[Impeller] support for foreground shaders on text

ci/licenses_golden/licenses_flutter

@@ -1126,6 +1126,8 @@ ORIGIN: ../../../flutter/impeller/entity/contents/clip_contents.cc + ../../../fl
 ORIGIN: ../../../flutter/impeller/entity/contents/clip_contents.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/color_source_contents.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/color_source_contents.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/entity/contents/color_source_text_contents.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/impeller/entity/contents/color_source_text_contents.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/content_context.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/content_context.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/entity/contents/contents.cc + ../../../flutter/LICENSE
@@ -3661,6 +3663,8 @@ FILE: ../../../flutter/impeller/entity/contents/clip_contents.cc
 FILE: ../../../flutter/impeller/entity/contents/clip_contents.h
 FILE: ../../../flutter/impeller/entity/contents/color_source_contents.cc
 FILE: ../../../flutter/impeller/entity/contents/color_source_contents.h
+FILE: ../../../flutter/impeller/entity/contents/color_source_text_contents.cc
+FILE: ../../../flutter/impeller/entity/contents/color_source_text_contents.h
 FILE: ../../../flutter/impeller/entity/contents/content_context.cc
 FILE: ../../../flutter/impeller/entity/contents/content_context.h
 FILE: ../../../flutter/impeller/entity/contents/contents.cc

impeller/aiks/canvas.cc

@@ -12,6 +12,7 @@
 #include "impeller/aiks/paint_pass_delegate.h"
 #include "impeller/entity/contents/atlas_contents.h"
 #include "impeller/entity/contents/clip_contents.h"
+#include "impeller/entity/contents/color_source_text_contents.h"
 #include "impeller/entity/contents/rrect_shadow_contents.h"
 #include "impeller/entity/contents/text_contents.h"
 #include "impeller/entity/contents/texture_contents.h"
@@ -380,16 +381,40 @@ void Canvas::DrawTextFrame(const TextFrame& text_frame,
                            const Paint& paint) {
   lazy_glyph_atlas_->AddTextFrame(text_frame);
 
+  Entity entity;
+  entity.SetStencilDepth(GetStencilDepth());
+  entity.SetBlendMode(paint.blend_mode);
+
   auto text_contents = std::make_shared<TextContents>();
   text_contents->SetTextFrame(text_frame);
   text_contents->SetGlyphAtlas(lazy_glyph_atlas_);
+
+  if (paint.color_source.has_value()) {
+    auto& source = paint.color_source.value();
+    auto color_text_contents = std::make_shared<ColorSourceTextContents>();
+    entity.SetTransformation(GetCurrentTransformation());
+
+    Entity test;
+    auto cvg = text_contents->GetCoverage(test).value();
+    color_text_contents->SetTextPosition(cvg.origin + position);
+
+    text_contents->SetInverseMatrix(
+        Matrix::MakeTranslation(Vector3(-cvg.origin.x, -cvg.origin.y, 0)));
+    color_text_contents->SetTextContents(std::move(text_contents));
+    color_text_contents->SetColorSourceContents(source());
+
+    entity.SetContents(
+        paint.WithFilters(std::move(color_text_contents), false));
+
+    GetCurrentPass().AddEntity(entity);
+    return;
+  }
+
   text_contents->SetColor(paint.color);
 
-  Entity entity;
   entity.SetTransformation(GetCurrentTransformation() *
                            Matrix::MakeTranslation(position));
-  entity.SetStencilDepth(GetStencilDepth());
-  entity.SetBlendMode(paint.blend_mode);
+
   entity.SetContents(paint.WithFilters(std::move(text_contents), true));
 
   GetCurrentPass().AddEntity(entity);

impeller/display_list/display_list_unittests.cc

@@ -56,6 +56,25 @@ TEST_P(DisplayListTest, CanDrawTextBlob) {
   ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
 }
 
+TEST_P(DisplayListTest, CanDrawTextBlobWithGradient) {
+  flutter::DisplayListBuilder builder;
+
+  std::vector<flutter::DlColor> colors = {flutter::DlColor::kBlue(),
+                                          flutter::DlColor::kRed()};
+  const float stops[2] = {0.0, 1.0};
+
+  auto linear = flutter::DlColorSource::MakeLinear({0.0, 0.0}, {300.0, 300.0},
+                                                   2, colors.data(), stops,
+                                                   flutter::DlTileMode::kClamp);
+  flutter::DlPaint paint;
+  paint.setColorSource(linear);
+
+  builder.DrawTextBlob(
+      SkTextBlob::MakeFromString("Hello World", CreateTestFont()), 100, 100,
+      paint);
+  ASSERT_TRUE(OpenPlaygroundHere(builder.Build()));
+}
+
 TEST_P(DisplayListTest, CanDrawTextWithSaveLayer) {
   flutter::DisplayListBuilder builder;
   builder.DrawTextBlob(SkTextBlob::MakeFromString("Hello", CreateTestFont()),

impeller/entity/BUILD.gn

@@ -121,6 +121,8 @@ impeller_component("entity") {
     "contents/clip_contents.h",
     "contents/color_source_contents.cc",
     "contents/color_source_contents.h",
+    "contents/color_source_text_contents.cc",
+    "contents/color_source_text_contents.h",
     "contents/content_context.cc",
     "contents/content_context.h",
     "contents/contents.cc",

impeller/entity/contents/color_source_contents.h

@@ -22,6 +22,8 @@ class ColorSourceContents : public Contents {
 
   void SetEffectTransform(Matrix matrix);
 
