Set willReadFragmentPosition on XP when doing a DstCopy.

src/gpu/GrXferProcessor.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrXferProcessor.h"
 #include "gl/GrGLCaps.h"
 
 GrXferProcessor::GrXferProcessor() : fWillReadDstColor(false), fDstCopyTextureOffset() {
 }
 
 GrXferProcessor::GrXferProcessor(const GrDeviceCoordTexture* dstCopy, bool willReadDstColor)
     : fWillReadDstColor(willReadDstColor)
     , fDstCopyTextureOffset() {
     if (dstCopy && dstCopy->texture()) {
         fDstCopy.reset(dstCopy->texture());
         fDstCopyTextureOffset = dstCopy->offset();
         this->addTextureAccess(&fDstCopy);

[robertphillips, 2015/04/07 14:12:58]

So we always read the frag position?

[egdaniel, 2015/04/07 14:18:11]

if we have made an actual dstCopy then we will always read it.

[bsalomon, 2015/04/07 14:18:40]

If we're reading a dst copy, we use the fragment position as texture coords.

lgtm

+        this->setWillReadFragmentPosition();
     }
 }
 
 void GrXferProcessor::getGLProcessorKey(const GrGLCaps& caps, GrProcessorKeyBuilder* b) const {
     uint32_t key = this->willReadDstColor() ? 0x1 : 0x0;
     if (this->getDstCopyTexture() &&
         kTopLeft_GrSurfaceOrigin == this->getDstCopyTexture()->origin()) {
         key |= 0x2;
     }
     b->add32(key);
@@ skipping 18 matching lines @@
     }
 #endif
     return this->onCreateXferProcessor(caps, colorPOI, coveragePOI, dstCopy);
 }
 
 bool GrXPFactory::willNeedDstCopy(const GrDrawTargetCaps& caps, const GrProcOptInfo& colorPOI,
                                   const GrProcOptInfo& coveragePOI) const {
     return (this->willReadDstColor(caps, colorPOI, coveragePOI) && !caps.dstReadInShaderSupport());
 }