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/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkRasterHandleAllocator_DEFINED
#define SkRasterHandleAllocator_DEFINED
#include "SkImageInfo.h"
class SkBitmap;
class SkCanvas;
class SkMatrix;
/**
* 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(...),
* skstd::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.
*/
class SK_API SkRasterHandleAllocator {
public:
virtual ~SkRasterHandleAllocator() {}
// The value that is returned to clients of the canvas that has this allocator installed.
typedef void* Handle;
struct Rec {
// When the allocation goes out of scope, this proc is called to free everything associated
// with it: the pixels, the "handle", etc. This is passed the pixel address and fReleaseCtx.
void (*fReleaseProc)(void* pixels, void* ctx);
void* fReleaseCtx; // context passed to fReleaseProc
void* fPixels; // pixels for this allocation
size_t fRowBytes; // rowbytes for these pixels
Handle fHandle; // public handle returned by SkCanvas::accessTopRasterHandle()
};
/**
* 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.
*/
virtual bool allocHandle(const SkImageInfo&, Rec*) = 0;
/**
* 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.
*/
virtual void updateHandle(Handle, const SkMatrix&, const SkIRect&) = 0;
/**
* 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.
*/
static std::unique_ptr<SkCanvas> MakeCanvas(std::unique_ptr<SkRasterHandleAllocator>,
const SkImageInfo&, const Rec* rec = nullptr);
private:
friend class SkBitmapDevice;
Handle allocBitmap(const SkImageInfo&, SkBitmap*);
};
#endif
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