Implement support for mixed sampled render targets

src/gpu/gl/GrGLCaps.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrGLCaps_DEFINED
 #define GrGLCaps_DEFINED
@@ skipping 47 matching lines @@
          * Instead the texture is multisampled when bound to the FBO and then resolved automatically
          * when read. It also defines an alternate value for GL_MAX_SAMPLES (which we call
          * GR_GL_MAX_SAMPLES_IMG).
          */
         kES_IMG_MsToTexture_MSFBOType,
         /**
          * GL_EXT_multisampled_render_to_texture. Same as the IMG one above but uses the standard
          * GL_MAX_SAMPLES value.
          */
         kES_EXT_MsToTexture_MSFBOType,
+        /**
+         * GL_NV_framebuffer_mixed_samples.
+         */
+        kStencil_MSFBOType,

[bsalomon, 2015/03/31 16:37:33]

Maybe we should call this something a little more descriptive.
kMixedSamples_MSFBOType?

[Chris Dalton, 2015/03/31 19:47:30]

I really like the name "MixedSamples" too. I'd like to see that to become our
default catch-phrase for things that deal with this rendering mode.

My only concern is that NV_framebuffer_mixed_samples allows for multiple color
samples as well (e.g 16:4, 4:2), whereas we are forcing the color samples to 1.
Are you guys ok with "MixedSamples" being understood within skia to mean N:1
rendering? (I am if you are)

[vbuzinov, 2015/04/02 13:10:37]

Done.

 
-        kLast_MSFBOType = kES_EXT_MsToTexture_MSFBOType
+        kLast_MSFBOType = kStencil_MSFBOType
     };
 
     enum InvalidateFBType {
         kNone_InvalidateFBType,
         kDiscard_InvalidateFBType,       //<! glDiscardFramebuffer()
         kInvalidate_InvalidateFBType,     //<! glInvalidateFramebuffer()
 
         kLast_InvalidateFBType = kInvalidate_InvalidateFBType
     };
 
@@ skipping 66 matching lines @@
      * Reports the type of MSAA FBO support.
      */
     MSFBOType msFBOType() const { return fMSFBOType; }
 
     /**
      * Does the supported MSAA FBO extension have MSAA renderbuffers?
      */
     bool usesMSAARenderBuffers() const {
         return kNone_MSFBOType != fMSFBOType &&
                kES_IMG_MsToTexture_MSFBOType != fMSFBOType &&
-               kES_EXT_MsToTexture_MSFBOType != fMSFBOType;
+               kES_EXT_MsToTexture_MSFBOType != fMSFBOType &&
+               kStencil_MSFBOType != fMSFBOType;
     }
 
     /**
      * Is the MSAA FBO extension one where the texture is multisampled when bound to an FBO and
      * then implicitly resolved when read.
      */
     bool usesImplicitMSAAResolve() const {
         return kES_IMG_MsToTexture_MSFBOType == fMSFBOType ||
                kES_EXT_MsToTexture_MSFBOType == fMSFBOType;
     }
@@ skipping 244 matching lines @@
         }
     };
 
     mutable SkTHashMap<ReadPixelsSupportedFormat, bool, ReadPixelsSupportedFormat::Hash>
         fReadPixelsSupportedCache;
 
     typedef GrDrawTargetCaps INHERITED;
 };
 
 #endif