1 /*
2  * Copyright 2011 Google Inc.
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 
8 #ifndef GrGpu_DEFINED
9 #define GrGpu_DEFINED
10 
11 #include "GrPipelineBuilder.h"
12 #include "GrProgramDesc.h"
13 #include "GrStencil.h"
14 #include "GrSwizzle.h"
15 #include "GrTextureParamsAdjuster.h"
16 #include "GrXferProcessor.h"
17 #include "SkPath.h"
18 
19 class GrBatchTracker;
20 class GrContext;
21 class GrGLContext;
22 class GrIndexBuffer;
23 class GrNonInstancedVertices;
24 class GrPath;
25 class GrPathRange;
26 class GrPathRenderer;
27 class GrPathRendererChain;
28 class GrPathRendering;
29 class GrPipeline;
30 class GrPrimitiveProcessor;
31 class GrRenderTarget;
32 class GrStencilAttachment;
33 class GrSurface;
34 class GrTexture;
35 class GrTransferBuffer;
36 class GrVertexBuffer;
37 class GrVertices;
38 
39 class GrGpu : public SkRefCnt {
40 public:
41     /**
42      * Create an instance of GrGpu that matches the specified backend. If the requested backend is
43      * not supported (at compile-time or run-time) this returns nullptr. The context will not be
44      * fully constructed and should not be used by GrGpu until after this function returns.
45      */
46     static GrGpu* Create(GrBackend, GrBackendContext, const GrContextOptions&, GrContext* context);
47 
48     ////////////////////////////////////////////////////////////////////////////
49 
50     GrGpu(GrContext* context);
51     ~GrGpu() override;
52 
getContext()53     GrContext* getContext() { return fContext; }
getContext()54     const GrContext* getContext() const { return fContext; }
55 
56     /**
57      * Gets the capabilities of the draw target.
58      */
caps()59     const GrCaps* caps() const { return fCaps.get(); }
60 
pathRendering()61     GrPathRendering* pathRendering() { return fPathRendering.get();  }
62 
63     // Called by GrContext when the underlying backend context has been destroyed.
64     // GrGpu should use this to ensure that no backend API calls will be made from
65     // here onward, including in its destructor. Subclasses should call
66     // INHERITED::contextAbandoned() if they override this.
67     virtual void contextAbandoned();
68 
69     /**
70      * The GrGpu object normally assumes that no outsider is setting state
71      * within the underlying 3D API's context/device/whatever. This call informs
72      * the GrGpu that the state was modified and it shouldn't make assumptions
73      * about the state.
74      */
75     void markContextDirty(uint32_t state = kAll_GrBackendState) { fResetBits |= state; }
76 
77     /**
78      * Creates a texture object. If kRenderTarget_GrSurfaceFlag the texture can
79      * be used as a render target by calling GrTexture::asRenderTarget(). Not all
80      * pixel configs can be used as render targets. Support for configs as textures
81      * or render targets can be checked using GrCaps.
82      *
83      * @param desc        describes the texture to be created.
84      * @param budgeted    does this texture count against the resource cache budget?
85      * @param srcData     texel data to load texture. Begins with full-size
86      *                    palette data for paletted textures. For compressed
87      *                    formats it contains the compressed pixel data. Otherwise,
88      *                    it contains width*height texels. If nullptr texture data
89      *                    is uninitialized.
90      * @param rowBytes    the number of bytes between consecutive rows. Zero
91      *                    means rows are tightly packed. This field is ignored
92      *                    for compressed formats.
93      *
94      * @return    The texture object if successful, otherwise nullptr.
