Make SkOSWindow return the sample count and stencil bit count for its GL context.

src/views/mac/SkNSView.mm

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #import "SkNSView.h"
 #include "SkCanvas.h"
@@ skipping 273 matching lines @@
         msaaAttributes[kAttributeCount + 1] = kCGLPFAMultisample;
         msaaAttributes[kAttributeCount + 2] = kCGLPFASamples;
         msaaAttributes[kAttributeCount + 3] =
                                     (CGLPixelFormatAttribute)msaaSampleCount;
         msaaAttributes[kAttributeCount + 4] = (CGLPixelFormatAttribute)0;
         CGLChoosePixelFormat(msaaAttributes, &format, &npix);
     }
     if (!npix) {
         CGLChoosePixelFormat(attributes, &format, &npix);
     }
-    
     CGLContextObj ctx;
     CGLCreateContext(format, NULL, &ctx);
     CGLDestroyPixelFormat(format);
     
     static const GLint interval = 1;
     CGLSetParameter(ctx, kCGLCPSwapInterval, &interval);
     CGLSetCurrentContext(ctx);
     return ctx;
 }
 }
 
 - (void)viewDidMoveToWindow {
     [super viewDidMoveToWindow];
     
     //Attaching view to fGLContext requires that the view to be part of a window,
     //and that the NSWindow instance must have a CoreGraphics counterpart (or 
     //it must NOT be deferred or should have been on screen at least once)
     if ([fGLContext view] != self && nil != self.window) {
         [fGLContext setView:self];
     }
 }
 - (bool)attach:(SkOSWindow::SkBackEndTypes)attachType
-        withMSAASampleCount:(int) sampleCount {
+        withMSAASampleCount:(int) sampleCount
+        andGetInfo:(SkOSWindow::AttachmentInfo*) info {
     if (nil == fGLContext) {
         CGLContextObj ctx = createGLContext(sampleCount);
         fGLContext = [[NSOpenGLContext alloc] initWithCGLContextObj:ctx];
         CGLReleaseContext(ctx);
         if (NULL == fGLContext) {
             return false;
         }
         [fGLContext setView:self];
     }
-    
+
     [fGLContext makeCurrentContext];
-    
+    CGLPixelFormatObj format = CGLGetPixelFormat((CGLContextObj)[fGLContext CGLContextObj]);
+    CGLDescribePixelFormat(format, 0, kCGLPFASamples, &info->fSampleCount);
+    CGLDescribePixelFormat(format, 0, kCGLPFAStencilSize, &info->fStencilBits);
     glViewport(0, 0, (int) self.bounds.size.width, (int) self.bounds.size.width);
     glClearColor(0, 0, 0, 0);
     glClearStencil(0);
     glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
     return true;
 }
 
 - (void)detach {
     [fGLContext release];
     fGLContext = nil;
 }
 
 - (void)present {
     if (nil != fGLContext) {
         [fGLContext flushBuffer];
     }
 }
 @end