+  const Matrix& GetInverseMatrix() const;
+
   void SetAlpha(Scalar alpha);
 
   // |Contents|
@@ -34,8 +36,6 @@ class ColorSourceContents : public Contents {
  protected:
   const std::shared_ptr<Geometry>& GetGeometry() const;
 
-  const Matrix& GetInverseMatrix() const;
-
   Scalar GetAlpha() const;
 
  private:

impeller/entity/contents/color_source_text_contents.cc

@@ -0,0 +1,84 @@
+// 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 "impeller/entity/contents/color_source_text_contents.h"
+
+#include "impeller/entity/contents/content_context.h"
+#include "impeller/entity/contents/texture_contents.h"
+#include "impeller/renderer/render_pass.h"
+
+namespace impeller {
+
+ColorSourceTextContents::ColorSourceTextContents() = default;
+
+ColorSourceTextContents::~ColorSourceTextContents() = default;
+
+void ColorSourceTextContents::SetTextContents(
+    std::shared_ptr<TextContents> text_contents) {
+  text_contents_ = std::move(text_contents);
+}
+
+void ColorSourceTextContents::SetColorSourceContents(
+    std::shared_ptr<ColorSourceContents> color_source_contents) {
+  color_source_contents_ = std::move(color_source_contents);
+}
+
+std::optional<Rect> ColorSourceTextContents::GetCoverage(
+    const Entity& entity) const {
+  return text_contents_->GetCoverage(entity);
+}
+
+void ColorSourceTextContents::SetTextPosition(Point position) {
+  position_ = position;
+}
+
+bool ColorSourceTextContents::Render(const ContentContext& renderer,
+                                     const Entity& entity,
+                                     RenderPass& pass) const {
+  auto coverage = text_contents_->GetCoverage(entity);
+  if (!coverage.has_value()) {
+    return true;
+  }
+  auto transform = entity.GetTransformation();
+
+  text_contents_->SetColor(Color::Black());
+  color_source_contents_->SetGeometry(
+      Geometry::MakeRect(Rect::MakeSize(coverage->size)));
+
+  // offset the color source so it behaves as if it were drawn in the original
+  // position.
+  auto effect_transform =
+      color_source_contents_->GetInverseMatrix().Invert().Translate(-position_);
+  color_source_contents_->SetEffectTransform(effect_transform);
+
+  auto new_texture = renderer.MakeSubpass(
+      "Text Color Blending", ISize::Ceil(coverage.value().size),
+      [&](const ContentContext& context, RenderPass& pass) {
+        Entity sub_entity;
+        sub_entity.SetTransformation(transform);
+        sub_entity.SetContents(text_contents_);
+        sub_entity.SetBlendMode(BlendMode::kSource);
+        if (!sub_entity.Render(context, pass)) {
+          return false;
+        }
+
+        sub_entity.SetContents(color_source_contents_);
+        sub_entity.SetBlendMode(BlendMode::kSourceIn);
+        return sub_entity.Render(context, pass);
+      });
+  if (!new_texture) {
+    return false;
+  }
+
+  auto dest_rect = Rect::MakeSize(new_texture->GetSize())
+                       .TransformBounds(transform.Invert())
+                       .Shift(position_);
+
+  auto texture_contents = TextureContents::MakeRect(dest_rect);
+  texture_contents->SetTexture(new_texture);
+  texture_contents->SetSourceRect(Rect::MakeSize(new_texture->GetSize()));
+  return texture_contents->Render(renderer, entity, pass);
+}
+
+}  // namespace impeller

impeller/entity/contents/color_source_text_contents.h

@@ -0,0 +1,48 @@
+// 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.
+
+#pragma once
+
+#include <functional>
+#include <memory>
+#include <variant>
+#include <vector>
+
+#include "flutter/fml/macros.h"
+#include "impeller/entity/contents/color_source_contents.h"
+#include "impeller/entity/contents/contents.h"
+#include "impeller/entity/contents/text_contents.h"
+
+namespace impeller {
+
+class ColorSourceTextContents final : public Contents {
+ public:
+  ColorSourceTextContents();
+
+  ~ColorSourceTextContents();
+
+  void SetTextContents(std::shared_ptr<TextContents> text_contents);
+
+  void SetColorSourceContents(
+      std::shared_ptr<ColorSourceContents> color_source_contents);
+
+  void SetTextPosition(Point position);
+
+  // |Contents|
+  std::optional<Rect> GetCoverage(const Entity& entity) const override;
+
+  // |Contents|
+  bool Render(const ContentContext& renderer,
+              const Entity& entity,
+              RenderPass& pass) const override;
+
+ private:
+  Point position_;
+  std::shared_ptr<TextContents> text_contents_;
+  std::shared_ptr<ColorSourceContents> color_source_contents_;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(ColorSourceTextContents);
+};
+
+}  // namespace impeller

impeller/entity/contents/text_contents.cc

@@ -50,6 +50,10 @@ void TextContents::SetColor(Color color) {
   color_ = color;
 }
 