95      */
96     GrTexture* createTexture(const GrSurfaceDesc& desc, SkBudgeted budgeted,
97                              const void* srcData, size_t rowBytes);
98 
99     /**
100      * Implements GrTextureProvider::wrapBackendTexture
101      */
102     GrTexture* wrapBackendTexture(const GrBackendTextureDesc&, GrWrapOwnership);
103 
104     /**
105      * Implements GrTextureProvider::wrapBackendRenderTarget
106      */
107     GrRenderTarget* wrapBackendRenderTarget(const GrBackendRenderTargetDesc&, GrWrapOwnership);
108 
109     /**
110      * Implements GrTextureProvider::wrapBackendTextureAsRenderTarget
111      */
112     GrRenderTarget* wrapBackendTextureAsRenderTarget(const GrBackendTextureDesc&, GrWrapOwnership);
113 
114     /**
115      * Creates a vertex buffer.
116      *
117      * @param size    size in bytes of the vertex buffer
118      * @param dynamic hints whether the data will be frequently changed
119      *                by either GrVertexBuffer::map() or
120      *                GrVertexBuffer::updateData().
121      *
122      * @return    The vertex buffer if successful, otherwise nullptr.
123      */
124     GrVertexBuffer* createVertexBuffer(size_t size, bool dynamic);
125 
126     /**
127      * Creates an index buffer.
128      *
129      * @param size    size in bytes of the index buffer
130      * @param dynamic hints whether the data will be frequently changed
131      *                by either GrIndexBuffer::map() or
132      *                GrIndexBuffer::updateData().
133      *
134      * @return The index buffer if successful, otherwise nullptr.
135      */
136     GrIndexBuffer* createIndexBuffer(size_t size, bool dynamic);
137 
138     /**
139      * Creates a transfer buffer.
140      *
141      * @param size      size in bytes of the index buffer
142      * @param toGpu     true if used to transfer from the cpu to the gpu
143      *                  otherwise to be used to transfer from the gpu to the cpu
144      *
145      * @return The transfer buffer if successful, otherwise nullptr.
146      */
147     GrTransferBuffer* createTransferBuffer(size_t size, TransferType type);
148 
149     /**
150      * Resolves MSAA.
151      */
152     void resolveRenderTarget(GrRenderTarget* target);
153 
154     /** Info struct returned by getReadPixelsInfo about performing intermediate draws before
155         reading pixels for performance or correctness. */
156     struct ReadPixelTempDrawInfo {
157         /** If the GrGpu is requesting that the caller do a draw to an intermediate surface then
158             this is descriptor for the temp surface. The draw should always be a rect with
159             dst 0,0,w,h. */
160         GrSurfaceDesc   fTempSurfaceDesc;
161         /** Indicates whether there is a performance advantage to using an exact match texture
162             (in terms of width and height) for the intermediate texture instead of approximate. */
163         bool            fUseExactScratch;
164         /** Swizzle to apply during the draw. This is used to compensate for either feature or
165             performance limitations in the underlying 3D API. */
166         GrSwizzle       fSwizzle;
167         /** The config that should be used to read from the temp surface after the draw. This may be
168             different than the original read config in order to compensate for swizzling. The
169             read data will effectively be in the original read config. */
170         GrPixelConfig   fReadConfig;
171     };
172 
173     /** Describes why an intermediate draw must/should be performed before readPixels. */
174     enum DrawPreference {
175         /** On input means that the caller would proceed without draw if the GrGpu doesn't request
176             one.
177             On output means that the GrGpu is not requesting a draw. */
178         kNoDraw_DrawPreference,
179         /** Means that the client would prefer a draw for performance of the readback but
180             can satisfy a straight readPixels call on the inputs without an intermediate draw.
181             getReadPixelsInfo will never set the draw preference to this value but may leave
182             it set. */
183         kCallerPrefersDraw_DrawPreference,
184         /** On output means that GrGpu would prefer a draw for performance of the readback but
185             can satisfy a straight readPixels call on the inputs without an intermediate draw. The
186             caller of getReadPixelsInfo should never specify this on intput. */
187         kGpuPrefersDraw_DrawPreference,
188         /** On input means that the caller requires a draw to do a transformation and there is no
189             CPU fallback.
190             On output means that GrGpu can only satisfy the readPixels request if the intermediate
191             draw is performed.
