Add API for GrContext to recommend rendertarget sample count

src/gpu/GrContext.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrContext.h"
@@ skipping 1685 matching lines @@
     }
 
     return pr;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 bool GrContext::isConfigRenderable(GrPixelConfig config, bool withMSAA) const {
     return fGpu->caps()->isConfigRenderable(config, withMSAA);
 }
 
+int GrContext::getRecommendedSampleCount(GrPixelConfig config, SkScalar dpi) const {
+    if (!this->isConfigRenderable(config, true)) {
+        return 0;
+    }
+    int chosenSampleCount = 0;
+    if (fGpu->caps()->pathRenderingSupport()) {
+        if (dpi >= 250.0f) {
+            chosenSampleCount = 4;
+        } else {
+            chosenSampleCount = 16;
+        }
+    }
+    return GrMin(fGpu->caps()->maxSampleCount(), chosenSampleCount);

[bsalomon, 2014/03/07 18:35:36]

maybe:

return chosenSampleCount < fGpu->caps()->maxSampleCount() ? chosenSampleCount :
0

?

I think we should not recommend MSAA if we can't meet some min AA quality bar.

Otherwise lgtm (feel free to update and check CQ if you're ok with the
suggestion).

+}
+
 void GrContext::setupDrawBuffer() {
     SkASSERT(NULL == fDrawBuffer);
     SkASSERT(NULL == fDrawBufferVBAllocPool);
     SkASSERT(NULL == fDrawBufferIBAllocPool);
 
     fDrawBufferVBAllocPool =
         SkNEW_ARGS(GrVertexBufferAllocPool, (fGpu, false,
                                     DRAW_BUFFER_VBPOOL_BUFFER_SIZE,
                                     DRAW_BUFFER_VBPOOL_PREALLOC_BUFFERS));
     fDrawBufferIBAllocPool =
@@ skipping 73 matching lines @@
     }
     return path;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 #if GR_CACHE_STATS
 void GrContext::printCacheStats() const {
     fTextureCache->printStats();
 }
 #endif