Implement support for mixed sampled render targets

include/gpu/GrTypes.h

 
 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTypes_DEFINED
 #define GrTypes_DEFINED
@@ skipping 512 matching lines @@
     /**
      * Handle to the 3D API object.
      * OpenGL: Texture ID.
      */
     GrBackendObject                 fTextureHandle;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 /**
+ * Optional bitfield flags that can be set on GrBackendRenderTargetDesc (below).
+ */
+enum GrBackendRenderTargetFlags {

[bsalomon, 2015/06/10 19:57:06]

I'm wondering if it is necessary to extend wrapped render targets to support
mixed samples.

Wrapped RTs are generally less useful than wrapped textures because they can
never be as a source for a draw. It really only exists for wrapping FBO 0. Our
clients typically don't use this but instead have Skia create a texture to
render to or they provide Skia a texture ID and we create the FBO and stencil
buffers to pair with it.

Is it possible for FBO 0 to be mixed?

If there is a client for this, could we have separate stencil/color sample
counts in the descriptor and simply fail if the combo is illegal?

[Chris Dalton, 2015/06/10 20:55:56]

Mixed samples is not supported for FBO 0 so we can just take this out. It just
won't be possible to wrap a mixed render target, which is fine.

+    kNone_GrBackendRenderTargetFlags            = 0x0,
+    /**
+     * Which buffers are multisampled (color and stencil, or just stencil?).
+     * The default is both. Note that mixing multisampled and aliased buffers
+     * is only possible if NV_framebuffer_mixed_samples is available.
+     */
+    kStencilMSAAOnly_GrBackendRenderTargetFlags = 0x1,
+};
+
+GR_MAKE_BITFIELD_OPS(GrBackendRenderTargetFlags)
+
+/**
  * Gr can wrap an existing render target created by the client in the 3D API
  * with a GrRenderTarget object. The client is responsible for ensuring that the
  * underlying 3D API object lives at least as long as the GrRenderTarget object
  * wrapping it. We require the client to explicitly provide information about
  * the target, such as width, height, and pixel config rather than querying the
  * 3D API for these values. We expect these properties to be immutable even if
  * the 3D API doesn't require this (OpenGL).
  */
 
 struct GrBackendRenderTargetDesc {
     GrBackendRenderTargetDesc() { memset(this, 0, sizeof(*this)); }
+    GrBackendRenderTargetFlags      fFlags;
     int                             fWidth;         //<! width in pixels
     int                             fHeight;        //<! height in pixels
     GrPixelConfig                   fConfig;        //<! color format
     GrSurfaceOrigin                 fOrigin;        //<! pixel origin
     /**
      * The number of samples per pixel. Gr uses this to influence decisions
      * about applying other forms of anti-aliasing.
      */
     int                             fSampleCnt;
     /**
@@ skipping 56 matching lines @@
             return 4 * width * height;
     }
 }
 
 /**
  * This value translates to reseting all the context state for any backend.
  */
 static const uint32_t kAll_GrBackendState = 0xffffffff;
 
 #endif