192           */
193         kRequireDraw_DrawPreference
194     };
195 
196     /**
197      * Used to negotiate whether and how an intermediate draw should or must be performed before
198      * a readPixels call. If this returns false then GrGpu could not deduce an intermediate draw
199      * that would allow a successful readPixels call. The passed width, height, and rowBytes,
200      * must be non-zero and already reflect clipping to the src bounds.
201      */
202     bool getReadPixelsInfo(GrSurface* srcSurface, int readWidth, int readHeight, size_t rowBytes,
203                            GrPixelConfig readConfig, DrawPreference*, ReadPixelTempDrawInfo*);
204 
205     /** Info struct returned by getWritePixelsInfo about performing an intermediate draw in order
206         to write pixels to a GrSurface for either performance or correctness reasons. */
207     struct WritePixelTempDrawInfo {
208         /** If the GrGpu is requesting that the caller upload to an intermediate surface and draw
209             that to the dst then this is the descriptor for the intermediate surface. The caller
210             should upload the pixels such that the upper left pixel of the upload rect is at 0,0 in
211             the intermediate surface.*/
212         GrSurfaceDesc   fTempSurfaceDesc;
213         /** Swizzle to apply during the draw. This is used to compensate for either feature or
214             performance limitations in the underlying 3D API. */
215         GrSwizzle       fSwizzle;
216         /** The config that should be specified when uploading the *original* data to the temp
217             surface before the draw. This may be different than the original src data config in
218             order to compensate for swizzling that will occur when drawing. */
219         GrPixelConfig   fWriteConfig;
220     };
221 
222     /**
223      * Used to negotiate whether and how an intermediate surface should be used to write pixels to
224      * a GrSurface. If this returns false then GrGpu could not deduce an intermediate draw
225      * that would allow a successful transfer of the src pixels to the dst. The passed width,
226      * height, and rowBytes, must be non-zero and already reflect clipping to the dst bounds.
227      */
228     bool getWritePixelsInfo(GrSurface* dstSurface, int width, int height,
229                             GrPixelConfig srcConfig, DrawPreference*, WritePixelTempDrawInfo*);
230 
231     /**
232      * Reads a rectangle of pixels from a render target.
233      *
234      * @param surface       The surface to read from
235      * @param left          left edge of the rectangle to read (inclusive)
236      * @param top           top edge of the rectangle to read (inclusive)
237      * @param width         width of rectangle to read in pixels.
238      * @param height        height of rectangle to read in pixels.
239      * @param config        the pixel config of the destination buffer
240      * @param buffer        memory to read the rectangle into.
241      * @param rowBytes      the number of bytes between consecutive rows. Zero
242      *                      means rows are tightly packed.
243      * @param invertY       buffer should be populated bottom-to-top as opposed
244      *                      to top-to-bottom (skia's usual order)
245      *
246      * @return true if the read succeeded, false if not. The read can fail
247      *              because of a unsupported pixel config or because no render
248      *              target is currently set.
249      */
250     bool readPixels(GrSurface* surface,
251                     int left, int top, int width, int height,
252                     GrPixelConfig config, void* buffer, size_t rowBytes);
253 
254     /**
255      * Updates the pixels in a rectangle of a surface.
256      *
257      * @param surface       The surface to write to.
258      * @param left          left edge of the rectangle to write (inclusive)
259      * @param top           top edge of the rectangle to write (inclusive)
260      * @param width         width of rectangle to write in pixels.
261      * @param height        height of rectangle to write in pixels.
262      * @param config        the pixel config of the source buffer
263      * @param buffer        memory to read pixels from
264      * @param rowBytes      number of bytes between consecutive rows. Zero
265      *                      means rows are tightly packed.
266      */
267     bool writePixels(GrSurface* surface,
268                      int left, int top, int width, int height,
269                      GrPixelConfig config, const void* buffer,
270                      size_t rowBytes);
271 
272     /**
273      * Updates the pixels in a rectangle of a surface using a GrTransferBuffer
274      *
275      * @param surface       The surface to write to.
