skia2/include/utils/SkDeferredCanvas.h

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkDeferredCanvas_DEFINED
#define SkDeferredCanvas_DEFINED

#include "SkCanvas.h"
#include "SkPixelRef.h"

class DeferredDevice;

/** \class SkDeferredCanvas
    Subclass of SkCanvas that encapsulates an SkPicture or SkGPipe for deferred
    drawing. The main difference between this class and SkPictureRecord (the
    canvas provided by SkPicture) is that this is a full drop-in replacement
    for SkCanvas, while SkPictureRecord only supports draw operations.
    SkDeferredCanvas will transparently trigger the flushing of deferred
    draw operations when an attempt is made to access the pixel data.
*/
class SK_API SkDeferredCanvas : public SkCanvas {
public:
    class DeviceContext;

    SkDeferredCanvas();

    /** Construct a canvas with the specified device to draw into.
        Equivalent to calling default constructor, then setDevice.
        @param device Specifies a device for the canvas to draw into.
    */
    explicit SkDeferredCanvas(SkDevice* device);

    /** Construct a canvas with the specified device to draw into, and
     *  a device context. Equivalent to calling default constructor, then
     *  setDevice.
     *  @param device Specifies a device for the canvas to draw into.
     *  @param deviceContext interface for the device's the graphics context
     */
    explicit SkDeferredCanvas(SkDevice* device, DeviceContext* deviceContext);

    virtual ~SkDeferredCanvas();

    /**
     *  Specify a device to be used by this canvas. Calling setDevice will
     *  release the previously set device, if any.
     *
     *  @param device The device that the canvas will raw into
     *  @return The device argument, for convenience.
     */
    virtual SkDevice* setDevice(SkDevice* device);

    /**
     *  Specify a deviceContext to be used by this canvas. Calling
     *  setDeviceContext will release the previously set deviceContext, if any.
     *  A deviceContext must be specified if the device uses a graphics context
     *  that requires some form of state initialization prior to drawing
     *  and/or explicit flushing to synchronize the execution of rendering
     *  operations.
     *  Note: Must be called after the device is set with setDevice.
     *
     *  @deviceContext interface for the device's the graphics context
     *  @return The deviceContext argument, for convenience.
     */
    DeviceContext* setDeviceContext(DeviceContext* deviceContext);

    /**
     *  Enable or disable deferred drawing. When deferral is disabled,
     *  pending draw operations are immediately flushed and from then on,
     *  the SkDeferredCanvas behaves just like a regular SkCanvas.
     *  This method must not be called while the save/restore stack is in use.
     *  @param deferred true/false
     */
    void setDeferredDrawing(bool deferred);

    /**
     *  Returns true if deferred drawing is currenlty enabled.
     */
    bool isDeferredDrawing() const;

    /**
     *  Returns true if the canvas contains a fresh frame.  A frame is 
     *  considered fresh when its content do not depend on the contents
     *  of the previous frame. For example, if a canvas is cleared before
     *  drawing each frame, the frames will all be considered fresh.
     *  A frame is defined as the graphics image produced by as a result
     *  of all the canvas draws operation executed between two successive
     *  calls to isFreshFrame.  The result of isFreshFrame is computed
     *  conservatively, so it may report false negatives.
     */
    bool isFreshFrame() const;

    /**
     *  Specify the maximum number of bytes to be allocated for the purpose
     *  of recording draw commands to this canvas.  The default limit, is
     *  64MB.
     *  @param maxStorage The maximum number of bytes to be allocated.
     */
    void setMaxRecordingStorage(size_t maxStorage);

    /**
     *  Returns the number of bytes currently allocated for the purpose of
     *  recording draw commands.
     */
    size_t storageAllocatedForRecording() const;

    /**
     * Attempt to reduce the storage allocated for recording by evicting
     * cache resources.
     * @param bytesToFree minimum number of bytes that should be attempted to
     *   be freed.
     * @return number of bytes actually freed.
     */
    size_t freeMemoryIfPossible(size_t bytesToFree);

