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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 <vector>
#include "flutter/flow/surface_frame.h"
#include "flutter/fml/memory/ref_counted.h"
#include "flutter/fml/raster_thread_merger.h"
#include "third_party/skia/include/core/SkCanvas.h"
#include "third_party/skia/include/core/SkPath.h"
#include "third_party/skia/include/core/SkPoint.h"
#include "third_party/skia/include/core/SkRRect.h"
#include "third_party/skia/include/core/SkRect.h"
#include "third_party/skia/include/core/SkSize.h"
#include "third_party/skia/include/core/SkSurface.h"
namespace flutter {
// TODO(chinmaygarde): Make these enum names match the style guide.
enum MutatorType { clip_rect, clip_rrect, clip_path, transform, opacity };
// Stores mutation information like clipping or transform.
// The `type` indicates the type of the mutation: clip_rect, transform and etc.
// Each `type` is paired with an object that supports the mutation. For example,
// if the `type` is clip_rect, `rect()` is used the represent the rect to be
// clipped. One mutation object must only contain one type of mutation.
class Mutator {
Mutator(const Mutator& other) {
type_ = other.type_;
switch (other.type_) {
case clip_rect:
rect_ = other.rect_;
case clip_rrect:
rrect_ = other.rrect_;
case clip_path:
path_ = new SkPath(*other.path_);
case transform:
matrix_ = other.matrix_;
case opacity:
alpha_ = other.alpha_;
explicit Mutator(const SkRect& rect) : type_(clip_rect), rect_(rect) {}
explicit Mutator(const SkRRect& rrect) : type_(clip_rrect), rrect_(rrect) {}
explicit Mutator(const SkPath& path)
: type_(clip_path), path_(new SkPath(path)) {}
explicit Mutator(const SkMatrix& matrix)
: type_(transform), matrix_(matrix) {}
explicit Mutator(const int& alpha) : type_(opacity), alpha_(alpha) {}
const MutatorType& GetType() const { return type_; }
const SkRect& GetRect() const { return rect_; }
const SkRRect& GetRRect() const { return rrect_; }
const SkPath& GetPath() const { return *path_; }
const SkMatrix& GetMatrix() const { return matrix_; }
const int& GetAlpha() const { return alpha_; }
float GetAlphaFloat() const { return (alpha_ / 255.0); }
bool operator==(const Mutator& other) const {
if (type_ != other.type_) {
return false;
switch (type_) {
case clip_rect:
return rect_ == other.rect_;
case clip_rrect:
return rrect_ == other.rrect_;
case clip_path:
return *path_ == *other.path_;
case transform:
return matrix_ == other.matrix_;
case opacity:
return alpha_ == other.alpha_;
return false;
bool operator!=(const Mutator& other) const { return !operator==(other); }
bool IsClipType() {
return type_ == clip_rect || type_ == clip_rrect || type_ == clip_path;
~Mutator() {
if (type_ == clip_path) {
delete path_;
MutatorType type_;
union {
SkRect rect_;
SkRRect rrect_;
SkMatrix matrix_;
SkPath* path_;
int alpha_;
}; // Mutator
// A stack of mutators that can be applied to an embedded platform view.
// The stack may include mutators like transforms and clips, each mutator
// applies to all the mutators that are below it in the stack and to the
// embedded view.
// For example consider the following stack: [T1, T2, T3], where T1 is the top
// of the stack and T3 is the bottom of the stack. Applying this mutators stack
// to a platform view P1 will result in T1(T2(T3(P1))).
class MutatorsStack {
MutatorsStack() = default;
void PushClipRect(const SkRect& rect);
void PushClipRRect(const SkRRect& rrect);
void PushClipPath(const SkPath& path);
void PushTransform(const SkMatrix& matrix);
void PushOpacity(const int& alpha);
// Removes the `Mutator` on the top of the stack
// and destroys it.
void Pop();
// Returns a reverse iterator pointing to the top of the stack, which is the
// mutator that is furtherest from the leaf node.
const std::vector<std::shared_ptr<Mutator>>::const_reverse_iterator Top()
// Returns a reverse iterator pointing to the bottom of the stack, which is
// the mutator that is closeset from the leaf node.
const std::vector<std::shared_ptr<Mutator>>::const_reverse_iterator Bottom()
// Returns an iterator pointing to the beginning of the mutator vector, which
// is the mutator that is furtherest from the leaf node.
const std::vector<std::shared_ptr<Mutator>>::const_iterator Begin() const;
// Returns an iterator pointing to the end of the mutator vector, which is the
// mutator that is closest from the leaf node.
