skia2/site/user/api/SkPicture_Reference.md

SkPicture Reference

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class SkPicture : public SkRefCnt {

    static sk_sp<SkPicture> MakeFromStream(SkStream* stream,
                                           const SkDeserialProcs* procs = nullptr);
    static sk_sp<SkPicture> MakeFromData(const SkData* data,
                                         const SkDeserialProcs* procs = nullptr);
    static sk_sp<SkPicture> MakeFromData(const void* data, size_t size,
                                         const SkDeserialProcs* procs = nullptr);
    virtual void playback(SkCanvas* canvas, AbortCallback* callback = nullptr) const = 0;
    virtual SkRect cullRect() const = 0;
    uint32_t uniqueID() const;
    sk_sp<SkData> serialize(const SkSerialProcs* procs = nullptr) const;
    void serialize(SkWStream* stream, const SkSerialProcs* procs = nullptr) const;
    static sk_sp<SkPicture> MakePlaceholder(SkRect cull);
    virtual int approximateOpCount() const = 0;
    virtual size_t approximateBytesUsed() const = 0;
};

Picture records drawing commands made to Canvas. The command stream may be played in whole or in part at a later time.

Picture is an abstract class. Picture may be generated by Picture_Recorder or Drawable, or from Picture previously saved to Data or Stream.

Picture may contain any Canvas drawing command, as well as one or more Canvas_Matrix or Canvas_Clip. Picture has a cull Rect, which is used as a bounding box hint. To limit Picture bounds, use Canvas_Clip when recording or drawing Picture.

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    class AbortCallback {
    public:
        AbortCallback() {}
        virtual ~AbortCallback() {}
        virtual bool abort() = 0;
    };

AbortCallback is an abstract class. An implementation of AbortCallback may passed as a parameter to SkPicture::playback, to stop it before all drawing commands have been processed.

If AbortCallback::abort returns true, SkPicture::playback is interrupted.

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AbortCallback()

Has no effect.

Return Value

abstract class cannot be instantiated

See Also

playback

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virtual ~AbortCallback()

Has no effect.

See Also

playback

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virtual bool abort() = 0

Stops SkPicture playback when some condition is met. A subclass of AbortCallback provides an override for abort() that can stop SkPicture::playback.

The part of SkPicture drawn when aborted is undefined. SkPicture instantiations are free to stop drawing at different points during playback.

If the abort happens inside one or more calls to SkCanvas::save(), stack of SkCanvas matrix and SkCanvas clip values is restored to its state before SkPicture::playback was called.

Return Value

true to stop playback

See Also

playback

Example

JustOneDraw allows the black rectangle to draw but stops playback before the white rectangle appears.

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static sk_sp<SkPicture> MakeFromStream(SkStream* stream, const SkDeserialProcs* procs = nullptr)

Recreates SkPicture that was serialized into a stream. Returns constructed SkPicture if successful; otherwise, returns nullptr. Fails if data does not permit constructing valid SkPicture.

procs->fPictureProc permits supplying a custom function to decode SkPicture. If procs->fPictureProc is nullptr, default decoding is used. procs->fPictureCtx may be used to provide user context to procs->fPictureProc; procs->fPictureProc is called with a pointer to data, data byte length, and user context.

Parameters

stream	container for serial data
procs	custom serial data decoders; may be nullptr

Return Value

SkPicture constructed from stream data

Example

See Also

MakeFromData SkPictureRecorder

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static sk_sp<SkPicture> MakeFromData(const SkData* data, const SkDeserialProcs* procs = nullptr)

Recreates SkPicture that was serialized into data. Returns constructed SkPicture if successful; otherwise, returns nullptr. Fails if data does not permit constructing valid SkPicture.

procs->fPictureProc permits supplying a custom function to decode SkPicture. If procs->fPictureProc is nullptr, default decoding is used. procs->fPictureCtx may be used to provide user context to procs->fPictureProc; procs->fPictureProc is called with a pointer to data, data byte length, and user context.

