SkPicture Reference

Picture

Class SkPicture

Constructor

SkPicture can be constructed or initialized by these functions, including C++ class constructors.

Topic Description
MakeFromData constructs Picture from data
MakeFromStream constructs Picture from stream
MakePlaceholder constructs placeholder with unique identifier

An SkPicture records drawing commands made to a canvas to be played back at a later time. This base class handles serialization and a few other miscellany.

Overview

Topic Description
Class Declarations embedded class members
Constructors functions that construct SkPicture
Functions global and class member functions

Class

SkPicture uses C++ classes to declare the public data structures and interfaces.

Topic Description
AbortCallback utility to stop picture playback

Member Function

SkPicture member functions read and modify the structure properties.

Topic Description
MakeFromData constructs Picture from data
MakeFromStream constructs Picture from stream
MakePlaceholder constructs placeholder with unique identifier
approximateBytesUsed returns approximate size
approximateOpCount returns approximate operation count
cullRect returns bounds used to record Picture
playback replays drawing commands on canvas
serialize writes Picture to data
uniqueID returns identifier for Picture

Class SkPicture::AbortCallback

Constructor

SkPicture can be constructed or initialized by these functions, including C++ class constructors.

Topic Description

Member_Function

SkPicture member functions read and modify the structure properties.

Topic Description

    class AbortCallback {
    public:
        AbortCallback() {}
        virtual

Subclasses of this can be passed to playback. During the playback of the picture, this callback will periodically be invoked. If its abort returns true, then picture playback will be interrupted. The resulting drawing is undefined, as there is no guarantee how often the callback will be invoked. If the abort happens inside some level of nested calls to save(), restore will automatically be called to return the state to the same level it was before the playback call was made.

AbortCallback

AbortCallback()

Has no effect.

Return Value

abstract class cannot be instantiated

See Also

playback


~AbortCallback

virtual

Has no effect.

See Also

playback


abort

virtual bool abort() = 0

Stops Picture playback when some condition is met. A subclass of AbortCallback provides an override for abort that can stop playback from drawing the entire picture.

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.

MakeFromStream

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

Recreates a picture that was serialized into a stream.

Parameters

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

Return Value

Picture constructed from stream data

Example

See Also

MakeFromData[2] SkPictureRecorder


MakeFromData

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

Recreates a picture that was serialized into data.

Parameters

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

Return Value

Picture constructed from data

Example

See Also

MakeFromStream SkPictureRecorder


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

Parameters

Recreates a picture that was serialized into data.
data pointer to serial data
size size of data
procs custom serial data decoders; may be nullptr

Return Value

Picture constructed from data

Example

See Also

MakeFromStream SkPictureRecorder


playback

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

Replays the drawing commands on the specified canvas. Note that this has the effect of unfurling this picture into the destination canvas. Using the SkCanvas::drawPicture entry point gives the destination canvas the option of just taking a ref.

Parameters

canvas receiver of drawing commands
callback allows interruption of playback

Example

See Also

SkCanvas::drawPicture[2][3][4]


cullRect

virtual SkRect cullRect() const = 0

Returns cull Rect for this picture. Ops recorded into this picture that attempt to draw outside the cull might not be drawn.

Return Value

bounds passed when Picture 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[2][3]


uniqueID

uint32_t uniqueID() const

Returns a non-zero value unique among all pictures.

Return Value

identifier for Picture

Example

#### Example Output ~~~~ empty picture id = 1 placeholder id = 2 ~~~~

See Also

SkRefCnt


serialize

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

Returns storage containing data describing Picture, using optional custom encoders.

Parameters

procs custom serial data encoders; may be nullptr

Return Value

storage containing serialized Picture

Example

See Also

MakeFromData[2] SkData SkSerialProcs


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

Writes picture to stream, using optional custom encoders.

Parameters

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

Example

See Also

MakeFromStream SkWStream SkSerialProcs


MakePlaceholder

static sk sp<SkPicture> MakePlaceholder(SkRect cull)

Returns a placeholder SkPicture. This placeholder does not draw anything itself. It has a distinct uniqueID (just like all Pictures) and will always be visible to SkSerialProcs.

Parameters

cull placeholder dimensions

Return Value

placeholder with unique identifier

Example

#### Example Output ~~~~ id:1 bounds:{10, 40, 80, 110} id:2 bounds:{10, 40, 80, 110} ~~~~

See Also

MakeFromStream MakeFromData[2]


approximateOpCount

virtual int approximateOpCount() const = 0

Returns the approximate number of operations in this picture. This number may be greater or less than the number of SkCanvas calls recorded: some calls may be recorded as more than one operation, or some calls may be optimized away.

Return Value

approximate operation count

Example

See Also

approximateBytesUsed


approximateBytesUsed

virtual size_t approximateBytesUsed() const = 0

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

Return Value

approximate size

Example

See Also

approximateOpCount