Add ClearContents to apply specified contents to the entire render target. (flutter#88)

Author: chinmaygarde

impeller/aiks/aiks_unittests.cc

@@ -390,5 +390,13 @@ TEST_F(AiksTest, CanRenderEmojiTextFrame) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+TEST_F(AiksTest, CanDrawPaint) {
+  Paint paint;
+  paint.color = Color::MediumTurquoise();
+  Canvas canvas;
+  canvas.DrawPaint(paint);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 }  // namespace testing
 }  // namespace impeller

impeller/aiks/canvas.cc

@@ -8,6 +8,7 @@
 
 #include "flutter/fml/logging.h"
 #include "impeller/aiks/paint_pass_delegate.h"
+#include "impeller/entity/contents/clear_contents.h"
 #include "impeller/entity/contents/clip_contents.h"
 #include "impeller/entity/contents/text_contents.h"
 #include "impeller/entity/contents/texture_contents.h"
@@ -113,6 +114,16 @@ void Canvas::DrawPath(Path path, Paint paint) {
   GetCurrentPass().AddEntity(std::move(entity));
 }
 
+void Canvas::DrawPaint(Paint paint) {
+  Entity entity;
+  entity.SetTransformation(GetCurrentTransformation());
+  entity.SetStencilDepth(GetStencilDepth());
+  entity.SetContents(
+      std::make_shared<ClearContents>(paint.CreateContentsForEntity()));
+
+  GetCurrentPass().AddEntity(std::move(entity));
+}
+
 void Canvas::DrawRect(Rect rect, Paint paint) {
   DrawPath(PathBuilder{}.AddRect(rect).TakePath(), std::move(paint));
 }

impeller/aiks/canvas.h

@@ -59,6 +59,8 @@ class Canvas {
 
   void DrawPath(Path path, Paint paint);
 
+  void DrawPaint(Paint paint);
+
   void DrawRect(Rect rect, Paint paint);
 
   void DrawCircle(Point center, Scalar radius, Paint paint);

impeller/display_list/display_list_dispatcher.cc

@@ -397,12 +397,15 @@ void DisplayListDispatcher::clipPath(const SkPath& path,
 
 // |flutter::Dispatcher|
 void DisplayListDispatcher::drawColor(SkColor color, SkBlendMode mode) {
-  UNIMPLEMENTED;
+  Paint paint;
+  paint.color = ToColor(color);
+  FML_LOG(ERROR) << "Blend mode on drawColor ignored.";
+  canvas_.DrawPaint(paint);
 }
 
 // |flutter::Dispatcher|
 void DisplayListDispatcher::drawPaint() {
-  UNIMPLEMENTED;
+  canvas_.DrawPaint(paint_);
 }
 
 // |flutter::Dispatcher|

impeller/entity/BUILD.gn

@@ -29,6 +29,8 @@ impeller_shaders("entity_shaders") {
 
 impeller_component("entity") {
   sources = [
+    "contents/clear_contents.cc",
+    "contents/clear_contents.h",
     "contents/clip_contents.cc",
     "contents/clip_contents.h",
     "contents/content_context.cc",

impeller/entity/contents/clear_contents.cc

@@ -0,0 +1,34 @@
+// 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/clear_contents.h"
+
+#include "impeller/entity/entity.h"
+#include "impeller/geometry/path_builder.h"
+#include "impeller/renderer/render_pass.h"
+
+namespace impeller {
+
+ClearContents::ClearContents(std::shared_ptr<Contents> contents)
+    : contents_(std::move(contents)) {}
+
+ClearContents::~ClearContents() = default;
+
+// |Contents|
+bool ClearContents::Render(const ContentContext& renderer,
+                           const Entity& entity,
+                           RenderPass& pass) const {
+  if (contents_ == nullptr) {
+    return false;
+  }
+  // Instead of an entity that doesn't know its size because the render target
+  // size was unknown to it at construction time, create a copy but substitute
+  // the contents with the replacements.
+  Entity clear_entity = entity;
+  clear_entity.SetPath(
+      PathBuilder{}.AddRect(Size(pass.GetRenderTargetSize())).TakePath());
+  return contents_->Render(renderer, clear_entity, pass);
+}
+
+}  // namespace impeller

impeller/entity/contents/clear_contents.h

@@ -0,0 +1,33 @@
+// 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 "flutter/fml/macros.h"
+#include "impeller/entity/contents/contents.h"
+
+namespace impeller {
+
+//------------------------------------------------------------------------------
+/// @brief      Disregard existing contents on the render target and use the
+///             provided filter to render to the entire target.
+///
+class ClearContents final : public Contents {
+ public:
+  ClearContents(std::shared_ptr<Contents> contents);
+
+  ~ClearContents();
+
+  // |Contents|
+  bool Render(const ContentContext& renderer,
+              const Entity& entity,
+              RenderPass& pass) const override;
+
+ private:
+  std::shared_ptr<Contents> contents_;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(ClearContents);
+};
+
+}  // namespace impeller