276      * @param left          left edge of the rectangle to write (inclusive)
277      * @param top           top edge of the rectangle to write (inclusive)
278      * @param width         width of rectangle to write in pixels.
279      * @param height        height of rectangle to write in pixels.
280      * @param config        the pixel config of the source buffer
281      * @param buffer        GrTransferBuffer to read pixels from
282      * @param offset        offset from the start of the buffer
283      * @param rowBytes      number of bytes between consecutive rows. Zero
284      *                      means rows are tightly packed.
285      */
286     bool transferPixels(GrSurface* surface,
287                         int left, int top, int width, int height,
288                         GrPixelConfig config, GrTransferBuffer* buffer,
289                         size_t offset, size_t rowBytes);
290 
291     /**
292      * Clear the passed in render target. Ignores the draw state and clip.
293      */
294     void clear(const SkIRect& rect, GrColor color, GrRenderTarget* renderTarget);
295 
296 
297     void clearStencilClip(const SkIRect& rect, bool insideClip, GrRenderTarget* renderTarget);
298 
299     /**
300      * Discards the contents render target. nullptr indicates that the current render target should
301      * be discarded.
302      **/
303     virtual void discard(GrRenderTarget* = nullptr) = 0;
304 
305     /**
306      * This is can be called before allocating a texture to be a dst for copySurface. It will
307      * populate the origin, config, and flags fields of the desc such that copySurface can
308      * efficiently succeed. It should only succeed if it can allow copySurface to perform a copy
309      * that would be more effecient than drawing the src to a dst render target.
310      */
311     virtual bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) const = 0;
312 
313     // After the client interacts directly with the 3D context state the GrGpu
314     // must resync its internal state and assumptions about 3D context state.
315     // Each time this occurs the GrGpu bumps a timestamp.
316     // state of the 3D context
317     // At 10 resets / frame and 60fps a 64bit timestamp will overflow in about
318     // a billion years.
319     typedef uint64_t ResetTimestamp;
320 
321     // This timestamp is always older than the current timestamp
322     static const ResetTimestamp kExpiredTimestamp = 0;
323     // Returns a timestamp based on the number of times the context was reset.
324     // This timestamp can be used to lazily detect when cached 3D context state
325     // is dirty.
getResetTimestamp()326     ResetTimestamp getResetTimestamp() const { return fResetTimestamp; }
327 
328     virtual void buildProgramDesc(GrProgramDesc*,
329                                   const GrPrimitiveProcessor&,
330                                   const GrPipeline&) const = 0;
331 
332     // Called to perform a surface to surface copy. Fallbacks to issuing a draw from the src to dst
333     // take place at the GrDrawTarget level and this function implement faster copy paths. The rect
334     // and point are pre-clipped. The src rect and implied dst rect are guaranteed to be within the
335     // src/dst bounds and non-empty.
336     bool copySurface(GrSurface* dst,
337                      GrSurface* src,
338                      const SkIRect& srcRect,
339                      const SkIPoint& dstPoint);
340 
341     struct DrawArgs {
DrawArgsDrawArgs342         DrawArgs(const GrPrimitiveProcessor* primProc,
343                  const GrPipeline* pipeline,
344                  const GrProgramDesc* desc)
345             : fPrimitiveProcessor(primProc)
346             , fPipeline(pipeline)
347             , fDesc(desc) {
348             SkASSERT(primProc && pipeline && desc);
349         }
350         const GrPrimitiveProcessor* fPrimitiveProcessor;
351         const GrPipeline* fPipeline;
352         const GrProgramDesc* fDesc;
353     };
354 
355     void draw(const DrawArgs&, const GrVertices&);
356 
357     // Called by drawtarget when flushing.
