Skia
2D Graphics Library
SkRasterHandleAllocator Class Referenceabstract

If a client wants to control the allocation of raster layers in a canvas, it should subclass SkRasterHandleAllocator. More...

#include <SkRasterHandleAllocator.h>

Classes

struct  Rec
 

Public Types

typedef void * Handle
 

Public Member Functions

virtual ~SkRasterHandleAllocator ()
 
virtual bool allocHandle (const SkImageInfo &, Rec *)=0
 Given a requested info, allocate the corresponding pixels/rowbytes, and whatever handle is desired to give clients access to those pixels. More...
 
virtual void updateHandle (Handle, const SkMatrix &, const SkIRect &)=0
 Clients access the handle for a given layer by calling SkCanvas::accessTopRasterHandle(). More...
 

Static Public Member Functions

static std::unique_ptr< SkCanvasMakeCanvas (std::unique_ptr< SkRasterHandleAllocator >, const SkImageInfo &, const Rec *rec=nullptr)
 This creates a canvas which will use the allocator to manage pixel allocations, including all calls to saveLayer(). More...
 

Friends

class SkBitmapDevice
 

Detailed Description

If a client wants to control the allocation of raster layers in a canvas, it should subclass SkRasterHandleAllocator.

This allocator performs two tasks:

  1. controls how the memory for the pixels is allocated
  2. associates a "handle" to a private object that can track the matrix/clip of the SkCanvas

This example allocates a canvas, and defers to the allocator to create the base layer.

std::unique_ptr<SkCanvas> canvas = SkRasterHandleAllocator::MakeCanvas(
        SkImageInfo::Make(...),
        std::make_unique<MySubclassRasterHandleAllocator>(...),
        nullptr);

If you have already allocated the base layer (and its handle, release-proc etc.) then you can pass those in using the last parameter to MakeCanvas().

Regardless of how the base layer is allocated, each time canvas->saveLayer() is called, your allocator's allocHandle() will be called.

Member Typedef Documentation

◆ Handle

Constructor & Destructor Documentation

◆ ~SkRasterHandleAllocator()

virtual SkRasterHandleAllocator::~SkRasterHandleAllocator ( )
inlinevirtual

Member Function Documentation

◆ allocHandle()

virtual bool SkRasterHandleAllocator::allocHandle ( const SkImageInfo ,
Rec  
)
pure virtual

Given a requested info, allocate the corresponding pixels/rowbytes, and whatever handle is desired to give clients access to those pixels.

The rec also contains a proc and context which will be called when this allocation goes out of scope.

e.g. when canvas->saveLayer() is called, the allocator will be called to allocate the pixels for the layer. When canvas->restore() is called, the fReleaseProc will be called.

◆ MakeCanvas()

static std::unique_ptr<SkCanvas> SkRasterHandleAllocator::MakeCanvas ( std::unique_ptr< SkRasterHandleAllocator ,
const SkImageInfo ,
const Rec rec = nullptr 
)
static

This creates a canvas which will use the allocator to manage pixel allocations, including all calls to saveLayer().

If rec is non-null, then it will be used as the base-layer of pixels/handle. If rec is null, then the allocator will be called for the base-layer as well.

◆ updateHandle()

virtual void SkRasterHandleAllocator::updateHandle ( Handle  ,
const SkMatrix ,
const SkIRect  
)
pure virtual

Clients access the handle for a given layer by calling SkCanvas::accessTopRasterHandle().

To allow the handle to reflect the current matrix/clip in the canvs, updateHandle() is is called. The subclass is responsible to update the handle as it sees fit.

Friends And Related Function Documentation

◆ SkBitmapDevice

friend class SkBitmapDevice
friend

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