Separate save layer calls into a canvas pass.

Author: chinmaygarde

impeller/aiks/BUILD.gn

@@ -8,6 +8,8 @@ impeller_component("aiks") {
   sources = [
     "canvas.cc",
     "canvas.h",
+    "canvas_pass.cc",
+    "canvas_pass.h",
     "image.cc",
     "image.h",
     "paint.cc",

impeller/aiks/canvas.cc

@@ -12,18 +12,14 @@ namespace impeller {
 
 Canvas::Canvas() {
   xformation_stack_.push({});
-
-  Paint default_paint;
-  default_paint.color = Color::White();
-  paint_stack_.push(default_paint);
+  passes_.emplace_back(CanvasPass{});
 }
 
 Canvas::~Canvas() = default;
 
 void Canvas::Save() {
   FML_DCHECK(xformation_stack_.size() > 0);
   xformation_stack_.push(xformation_stack_.top());
-  paint_stack_.push(paint_stack_.top());
 }
 
 bool Canvas::Restore() {
@@ -32,7 +28,6 @@ bool Canvas::Restore() {
     return false;
   }
   xformation_stack_.pop();
-  paint_stack_.pop();
   return true;
 }
 
@@ -69,46 +64,49 @@ void Canvas::RestoreToCount(size_t count) {
 }
 
 void Canvas::DrawPath(Path path, Paint paint) {
-  Color color = paint.color;
-  color.alpha *= paint_stack_.top().color.alpha;
-
   Entity entity;
   entity.SetTransformation(GetCurrentTransformation());
   entity.SetPath(std::move(path));
-  entity.SetBackgroundColor(color);
-  entity.SetContents(std::move(paint.contents));
-
-  ops_.emplace_back(std::move(entity));
+  entity.SetContents(paint.CreateContentsForEntity());
+  GetCurrentPass().PushEntity(std::move(entity));
 }
 
 void Canvas::SaveLayer(const Paint& paint, std::optional<Rect> bounds) {
   Save();
-  paint_stack_.top() = paint;
 }
 
 void Canvas::ClipPath(Path path) {
   Entity entity;
   entity.SetTransformation(GetCurrentTransformation());
   entity.SetPath(std::move(path));
   entity.SetIsClip(true);
-  ops_.emplace_back(std::move(entity));
+  GetCurrentPass().PushEntity(std::move(entity));
 }
 
 void Canvas::DrawShadow(Path path, Color color, Scalar elevation) {}
 
 void Canvas::DrawPicture(const Picture& picture) {
-  for (const auto& entity : picture.entities) {
-    auto new_entity = entity;
-    new_entity.SetTransformation(GetCurrentTransformation() *
-                                 new_entity.GetTransformation());
-    ops_.emplace_back(std::move(new_entity));
+  for (const auto& pass : picture.passes) {
+    CanvasPass new_pass;
+    for (const auto& entity : pass.GetPassEntities()) {
+      auto new_entity = entity;
+      new_entity.SetTransformation(GetCurrentTransformation() *
+                                   entity.GetTransformation());
+      new_pass.PushEntity(std::move(new_entity));
+    }
+    passes_.emplace_back(std::move(new_pass));
   }
 }
 
 Picture Canvas::EndRecordingAsPicture() {
   Picture picture;
-  picture.entities = std::move(ops_);
+  picture.passes = std::move(passes_);
   return picture;
 }
 
+CanvasPass& Canvas::GetCurrentPass() {
+  FML_DCHECK(!passes_.empty());
+  return passes_.back();
+}
+
 }  // namespace impeller

impeller/aiks/canvas.h

@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "flutter/fml/macros.h"
+#include "impeller/aiks/canvas_pass.h"
 #include "impeller/aiks/paint.h"
 #include "impeller/aiks/picture.h"
 #include "impeller/geometry/matrix.h"
@@ -58,8 +59,9 @@ class Canvas {
 
  private:
   std::stack<Matrix> xformation_stack_;
-  std::stack<Paint> paint_stack_;
-  std::vector<Entity> ops_;
+  std::vector<CanvasPass> passes_;
+
+  CanvasPass& GetCurrentPass();
 