358     // Provides a hook for post-flush actions (e.g. PLS reset and Vulkan command buffer submits).
finishDrawTarget()359     virtual void finishDrawTarget() {}
360 
361     ///////////////////////////////////////////////////////////////////////////
362     // Debugging and Stats
363 
364     class Stats {
365     public:
366 #if GR_GPU_STATS
Stats()367         Stats() { this->reset(); }
368 
reset()369         void reset() {
370             fRenderTargetBinds = 0;
371             fShaderCompilations = 0;
372             fTextureCreates = 0;
373             fTextureUploads = 0;
374             fTransfersToTexture = 0;
375             fStencilAttachmentCreates = 0;
376             fNumDraws = 0;
377         }
378 
renderTargetBinds()379         int renderTargetBinds() const { return fRenderTargetBinds; }
incRenderTargetBinds()380         void incRenderTargetBinds() { fRenderTargetBinds++; }
shaderCompilations()381         int shaderCompilations() const { return fShaderCompilations; }
incShaderCompilations()382         void incShaderCompilations() { fShaderCompilations++; }
textureCreates()383         int textureCreates() const { return fTextureCreates; }
incTextureCreates()384         void incTextureCreates() { fTextureCreates++; }
textureUploads()385         int textureUploads() const { return fTextureUploads; }
incTextureUploads()386         void incTextureUploads() { fTextureUploads++; }
transfersToTexture()387         int transfersToTexture() const { return fTransfersToTexture; }
incTransfersToTexture()388         void incTransfersToTexture() { fTransfersToTexture++; }
incStencilAttachmentCreates()389         void incStencilAttachmentCreates() { fStencilAttachmentCreates++; }
incNumDraws()390         void incNumDraws() { fNumDraws++; }
391         void dump(SkString*);
392         void dumpKeyValuePairs(SkTArray<SkString>* keys, SkTArray<double>* values);
393 
394     private:
395         int fRenderTargetBinds;
396         int fShaderCompilations;
397         int fTextureCreates;
398         int fTextureUploads;
399         int fTransfersToTexture;
400         int fStencilAttachmentCreates;
401         int fNumDraws;
402 #else
403         void dump(SkString*) {}
404         void dumpKeyValuePairs(SkTArray<SkString>*, SkTArray<double>*) {}
405         void incRenderTargetBinds() {}
406         void incShaderCompilations() {}
407         void incTextureCreates() {}
408         void incTextureUploads() {}
409         void incTransfersToTexture() {}
410         void incStencilAttachmentCreates() {}
411         void incNumDraws() {}
412 #endif
413     };
414 
stats()415     Stats* stats() { return &fStats; }
416 
417     /** Creates a texture directly in the backend API without wrapping it in a GrTexture. This is
418         only to be used for testing (particularly for testing the methods that import an externally
419         created texture into Skia. Must be matched with a call to deleteTestingOnlyTexture(). */
420     virtual GrBackendObject createTestingOnlyBackendTexture(void* pixels, int w, int h,
421                                                             GrPixelConfig config) = 0;
422     /** Check a handle represents an actual texture in the backend API that has not been freed. */
423     virtual bool isTestingOnlyBackendTexture(GrBackendObject) const = 0;
424     /** If ownership of the backend texture has been transferred pass true for abandonTexture. This
425         will do any necessary cleanup of the handle without freeing the texture in the backend
426         API. */
427     virtual void deleteTestingOnlyBackendTexture(GrBackendObject,
428                                                  bool abandonTexture = false) = 0;
429 
430     // width and height may be larger than rt (if underlying API allows it).
431     // Returns nullptr if compatible sb could not be created, otherwise the caller owns the ref on
432     // the GrStencilAttachment.
433     virtual GrStencilAttachment* createStencilAttachmentForRenderTarget(const GrRenderTarget*,
434                                                                         int width,
435                                                                         int height) = 0;
436     // clears target's entire stencil buffer to 0
437     virtual void clearStencil(GrRenderTarget* target) = 0;
438 
439     // draws an outline rectangle for debugging/visualization purposes.
440     virtual void drawDebugWireRect(GrRenderTarget*, const SkIRect&, GrColor) = 0;
441 
442     // Determines whether a texture will need to be rescaled in order to be used with the
443     // GrTextureParams. This variation is called when the caller will create a new texture using the
444     // texture provider from a non-texture src (cpu-backed image, ...).
