Mac: Add partial swap support to NSOpenGLContext path

ui/accelerated_widget_mac/io_surface_texture.mm

 // Copyright (c) 2012 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/accelerated_widget_mac/io_surface_texture.h"
 
 #include <OpenGL/CGLIOSurface.h>
 #include <OpenGL/CGLRenderers.h>
 #include <OpenGL/gl.h>
 #include <OpenGL/OpenGL.h>
@@ skipping 45 matching lines @@
       needs_gl_finish_workaround_(needs_gl_finish_workaround) {
 }
 
 IOSurfaceTexture::~IOSurfaceTexture() {
   ReleaseIOSurfaceAndTexture();
   offscreen_context_ = NULL;
   DCHECK(eviction_queue_iterator_ == eviction_queue_.Get().end());
 }
 
 bool IOSurfaceTexture::DrawIOSurface() {
-  TRACE_EVENT0("browser", "IOSurfaceTexture::DrawIOSurface");
+  return DrawIOSurfaceInternal(gfx::Rect(pixel_size_), true);
+}
+
+bool IOSurfaceTexture::DrawIOSurfaceWithDamageRect(gfx::Rect damage_rect) {
+  return DrawIOSurfaceInternal(damage_rect, false);
+}
+
+bool IOSurfaceTexture::DrawIOSurfaceInternal(
+    gfx::Rect damage_rect, bool draw_boundary) {
+  TRACE_EVENT0("browser", "IOSurfaceTexture::DrawIOSurfaceInternal");
   DCHECK(CGLGetCurrentContext());
 
   // If we have release the IOSurface, clear the screen to light grey and
   // early-out.
   if (!io_surface_) {
     glClearColor(0.9, 0.9, 0.9, 1);
     glClear(GL_COLOR_BUFFER_BIT);
     return false;
   }
 
@@ skipping 10 matching lines @@
           pixel_size_.height() - viewport_rect.height(), pixel_size_.height(),
           -1, 1);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
 
   // Draw a quad the size of the IOSurface. This should cover the full viewport.
   glColor4f(1, 1, 1, 1);
   glEnable(GL_TEXTURE_RECTANGLE_ARB);
   glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texture_);
   glBegin(GL_QUADS);
-  glTexCoord2f(0, 0);
-  glVertex2f(0, 0);
-  glTexCoord2f(pixel_size_.width(), 0);
-  glVertex2f(pixel_size_.width(), 0);
-  glTexCoord2f(pixel_size_.width(), pixel_size_.height());
-  glVertex2f(pixel_size_.width(), pixel_size_.height());
-  glTexCoord2f(0, pixel_size_.height());
-  glVertex2f(0, pixel_size_.height());
+  glTexCoord2f(damage_rect.x(), damage_rect.y());
+  glVertex2f(damage_rect.x(), damage_rect.y());
+  glTexCoord2f(damage_rect.right(), damage_rect.y());
+  glVertex2f(damage_rect.right(), damage_rect.y());
+  glTexCoord2f(damage_rect.right(), damage_rect.bottom());
+  glVertex2f(damage_rect.right(), damage_rect.bottom());
+  glTexCoord2f(damage_rect.x(), damage_rect.bottom());
+  glVertex2f(damage_rect.x(), damage_rect.bottom());
   glEnd();
   glBindTexture(GL_TEXTURE_RECTANGLE_ARB, 0);
   glDisable(GL_TEXTURE_RECTANGLE_ARB);
 
   // Workaround for issue 158469. Issue a dummy draw call with texture_ not
   // bound to a texture, in order to shake all references to the IOSurface out
   // of the driver.
   glBegin(GL_TRIANGLES);
   glEnd();
 
+  // If the viewport is larger than the texture, clear out the overflow to
+  // white.
+  if (draw_boundary) {
+    if (pixel_size_.width() < viewport_rect.width()) {
+      glBegin(GL_QUADS);
+      glVertex2f(pixel_size_.width(), 0);
+      glVertex2f(pixel_size_.width(), viewport_rect.height());
+      glVertex2f(viewport_rect.width(), viewport_rect.height());
+      glVertex2f(viewport_rect.width(), 0);
+      glEnd();
+    }
+    if (pixel_size_.height() < viewport_rect.height()) {
+      int non_surface_height = viewport_rect.height() - pixel_size_.height();
+      glBegin(GL_QUADS);
+      glVertex2f(0, 0);
+      glVertex2f(0, non_surface_height);
+      glVertex2f(pixel_size_.width(), non_surface_height);
+      glVertex2f(pixel_size_.width(), 0);
+      glEnd();
+    }
+  }
+
   if (needs_gl_finish_workaround_) {
     TRACE_EVENT0("gpu", "glFinish");
     glFinish();
   }
 
   // Check if any of the drawing calls result in an error.
   GetAndSaveGLError();
   bool result = true;
   if (gl_error_ != GL_NO_ERROR) {
     LOG(ERROR) << "GL error in DrawIOSurface: " << gl_error_;
@@ skipping 180 matching lines @@
 }
 
 // static
 base::LazyInstance<IOSurfaceTexture::EvictionQueue>
     IOSurfaceTexture::eviction_queue_;
 
 // static
 bool IOSurfaceTexture::eviction_scheduled_ = false;
 
 }  // namespace ui