+void TextContents::SetInverseMatrix(Matrix matrix) {
+  inverse_matrix_ = matrix;
+}
+
 std::optional<Rect> TextContents::GetCoverage(const Entity& entity) const {
   auto bounds = frame_.GetBounds();
   if (!bounds.has_value()) {
@@ -71,6 +75,7 @@ static bool CommonRender(
     RenderPass& pass,
     const Color& color,
     const TextFrame& frame,
+    const Matrix& inverse_matrix,
     std::shared_ptr<GlyphAtlas>
         atlas,  // NOLINT(performance-unnecessary-value-param)
     Command& cmd) {
@@ -159,8 +164,10 @@ static bool CommonRender(
 
       auto uv_scaler_a = atlas_glyph_pos->size / atlas_size;
       auto uv_scaler_b = (Point::Round(atlas_glyph_pos->origin) / atlas_size);
-      auto translation = Matrix::MakeTranslation(
-          Vector3(offset_glyph_position.x, offset_glyph_position.y, 0));
+      auto translation =
+          Matrix::MakeTranslation(
+              Vector3(offset_glyph_position.x, offset_glyph_position.y, 0)) *
+          inverse_matrix;
 
       for (const auto& point : unit_points) {
         typename VS::PerVertexData vtx;
@@ -209,8 +216,8 @@ bool TextContents::RenderSdf(const ContentContext& renderer,
   cmd.pipeline = renderer.GetGlyphAtlasSdfPipeline(opts);
   cmd.stencil_reference = entity.GetStencilDepth();
 
-  return CommonRender<GlyphAtlasSdfPipeline>(renderer, entity, pass, color_,
-                                             frame_, atlas, cmd);
+  return CommonRender<GlyphAtlasSdfPipeline>(
+      renderer, entity, pass, color_, frame_, inverse_matrix_, atlas, cmd);
 }
 
 bool TextContents::Render(const ContentContext& renderer,
@@ -245,7 +252,7 @@ bool TextContents::Render(const ContentContext& renderer,
   cmd.stencil_reference = entity.GetStencilDepth();
 
   return CommonRender<GlyphAtlasPipeline>(renderer, entity, pass, color_,
-                                          frame_, atlas, cmd);
+                                          frame_, inverse_matrix_, atlas, cmd);
 }
 
 }  // namespace impeller

impeller/entity/contents/text_contents.h

@@ -32,6 +32,8 @@ class TextContents final : public Contents {
 
   void SetColor(Color color);
 
+  void SetInverseMatrix(Matrix matrix);
+
   // |Contents|
   std::optional<Rect> GetCoverage(const Entity& entity) const override;
 
@@ -49,6 +51,7 @@ class TextContents final : public Contents {
   TextFrame frame_;
   Color color_;
   mutable std::shared_ptr<LazyGlyphAtlas> lazy_atlas_;
+  Matrix inverse_matrix_;
 
   std::shared_ptr<GlyphAtlas> ResolveAtlas(
       GlyphAtlas::Type type,

impeller/geometry/geometry_unittests.cc

@@ -1541,6 +1541,13 @@ TEST(GeometryTest, RectGetPoints) {
   ASSERT_POINT_NEAR(points[3], Point(400, 600));
 }
 
+TEST(GeometryTest, RectShift) {
+  auto r = Rect::MakeLTRB(0, 0, 100, 100);
+
+  ASSERT_EQ(r.Shift(Point(10, 5)), Rect::MakeLTRB(10, 5, 110, 105));
+  ASSERT_EQ(r.Shift(Point(-10, -5)), Rect::MakeLTRB(-10, -5, 90, 95));
+}
+
 TEST(GeometryTest, RectGetTransformedPoints) {
   Rect r(100, 200, 300, 400);
   auto points = r.GetTransformedPoints(Matrix::MakeTranslation({10, 20}));

impeller/geometry/rect.h

@@ -238,6 +238,12 @@ struct TRect {
 
     return *this;
   }
+
+  /// @brief  Returns a new rectangle translated by the given offset.
+  constexpr TRect<T> Shift(TPoint<T> offset) const {
+    return TRect(origin.x + offset.x, origin.y + offset.y, size.width,
+                 size.height);
+  }
 };
 
 using Rect = TRect<Scalar>;