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// Copyright 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CCSchedulerStateMachine_h
#define CCSchedulerStateMachine_h
#include <string>
#include "base/basictypes.h"
namespace cc {
// The SchedulerStateMachine decides how to coordinate main thread activites
// like painting/running javascript with rendering and input activities on the
// impl thread.
//
// The state machine tracks internal state but is also influenced by external state.
// Internal state includes things like whether a frame has been requested, while
// external state includes things like the current time being near to the vblank time.
//
// The scheduler seperates "what to do next" from the updating of its internal state to
// make testing cleaner.
class SchedulerStateMachine {
public:
SchedulerStateMachine();
enum CommitState {
COMMIT_STATE_IDLE,
COMMIT_STATE_FRAME_IN_PROGRESS,
COMMIT_STATE_READY_TO_COMMIT,
COMMIT_STATE_WAITING_FOR_FIRST_DRAW,
};
enum TextureState {
LAYER_TEXTURE_STATE_UNLOCKED,
LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD,
LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD,
};
enum ContextState {
CONTEXT_ACTIVE,
CONTEXT_LOST,
CONTEXT_RECREATING,
};
bool commitPending() const
{
return m_commitState != COMMIT_STATE_IDLE;
}
bool redrawPending() const { return m_needsRedraw; }
enum Action {
ACTION_NONE,
ACTION_BEGIN_FRAME,
ACTION_COMMIT,
ACTION_DRAW_IF_POSSIBLE,
ACTION_DRAW_FORCED,
ACTION_BEGIN_CONTEXT_RECREATION,
ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD,
};
Action nextAction() const;
void updateState(Action);
// Indicates whether the scheduler needs a vsync callback in order to make
// progress.
bool vsyncCallbackNeeded() const;
// Indicates that the system has entered and left a vsync callback.
// The scheduler will not draw more than once in a given vsync callback.
void didEnterVSync();
void didLeaveVSync();
// Indicates whether the LayerTreeHostImpl is visible.
void setVisible(bool);
// Indicates that a redraw is required, either due to the impl tree changing
// or the screen being damaged and simply needing redisplay.
void setNeedsRedraw();
// As setNeedsRedraw(), but ensures the draw will definitely happen even if
// we are not visible.
void setNeedsForcedRedraw();
// Indicates whether ACTION_DRAW_IF_POSSIBLE drew to the screen or not.
void didDrawIfPossibleCompleted(bool success);
// Indicates that a new commit flow needs to be performed, either to pull
// updates from the main thread to the impl, or to push deltas from the impl
// thread to main.
void setNeedsCommit();
// As setNeedsCommit(), but ensures the beginFrame will definitely happen even if
// we are not visible.
void setNeedsForcedCommit();
// Call this only in response to receiving an ACTION_BEGIN_FRAME
// from nextState. Indicates that all painting is complete.
void beginFrameComplete();
// Call this only in response to receiving an ACTION_BEGIN_FRAME
// from nextState if the client rejects the beginFrame message.
void beginFrameAborted();
// Request exclusive access to the textures that back single buffered
// layers on behalf of the main thread. Upon acqusition,
// ACTION_DRAW_IF_POSSIBLE will not draw until the main thread releases the
// textures to the impl thread by committing the layers.
void setMainThreadNeedsLayerTextures();
// Indicates whether we can successfully begin a frame at this time.
void setCanBeginFrame(bool can) { m_canBeginFrame = can; }
// Indicates whether drawing would, at this time, make sense.
// canDraw can be used to supress flashes or checkerboarding
// when such behavior would be undesirable.
void setCanDraw(bool can) { m_canDraw = can; }
void didLoseContext();
void didRecreateContext();
// Exposed for testing purposes.
void setMaximumNumberOfFailedDrawsBeforeDrawIsForced(int);
std::string toString();
protected:
bool shouldDrawForced() const;
bool drawSuspendedUntilCommit() const;
bool scheduledToDraw() const;
bool shouldDraw() const;
bool shouldAcquireLayerTexturesForMainThread() const;
bool hasDrawnThisFrame() const;
CommitState m_commitState;
int m_currentFrameNumber;
int m_lastFrameNumberWhereDrawWasCalled;
int m_consecutiveFailedDraws;
int m_maximumNumberOfFailedDrawsBeforeDrawIsForced;
bool m_needsRedraw;
bool m_needsForcedRedraw;
bool m_needsForcedRedrawAfterNextCommit;
bool m_needsCommit;
bool m_needsForcedCommit;
bool m_mainThreadNeedsLayerTextures;
bool m_insideVSync;
bool m_visible;
bool m_canBeginFrame;
bool m_canDraw;
bool m_drawIfPossibleFailed;
TextureState m_textureState;
ContextState m_contextState;
DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
};
}
#endif // CCSchedulerStateMachine_h
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