445     bool makeCopyForTextureParams(int width, int height, const GrTextureParams&,
446                                  GrTextureProducer::CopyParams*) const;
447 
448     // Like the above but this variation should be called when the caller is not creating the
449     // original texture but rather was handed the original texture. It adds additional checks
450     // relevant to original textures that were created external to Skia via
451     // GrTextureProvider::wrap methods.
makeCopyForTextureParams(GrTexture * texture,const GrTextureParams & params,GrTextureProducer::CopyParams * copyParams)452     bool makeCopyForTextureParams(GrTexture* texture, const GrTextureParams& params,
453                                   GrTextureProducer::CopyParams* copyParams) const {
454         if (this->makeCopyForTextureParams(texture->width(), texture->height(), params,
455                                            copyParams)) {
456             return true;
457         }
458         return this->onMakeCopyForTextureParams(texture, params, copyParams);
459     }
460 
461     // This is only to be used in GL-specific tests.
glContextForTesting()462     virtual const GrGLContext* glContextForTesting() const { return nullptr; }
463 
464     // This is only to be used by testing code
resetShaderCacheForTesting()465     virtual void resetShaderCacheForTesting() const {}
466 
467 protected:
468     // Functions used to map clip-respecting stencil tests into normal
469     // stencil funcs supported by GPUs.
470     static GrStencilFunc ConvertStencilFunc(bool stencilInClip,
471                                             GrStencilFunc func);
472     static void ConvertStencilFuncAndMask(GrStencilFunc func,
473                                           bool clipInStencil,
474                                           unsigned int clipBit,
475                                           unsigned int userBits,
476                                           unsigned int* ref,
477                                           unsigned int* mask);
478 
ElevateDrawPreference(GrGpu::DrawPreference * preference,GrGpu::DrawPreference elevation)479     static void ElevateDrawPreference(GrGpu::DrawPreference* preference,
480                                       GrGpu::DrawPreference elevation) {
481         GR_STATIC_ASSERT(GrGpu::kCallerPrefersDraw_DrawPreference > GrGpu::kNoDraw_DrawPreference);
482         GR_STATIC_ASSERT(GrGpu::kGpuPrefersDraw_DrawPreference >
483                          GrGpu::kCallerPrefersDraw_DrawPreference);
484         GR_STATIC_ASSERT(GrGpu::kRequireDraw_DrawPreference >
485                          GrGpu::kGpuPrefersDraw_DrawPreference);
486         *preference = SkTMax(*preference, elevation);
487     }
488 
handleDirtyContext()489     void handleDirtyContext() {
490         if (fResetBits) {
491             this->resetContext();
492         }
493     }
494 
495     Stats                                   fStats;
496     SkAutoTDelete<GrPathRendering>          fPathRendering;
497     // Subclass must initialize this in its constructor.
498     SkAutoTUnref<const GrCaps>    fCaps;
499 
500 private:
501     // called when the 3D context state is unknown. Subclass should emit any
502     // assumed 3D context state and dirty any state cache.
503     virtual void onResetContext(uint32_t resetBits) = 0;
504 
505     // Called before certain draws in order to guarantee coherent results from dst reads.
506     virtual void xferBarrier(GrRenderTarget*, GrXferBarrierType) = 0;
507 
508     // overridden by backend-specific derived class to create objects.
509     // Texture size and sample size will have already been validated in base class before
510     // onCreateTexture/CompressedTexture are called.