   FML_DISALLOW_COPY_AND_ASSIGN(Canvas);
 };

impeller/aiks/canvas_pass.cc

@@ -0,0 +1,21 @@
+// 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/aiks/canvas_pass.h"
+
+namespace impeller {
+
+CanvasPass::CanvasPass() = default;
+
+CanvasPass::~CanvasPass() = default;
+
+void CanvasPass::PushEntity(Entity entity) {
+  ops_.emplace_back(std::move(entity));
+}
+
+const std::vector<Entity>& CanvasPass::GetPassEntities() const {
+  return ops_;
+}
+
+}  // namespace impeller

impeller/aiks/canvas_pass.h

@@ -0,0 +1,28 @@
+// 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 <vector>
+
+#include "flutter/fml/macros.h"
+#include "impeller/entity/entity.h"
+
+namespace impeller {
+
+class CanvasPass {
+ public:
+  CanvasPass();
+
+  ~CanvasPass();
+
+  void PushEntity(Entity entity);
+
+  const std::vector<Entity>& GetPassEntities() const;
+
+ private:
+  std::vector<Entity> ops_;
+};
+
+}  // namespace impeller

impeller/aiks/paint.cc

@@ -6,6 +6,14 @@
 
 namespace impeller {
 
-//
+std::shared_ptr<Contents> Paint::CreateContentsForEntity() const {
+  if (!color.IsTransparent()) {
+    auto solid_color = std::make_shared<SolidColorContents>();
+    solid_color->SetColor(color);
+    return solid_color;
+  }
+
+  return nullptr;
+}
 
 }  // namespace impeller

impeller/aiks/paint.h

@@ -14,7 +14,8 @@ namespace impeller {
 struct Paint {
   Color color;
   Scalar stroke_width = 0.0;
-  std::shared_ptr<Contents> contents;
+
+  std::shared_ptr<Contents> CreateContentsForEntity() const;
 };
 
 }  // namespace impeller

impeller/aiks/picture.h

@@ -8,12 +8,13 @@
 #include <vector>
 
 #include "flutter/fml/macros.h"
+#include "impeller/aiks/canvas_pass.h"
 #include "impeller/entity/entity.h"
 
 namespace impeller {
 
 struct Picture {
-  std::vector<Entity> entities;
+  std::vector<CanvasPass> passes;
 };
 
 }  // namespace impeller

impeller/aiks/picture_renderer.cc

@@ -29,10 +29,14 @@ bool PictureRenderer::Render(const Surface& surface,
     return false;
   }
 
-  return entity_renderer_.RenderEntities(surface,          //
-                                         onscreen_pass,    //
-                                         picture.entities  //
-  );
+  for (const auto& pass : picture.passes) {
+    if (!entity_renderer_.RenderEntities(surface, onscreen_pass,
+                                         pass.GetPassEntities())) {
+      return false;
+    }
+  }
+
+  return true;
 }
 
 }  // namespace impeller

impeller/entity/contents.cc

@@ -95,6 +95,10 @@ bool LinearGradientContents::Render(const ContentRenderer& renderer,
  ******* SolidColorContents
  ******************************************************************************/
 
+SolidColorContents::SolidColorContents() = default;
+
+SolidColorContents::~SolidColorContents() = default;
+
 void SolidColorContents::SetColor(Color color) {
   color_ = color;
 }
@@ -135,7 +139,7 @@ bool SolidColorContents::Render(const ContentRenderer& renderer,
   VS::FrameInfo frame_info;
   frame_info.mvp =
       Matrix::MakeOrthographic(surface.GetSize()) * entity.GetTransformation();
-  frame_info.color = entity.GetBackgroundColor();
+  frame_info.color = color_;
   VS::BindFrameInfo(cmd, pass.GetTransientsBuffer().EmplaceUniform(frame_info));
 
   cmd.primitive_type = PrimitiveType::kTriangle;