flutter::VolatilePathTracker Class Reference

#include <volatile_path_tracker.h>

Classes
struct	TrackedPath
	The fields of this struct must only accessed on the UI task runner. More...

Public Member Functions
	VolatilePathTracker (fml::RefPtr< fml::TaskRunner > ui_task_runner, bool enabled)
void	Track (const std::shared_ptr< TrackedPath > &path)
void	OnFrame ()
bool	enabled () const

Static Public Attributes
static constexpr int	kFramesOfVolatility = 2

Friends
class	testing::ShellTest

Detailed Description

A cache for paths drawn from dart:ui.

Whenever a flutter::CanvasPath is created, it must Insert an entry into this cache. Whenever a frame is drawn, the shell must call OnFrame. The cache will flip the volatility bit on the SkPath and remove it from the cache. If the Dart object is released, Erase must be called to avoid tracking a path that is no longer referenced in Dart code.

Enabling this cache may cause difficult to predict minor pixel differences when paths are rendered. If deterministic rendering is needed, e.g. for a screen diffing test, this class will not cache any paths and will automatically set the volatility of the path to false.

Definition at line 36 of file volatile_path_tracker.h.

Constructor & Destructor Documentation

VolatilePathTracker()

flutter::VolatilePathTracker::VolatilePathTracker	(	fml::RefPtr< fml::TaskRunner >	ui_task_runner,
		bool	enabled
	)

Definition at line 11 of file volatile_path_tracker.cc.

    : ui_task_runner_(std::move(ui_task_runner)), enabled_(enabled) {}

Member Function Documentation

enabled()

bool flutter::VolatilePathTracker::enabled ( ) const

inline

Definition at line 65 of file volatile_path_tracker.h.

{ return enabled_; }

OnFrame()

void flutter::VolatilePathTracker::OnFrame

(

)

Definition at line 27 of file volatile_path_tracker.cc.

                                  {
  FML_DCHECK(ui_task_runner_->RunsTasksOnCurrentThread());
  if (!enabled_) {
    return;
  }
 
  paths_.erase(std::remove_if(paths_.begin(), paths_.end(),
                              [](const std::weak_ptr<TrackedPath>& weak_path) {
                                auto path = weak_path.lock();
                                if (!path) {
                                  return true;
                                }
                                path->frame_count++;
                                if (path->frame_count >= kFramesOfVolatility) {
                                  path->path.setIsVolatile(false);
                                  path->tracking_volatility = false;
                                  return true;
                                }
                                return false;
                              }),
               paths_.end());
}

Track()

void flutter::VolatilePathTracker::Track

(

const std::shared_ptr< TrackedPath > &

path

)

Definition at line 16 of file volatile_path_tracker.cc.

                                                                      {
  FML_DCHECK(ui_task_runner_->RunsTasksOnCurrentThread());
  FML_DCHECK(path);
  FML_DCHECK(path->path.isVolatile());
  if (!enabled_) {
    path->path.setIsVolatile(false);
    return;
  }
  paths_.push_back(path);
}

Friends And Related Symbol Documentation

testing::ShellTest

friend class testing::ShellTest

friend

Definition at line 72 of file volatile_path_tracker.h.

Member Data Documentation

kFramesOfVolatility

constexpr int flutter::VolatilePathTracker::kFramesOfVolatility = 2

staticconstexpr

Definition at line 48 of file volatile_path_tracker.h.

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The documentation for this class was generated from the following files:

• lib/ui/volatile_path_tracker.h
• lib/ui/volatile_path_tracker.cc