511     virtual GrTexture* onCreateTexture(const GrSurfaceDesc& desc,
512                                        GrGpuResource::LifeCycle lifeCycle,
513                                        const void* srcData, size_t rowBytes) = 0;
514     virtual GrTexture* onCreateCompressedTexture(const GrSurfaceDesc& desc,
515                                                  GrGpuResource::LifeCycle lifeCycle,
516                                                  const void* srcData) = 0;
517     virtual GrTexture* onWrapBackendTexture(const GrBackendTextureDesc&, GrWrapOwnership) = 0;
518     virtual GrRenderTarget* onWrapBackendRenderTarget(const GrBackendRenderTargetDesc&,
519                                                       GrWrapOwnership) = 0;
520     virtual GrRenderTarget* onWrapBackendTextureAsRenderTarget(const GrBackendTextureDesc&,
521                                                                GrWrapOwnership) = 0;
522     virtual GrVertexBuffer* onCreateVertexBuffer(size_t size, bool dynamic) = 0;
523     virtual GrIndexBuffer* onCreateIndexBuffer(size_t size, bool dynamic) = 0;
524     virtual GrTransferBuffer* onCreateTransferBuffer(size_t size, TransferType type) = 0;
525 
526     // overridden by backend-specific derived class to perform the clear.
527     virtual void onClear(GrRenderTarget*, const SkIRect& rect, GrColor color) = 0;
528 
529 
530     // Overridden by backend specific classes to perform a clear of the stencil clip bits.  This is
531     // ONLY used by the the clip target
532     virtual void onClearStencilClip(GrRenderTarget*, const SkIRect& rect, bool insideClip) = 0;
533 
534     // overridden by backend-specific derived class to perform the draw call.
535     virtual void onDraw(const DrawArgs&, const GrNonInstancedVertices&) = 0;
536 
onMakeCopyForTextureParams(GrTexture * texture,const GrTextureParams &,GrTextureProducer::CopyParams *)537     virtual bool onMakeCopyForTextureParams(GrTexture* texture, const GrTextureParams&,
538                                             GrTextureProducer::CopyParams*) const { return false; }
539 
540     virtual bool onGetReadPixelsInfo(GrSurface* srcSurface, int readWidth, int readHeight,
541                                      size_t rowBytes, GrPixelConfig readConfig, DrawPreference*,
542                                      ReadPixelTempDrawInfo*) = 0;
543     virtual bool onGetWritePixelsInfo(GrSurface* dstSurface, int width, int height,
544                                       GrPixelConfig srcConfig, DrawPreference*,
545                                       WritePixelTempDrawInfo*) = 0;
546 
547     // overridden by backend-specific derived class to perform the surface read
548     virtual bool onReadPixels(GrSurface*,
549                               int left, int top,
550                               int width, int height,
551                               GrPixelConfig,
552                               void* buffer,
553                               size_t rowBytes) = 0;
554 
555     // overridden by backend-specific derived class to perform the surface write
556     virtual bool onWritePixels(GrSurface*,
557                                int left, int top, int width, int height,
558                                GrPixelConfig config, const void* buffer,
559                                size_t rowBytes) = 0;
560 
561     // overridden by backend-specific derived class to perform the surface write
562     virtual bool onTransferPixels(GrSurface*,
563                                   int left, int top, int width, int height,
564                                   GrPixelConfig config, GrTransferBuffer* buffer,
565                                   size_t offset, size_t rowBytes) = 0;
566 
567     // overridden by backend-specific derived class to perform the resolve
568     virtual void onResolveRenderTarget(GrRenderTarget* target) = 0;
569 
570     // overridden by backend specific derived class to perform the copy surface
571     virtual bool onCopySurface(GrSurface* dst,
572                                GrSurface* src,
573                                const SkIRect& srcRect,
574                                const SkIPoint& dstPoint) = 0;
575 
resetContext()576     void resetContext() {
577         this->onResetContext(fResetBits);
578         fResetBits = 0;
579         ++fResetTimestamp;
580     }
581 
582     ResetTimestamp                                                      fResetTimestamp;
583     uint32_t                                                            fResetBits;
584     // The context owns us, not vice-versa, so this ptr is not ref'ed by Gpu.
585     GrContext*                                                          fContext;
586 
587     friend class GrPathRendering;
588     typedef SkRefCnt INHERITED;
589 };
590 
591 #endif
592