Adds a bounds parameter to ui::Compositor::ReadPixels

ui/gfx/compositor/compositor_gl.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/compositor/compositor_gl.h"
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/debug/trace_event.h"
@@ skipping 540 matching lines @@
   if (debug_overdraw)
     glBlendFunc(GL_ONE, GL_ONE);
   else
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 }
 
 CompositorGL::~CompositorGL() {
   gl_context_ = NULL;
 }
 
-bool CompositorGL::ReadPixels(SkBitmap* bitmap) {
+bool CompositorGL::ReadPixels(SkBitmap* bitmap, const gfx::Rect& bounds) {
   MakeCurrent();
 
+  if (bounds.right() > size().width() || bounds.bottom() > size().height())
+    return false;
+
   bitmap->setConfig(SkBitmap::kARGB_8888_Config,
-                    size().width(),
-                    size().height());
+                    bounds.width(),
+                    bounds.height());
   bitmap->allocPixels();
   SkAutoLockPixels lock(*bitmap);
   unsigned char* pixels = static_cast<unsigned char*>(bitmap->getPixels());
 
   // Check that it's a tight pixel packing
   DCHECK_EQ(bitmap->rowBytes(),
             SkBitmap::ComputeRowBytes(bitmap->config(), bitmap->width()));
 
   GLint current_alignment = 0;
   glGetIntegerv(GL_PACK_ALIGNMENT, &current_alignment);
   glPixelStorei(GL_PACK_ALIGNMENT, 4);
-  glReadPixels(0,
-               0,
-               size().width(),
-               size().height(),
+  glReadPixels(bounds.x(),
+               size().height() - bounds.y() - bounds.height(),

[Ian Vollick, 2011/11/18 18:13:45]

I think it would be helpful to have a comment like the one in compositor_cc.cc
explaining this flip.

+               bounds.width(),
+               bounds.height(),
                GL_RGBA,
                GL_UNSIGNED_BYTE,
                pixels);
   glPixelStorei(GL_PACK_ALIGNMENT, current_alignment);
 
-  SwizzleRGBAToBGRAAndFlip(pixels, size());
+  SwizzleRGBAToBGRAAndFlip(pixels, bounds.size());
   return true;
 }
 
 void CompositorGL::MakeCurrent() {
   gl_context_->MakeCurrent(gl_surface_.get());
 }
 
 void CompositorGL::OnWidgetSizeChanged() {
 }
 
@@ skipping 38 matching lines @@
 Compositor* Compositor::Create(CompositorDelegate* owner,
                                gfx::AcceleratedWidget widget,
                                const gfx::Size& size) {
   if (SharedResourcesGL::GetInstance() == NULL)
     return NULL;
   else
     return new CompositorGL(owner, widget, size);
 }
 
 }  // namespace ui