const std::vector<std::shared_ptr<Mutator>>::const_iterator End() const;
bool is_empty() const { return vector_.empty(); }
bool operator==(const MutatorsStack& other) const {
if (vector_.size() != other.vector_.size()) {
return false;
for (size_t i = 0; i < vector_.size(); i++) {
if (*vector_[i] != *other.vector_[i]) {
return false;
return true;
bool operator==(const std::vector<Mutator>& other) const {
if (vector_.size() != other.size()) {
return false;
for (size_t i = 0; i < vector_.size(); i++) {
if (*vector_[i] != other[i]) {
return false;
return true;
bool operator!=(const MutatorsStack& other) const {
return !operator==(other);
bool operator!=(const std::vector<Mutator>& other) const {
return !operator==(other);
std::vector<std::shared_ptr<Mutator>> vector_;
}; // MutatorsStack
class EmbeddedViewParams {
EmbeddedViewParams() = default;
EmbeddedViewParams(SkMatrix matrix,
SkSize size_points,
MutatorsStack mutators_stack)
: matrix_(matrix),
mutators_stack_(mutators_stack) {
SkPath path;
SkRect starting_rect = SkRect::MakeSize(size_points);
final_bounding_rect_ = path.getBounds();
EmbeddedViewParams(const EmbeddedViewParams& other) {
size_points_ = other.size_points_;
mutators_stack_ = other.mutators_stack_;
matrix_ = other.matrix_;
final_bounding_rect_ = other.final_bounding_rect_;
// The transformation Matrix corresponding to the sum of all the
// transformations in the platform view's mutator stack.
const SkMatrix& transformMatrix() const { return matrix_; };
// The original size of the platform view before any mutation matrix is
// applied.
const SkSize& sizePoints() const { return size_points_; };
// The mutators stack contains the detailed step by step mutations for this
// platform view.
const MutatorsStack& mutatorsStack() const { return mutators_stack_; };
// The bounding rect of the platform view after applying all the mutations.
// Clippings are ignored.
const SkRect& finalBoundingRect() const { return final_bounding_rect_; }
bool operator==(const EmbeddedViewParams& other) const {
return size_points_ == other.size_points_ &&
mutators_stack_ == other.mutators_stack_ &&
final_bounding_rect_ == other.final_bounding_rect_ &&
matrix_ == other.matrix_;
SkMatrix matrix_;
SkSize size_points_;
MutatorsStack mutators_stack_;
SkRect final_bounding_rect_;
enum class PostPrerollResult {
// Frame has successfully rasterized.
// Frame is submitted twice. This is currently only used when
// thread configuration change occurs.
// Frame is dropped and a new frame with the same layer tree is
// attempted. This is currently only used when thread configuration
// change occurs.
// Facilitates embedding of platform views within the flow layer tree.
// Used on iOS, Android (hybrid composite mode), and on embedded platforms
// that provide a system compositor as part of the project arguments.
class ExternalViewEmbedder {
// TODO(cyanglaz): Make embedder own the `EmbeddedViewParams`.
ExternalViewEmbedder() = default;
virtual ~ExternalViewEmbedder() = default;
// Usually, the root canvas is not owned by the view embedder. However, if
// the view embedder wants to provide a canvas to the rasterizer, it may
// return one here. This canvas takes priority over the canvas materialized
// from the on-screen render target.
virtual SkCanvas* GetRootCanvas() = 0;
// Call this in-lieu of |SubmitFrame| to clear pre-roll state and
// sets the stage for the next pre-roll.
virtual void CancelFrame() = 0;
// Indicates the beginning of a frame.
// The `raster_thread_merger` will be null if |SupportsDynamicThreadMerging|
// returns false.
virtual void BeginFrame(
SkISize frame_size,
GrDirectContext* context,
double device_pixel_ratio,
fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) = 0;
virtual void PrerollCompositeEmbeddedView(
int view_id,
std::unique_ptr<EmbeddedViewParams> params) = 0;
// This needs to get called after |Preroll| finishes on the layer tree.
// Returns kResubmitFrame if the frame needs to be processed again, this is
// after it does any requisite tasks needed to bring itself to a valid state.
// Returns kSuccess if the view embedder is already in a valid state.
virtual PostPrerollResult PostPrerollAction(
fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
return PostPrerollResult::kSuccess;
virtual std::vector<SkCanvas*> GetCurrentCanvases() = 0;
// Must be called on the UI thread.
virtual SkCanvas* CompositeEmbeddedView(int view_id) = 0;
// Implementers must submit the frame by calling frame.Submit().
// This method can mutate the root Skia canvas before submitting the frame.
// It can also allocate frames for overlay surfaces to compose hybrid views.
virtual void SubmitFrame(GrDirectContext* context,
std::unique_ptr<SurfaceFrame> frame);
// This method provides the embedder a way to do additional tasks after
// |SubmitFrame|. For example, merge task runners if `should_resubmit_frame`
// is true.
// For example on the iOS embedder, threads are merged in this call.
// A new frame on the platform thread starts immediately. If the GPU thread
// still has some task running, there could be two frames being rendered
// concurrently, which causes undefined behaviors.
// The `raster_thread_merger` will be null if |SupportsDynamicThreadMerging|
// returns false.
virtual void EndFrame(
bool should_resubmit_frame,
fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {}
// Whether the embedder should support dynamic thread merging.
// Returning `true` results a |RasterThreadMerger| instance to be created.
// * See also |BegineFrame| and |EndFrame| for getting the
// |RasterThreadMerger| instance.
virtual bool SupportsDynamicThreadMerging();
// Called when the rasterizer is being torn down.
// This method provides a way to release resources associated with the current
// embedder.
virtual void Teardown();
}; // ExternalViewEmbedder
} // namespace flutter