87 lines
3.5 KiB
C
87 lines
3.5 KiB
C
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/*
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* Copyright 2016 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkRasterHandleAllocator_DEFINED
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#define SkRasterHandleAllocator_DEFINED
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#include "SkImageInfo.h"
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class SkCanvas;
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class SkMatrix;
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/**
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* If a client wants to control the allocation of raster layers in a canvas, it should subclass
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* SkRasterHandleAllocator. This allocator performs two tasks:
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* 1. controls how the memory for the pixels is allocated
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* 2. associates a "handle" to a private object that can track the matrix/clip of the SkCanvas
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*
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* This example allocates a canvas, and defers to the allocator to create the base layer.
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*
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* std::unique_ptr<SkCanvas> canvas = SkRasterHandleAllocator::MakeCanvas(
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* SkImageInfo::Make(...),
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* skstd::make_unique<MySubclassRasterHandleAllocator>(...),
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* nullptr);
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*
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* If you have already allocated the base layer (and its handle, release-proc etc.) then you
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* can pass those in using the last parameter to MakeCanvas().
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*
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* Regardless of how the base layer is allocated, each time canvas->saveLayer() is called,
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* your allocator's allocHandle() will be called.
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*/
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class SK_API SkRasterHandleAllocator {
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public:
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virtual ~SkRasterHandleAllocator() {}
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// The value that is returned to clients of the canvas that has this allocator installed.
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typedef void* Handle;
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struct Rec {
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// When the allocation goes out of scope, this proc is called to free everything associated
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// with it: the pixels, the "handle", etc. This is passed the pixel address and fReleaseCtx.
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void (*fReleaseProc)(void* pixels, void* ctx);
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void* fReleaseCtx; // context passed to fReleaseProc
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void* fPixels; // pixels for this allocation
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size_t fRowBytes; // rowbytes for these pixels
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Handle fHandle; // public handle returned by SkCanvas::accessTopRasterHandle()
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};
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/**
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* Given a requested info, allocate the corresponding pixels/rowbytes, and whatever handle
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* is desired to give clients access to those pixels. The rec also contains a proc and context
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* which will be called when this allocation goes out of scope.
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*
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* e.g.
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* when canvas->saveLayer() is called, the allocator will be called to allocate the pixels
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* for the layer. When canvas->restore() is called, the fReleaseProc will be called.
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*/
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virtual bool allocHandle(const SkImageInfo&, Rec*) = 0;
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/**
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* Clients access the handle for a given layer by calling SkCanvas::accessTopRasterHandle().
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* To allow the handle to reflect the current matrix/clip in the canvs, updateHandle() is
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* is called. The subclass is responsible to update the handle as it sees fit.
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*/
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virtual void updateHandle(Handle, const SkMatrix&, const SkIRect&) = 0;
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/**
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* This creates a canvas which will use the allocator to manage pixel allocations, including
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* all calls to saveLayer().
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*
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* If rec is non-null, then it will be used as the base-layer of pixels/handle.
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* If rec is null, then the allocator will be called for the base-layer as well.
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*/
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static std::unique_ptr<SkCanvas> MakeCanvas(std::unique_ptr<SkRasterHandleAllocator>,
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const SkImageInfo&, const Rec* rec = nullptr);
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private:
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friend class SkBitmapDevice;
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Handle allocBitmap(const SkImageInfo&, SkBitmap*);
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};
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#endif
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