
      auto color = color_wheel_sampler(r).WithAlpha(1.0f - normalized_distance);
      paint.setColor(
          DlColor::RGBA(color.red, color.green, color.blue, color.alpha));
      DlPoint position = DlPoint(distance * std::sin(r.radians),
                                 -distance * std::cos(r.radians));
 
      builder.DrawCircle(position, 9 + normalized_distance * 3, paint);
    }
  };
 
  auto callback = [&]() -> sk_sp<DisplayList> {
    // UI state.
    static bool cache_the_wheel = true;
    static int current_blend_index = 3;
    static float dst_alpha = 1;
    static float src_alpha = 1;
    static DlColor color0 = DlColor::kRed();
    static DlColor color1 = DlColor::kGreen();
    static DlColor color2 = DlColor::kBlue();
 
    if (AiksTest::ImGuiBegin("Controls", nullptr,
                             ImGuiWindowFlags_AlwaysAutoResize)) {
      ImGui::Checkbox("Cache the wheel", &cache_the_wheel);
      ImGui::ListBox("Blending mode", &current_blend_index,
                     blend_modes.blend_mode_names.data(),
                     blend_modes.blend_mode_names.size());
      ImGui::SliderFloat("Source alpha", &src_alpha, 0, 1);
      ImGui::ColorEdit4("Color A", reinterpret_cast<float*>(&color0));
      ImGui::ColorEdit4("Color B", reinterpret_cast<float*>(&color1));
      ImGui::ColorEdit4("Color C", reinterpret_cast<float*>(&color2));
      ImGui::SliderFloat("Destination alpha", &dst_alpha, 0, 1);
      ImGui::End();
    }
 
    DisplayListBuilder builder;
 
    DlPaint paint;
    paint.setColor(DlColor::kWhite().withAlpha(dst_alpha * 255));
    paint.setBlendMode(DlBlendMode::kSrc);
    builder.SaveLayer(std::nullopt, &paint);
    {
      DlPaint paint;
      paint.setColor(DlColor::kWhite());
      builder.DrawPaint(paint);
 
      builder.SaveLayer(std::nullopt, nullptr);
      builder.Scale(GetContentScale().x, GetContentScale().y);
      builder.Translate(500, 400);
      builder.Scale(3, 3);
      draw_color_wheel(builder);
      builder.Restore();
    }
    builder.Restore();
 
    builder.Scale(GetContentScale().x, GetContentScale().y);
    builder.Translate(500, 400);
    builder.Scale(3, 3);
 
    // Draw 3 circles to a subpass and blend it in.
    DlPaint save_paint;
    save_paint.setColor(DlColor::kWhite().withAlpha(src_alpha * 255));
    save_paint.setBlendMode(static_cast<DlBlendMode>(
        blend_modes.blend_mode_values[current_blend_index]));
    builder.SaveLayer(std::nullopt, &save_paint);
    {
      DlPaint paint;
      paint.setBlendMode(DlBlendMode::kPlus);
      const Scalar x = std::sin(k2Pi / 3);
      const Scalar y = -std::cos(k2Pi / 3);
      paint.setColor(color0);
      builder.DrawCircle(DlPoint(-x * 45, y * 45), 65, paint);
      paint.setColor(color1);
      builder.DrawCircle(DlPoint(0, -45), 65, paint);
      paint.setColor(color2);
      builder.DrawCircle(DlPoint(x * 45, y * 45), 65, paint);
    }
    builder.Restore();
 
    return builder.Build();
  };
 
  ASSERT_TRUE(OpenPlaygroundHere(callback));
}
 
TEST_P(AiksTest, DestructiveBlendColorFilterFloodsClip) {
  DisplayListBuilder builder;
 
  DlPaint paint;
  paint.setColor(DlColor::kBlue());
  builder.DrawPaint(paint);
 
  DlPaint save_paint;
  save_paint.setColorFilter(
      DlColorFilter::MakeBlend(DlColor::kRed(), DlBlendMode::kSrc));
  builder.SaveLayer(std::nullopt, &save_paint);
  builder.Restore();
 
  // Should be solid red as the destructive color filter floods the clip.
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, AdvancedBlendColorFilterWithDestinationOpacity) {
  DisplayListBuilder builder;
 
  builder.DrawPaint(DlPaint(DlColor::kWhite()));
 
  DlPaint save_paint;
  save_paint.setOpacity(0.3);
  save_paint.setColorFilter(DlColorFilter::MakeBlend(DlColor::kTransparent(),
                                                     DlBlendMode::kSaturation));
  builder.SaveLayer(std::nullopt, &save_paint);
  builder.DrawRect(DlRect::MakeXYWH(100, 100, 300, 300),
                   DlPaint(DlColor::kMaroon()));
  builder.DrawRect(DlRect::MakeXYWH(200, 200, 300, 300),
                   DlPaint(DlColor::kBlue()));
  builder.Restore();
 
  // Should be solid red as the destructive color filter floods the clip.
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
TEST_P(AiksTest, EmulatedAdvancedBlendRestore) {
  DisplayListBuilder builder;
 
  builder.DrawPaint(DlPaint(DlColor::kWhite()));
  builder.Save();
  builder.ClipRect(DlRect::MakeLTRB(100, 100, 400, 300));
 
  // Draw should apply the clip, even though it is an advanced blend.
  builder.DrawRect(DlRect::MakeLTRB(0, 0, 400, 300),
                   DlPaint()
                       .setColor(DlColor::kRed())
                       .setBlendMode(DlBlendMode::kDifference));
  // This color should not show if clip is still functional.
  builder.DrawRect(DlRect::MakeLTRB(0, 0, 100, 100),
                   DlPaint().setColor(DlColor::kBlue()));
  builder.Restore();
 
  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
}
 
}  // namespace testing
}  // namespace impeller