    // Overrides of the SkCanvas interface
    virtual int save(SaveFlags flags) SK_OVERRIDE;
    virtual int saveLayer(const SkRect* bounds, const SkPaint* paint,
                          SaveFlags flags) SK_OVERRIDE;
    virtual void restore() SK_OVERRIDE;
    virtual bool isDrawingToLayer() const SK_OVERRIDE;
    virtual bool translate(SkScalar dx, SkScalar dy) SK_OVERRIDE;
    virtual bool scale(SkScalar sx, SkScalar sy) SK_OVERRIDE;
    virtual bool rotate(SkScalar degrees) SK_OVERRIDE;
    virtual bool skew(SkScalar sx, SkScalar sy) SK_OVERRIDE;
    virtual bool concat(const SkMatrix& matrix) SK_OVERRIDE;
    virtual void setMatrix(const SkMatrix& matrix) SK_OVERRIDE;
    virtual bool clipRect(const SkRect& rect, SkRegion::Op op,
                          bool doAntiAlias) SK_OVERRIDE;
    virtual bool clipPath(const SkPath& path, SkRegion::Op op,
                          bool doAntiAlias) SK_OVERRIDE;
    virtual bool clipRegion(const SkRegion& deviceRgn,
                            SkRegion::Op op) SK_OVERRIDE;
    virtual void clear(SkColor) SK_OVERRIDE;
    virtual void drawPaint(const SkPaint& paint) SK_OVERRIDE;
    virtual void drawPoints(PointMode mode, size_t count, const SkPoint pts[],
                            const SkPaint& paint) SK_OVERRIDE;
    virtual void drawRect(const SkRect& rect, const SkPaint& paint)
                          SK_OVERRIDE;
    virtual void drawPath(const SkPath& path, const SkPaint& paint)
                          SK_OVERRIDE;
    virtual void drawBitmap(const SkBitmap& bitmap, SkScalar left,
                            SkScalar top, const SkPaint* paint)
                            SK_OVERRIDE;
    virtual void drawBitmapRect(const SkBitmap& bitmap, const SkIRect* src,
                                const SkRect& dst, const SkPaint* paint)
                                SK_OVERRIDE;

    virtual void drawBitmapMatrix(const SkBitmap& bitmap, const SkMatrix& m,
                                  const SkPaint* paint) SK_OVERRIDE;
    virtual void drawBitmapNine(const SkBitmap& bitmap, const SkIRect& center,
                                const SkRect& dst, const SkPaint* paint)
                                SK_OVERRIDE;
    virtual void drawSprite(const SkBitmap& bitmap, int left, int top,
                            const SkPaint* paint) SK_OVERRIDE;
    virtual void drawText(const void* text, size_t byteLength, SkScalar x,
                          SkScalar y, const SkPaint& paint) SK_OVERRIDE;
    virtual void drawPosText(const void* text, size_t byteLength,
                             const SkPoint pos[], const SkPaint& paint)
                             SK_OVERRIDE;
    virtual void drawPosTextH(const void* text, size_t byteLength,
                              const SkScalar xpos[], SkScalar constY,
                              const SkPaint& paint) SK_OVERRIDE;
    virtual void drawTextOnPath(const void* text, size_t byteLength,
                                const SkPath& path, const SkMatrix* matrix,
                                const SkPaint& paint) SK_OVERRIDE;
    virtual void drawPicture(SkPicture& picture) SK_OVERRIDE;
    virtual void drawVertices(VertexMode vmode, int vertexCount,
                              const SkPoint vertices[], const SkPoint texs[],
                              const SkColor colors[], SkXfermode* xmode,
                              const uint16_t indices[], int indexCount,
                              const SkPaint& paint) SK_OVERRIDE;
    virtual SkBounder* setBounder(SkBounder* bounder) SK_OVERRIDE;
    virtual SkDrawFilter* setDrawFilter(SkDrawFilter* filter) SK_OVERRIDE;

public:
    class DeviceContext : public SkRefCnt {
    public:
        SK_DECLARE_INST_COUNT(DeviceContext)

        virtual void prepareForDraw() {}
        
    private:
        typedef SkRefCnt INHERITED;
    };

protected:
    virtual SkCanvas* canvasForDrawIter();
    DeferredDevice* getDeferredDevice() const;

private:
    SkCanvas* drawingCanvas() const;
    SkCanvas* immediateCanvas() const;
    bool isFullFrame(const SkRect*, const SkPaint*) const;
    void validate() const;
    void init();
    bool            fDeferredDrawing;

    friend class SkDeferredCanvasTester; // for unit testing
    typedef SkCanvas INHERITED;
};


#endif