Parameters

data	container for serial data
procs	custom serial data decoders; may be nullptr

Return Value

SkPicture constructed from data

Example

See Also

MakeFromStream SkPictureRecorder

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static sk_sp<SkPicture> MakeFromData(const void* data, size_t size,
                                     const SkDeserialProcs* procs = nullptr)

Parameters

data	pointer to serial data
size	size of data
procs	custom serial data decoders; may be nullptr

Return Value

SkPicture constructed from data

Example

See Also

MakeFromStream SkPictureRecorder

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virtual void playback(SkCanvas* canvas, AbortCallback* callback = nullptr) const = 0

Replays the drawing commands on the specified canvas. In the case that the commands are recorded, each command in the SkPicture is sent separately to canvas.

To add a single command to draw SkPicture to recording canvas, call SkCanvas::drawPicture instead.

Parameters

canvas	receiver of drawing commands
callback	allows interruption of playback

Example

See Also

SkCanvas::drawPicture

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virtual SkRect cullRect() const = 0

Returns cull SkRect for this picture, passed in when SkPicture was created. Returned SkRect does not specify clipping SkRect for SkPicture; cull is hint of SkPicture bounds.

SkPicture is free to discard recorded drawing commands that fall outside cull.

Return Value

bounds passed when SkPicture was created

Example

Picture recorded bounds are smaller than contents; contents outside recorded bounds may be drawn, and are drawn in this example.

See Also

SkCanvas::clipRect

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uint32_t uniqueID()const

Returns a non-zero value unique among SkPicture in Skia process.

Return Value

identifier for SkPicture

Example

Example Output

empty picture id = 1
placeholder id = 2

See Also

SkRefCnt

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sk_sp<SkData> serialize(const SkSerialProcs* procs = nullptr)const

Returns storage containing SkData describing SkPicture, using optional custom encoders.

procs->fPictureProc permits supplying a custom function to encode SkPicture. If procs->fPictureProc is nullptr, default encoding is used. procs->fPictureCtx may be used to provide user context to procs->fPictureProc; procs->fPictureProc is called with a pointer to SkPicture and user context.

Parameters

procs

custom serial data encoders; may be nullptr

Return Value

storage containing serialized SkPicture

Example

See Also

MakeFromData SkData SkSerialProcs

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void serialize(SkWStream* stream, const SkSerialProcs* procs = nullptr)const

Writes picture to stream, using optional custom encoders.

procs->fPictureProc permits supplying a custom function to encode SkPicture. If procs->fPictureProc is nullptr, default encoding is used. procs->fPictureCtx may be used to provide user context to procs->fPictureProc; procs->fPictureProc is called with a pointer to SkPicture and user context.

Parameters

stream	writable serial data stream
procs	custom serial data encoders; may be nullptr

Example

See Also

MakeFromStream SkWStream SkSerialProcs

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static sk_sp<SkPicture> MakePlaceholder(SkRect cull)

Returns a placeholder SkPicture. Result does not draw, and contains only cull SkRect, a hint of its bounds. Result is immutable; it cannot be changed later. Result identifier is unique.

Returned placeholder can be intercepted during playback to insert other commands into SkCanvas draw stream.

Parameters

cull	placeholder dimensions

Return Value

placeholder with unique identifier

Example

See Also

MakeFromStream MakeFromData uniqueID

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virtual int approximateOpCount() const = 0

Returns the approximate number of operations in SkPicture. Returned value may be greater or less than the number of SkCanvas calls recorded: some calls may be recorded as more than one operation, other calls may be optimized away.

Return Value

approximate operation count

Example

See Also

approximateBytesUsed

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virtual size_t approximateBytesUsed() const = 0

Returns the approximate byte size of SkPicture. Does not include large objects referenced by SkPicture.

Return Value

approximate size

Example

See Also

approximateOpCount