Send array of paint rects and bitmaps as opposed to a Union

chrome/common/render_messages.h

 // Copyright (c) 2006-2008 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.
 
 #ifndef CHROME_COMMON_RENDER_MESSAGES_H_
 #define CHROME_COMMON_RENDER_MESSAGES_H_
 
 #include <string>
 #include <vector>
 #include <map>
@@ skipping 140 matching lines @@
   static bool is_restore_ack(int flags) {
     return (flags & IS_RESTORE_ACK) != 0;
   }
 
   static bool is_repaint_ack(int flags) {
     return (flags & IS_REPAINT_ACK) != 0;
   }
 };
 
 struct ViewHostMsg_PaintRect_Params {
-  // The bitmap to be painted into the rect given by bitmap_rect.
+  // The bitmap to be painted into the rects given by paint_rects.
   TransportDIB::Id bitmap;
 
-  // The position and size of the bitmap.
+  // The position and size of the the bitmap relative to the view port.
   gfx::Rect bitmap_rect;
 
+  // The position and size of the rects where the bitmap has data to be
+  // painted to the view. An empty vector means that the whole bitmap has
+  // data to be painted to the view.
+  std::vector<gfx::Rect> paint_rects;
+
   // The size of the RenderView when this message was generated.  This is
   // included so the host knows how large the view is from the perspective of
   // the renderer process.  This is necessary in case a resize operation is in
   // progress.
   gfx::Size view_size;
 
   // New window locations for plugin child windows.
   std::vector<WebPluginGeometry> plugin_window_moves;
 
   // The following describes the various bits that may be set in flags:
@@ skipping 674 matching lines @@
   }
 };
 
 // Traits for ViewHostMsg_PaintRect_Params structure to pack/unpack.
 template <>
 struct ParamTraits<ViewHostMsg_PaintRect_Params> {
   typedef ViewHostMsg_PaintRect_Params param_type;
   static void Write(Message* m, const param_type& p) {
     WriteParam(m, p.bitmap);
     WriteParam(m, p.bitmap_rect);
+    WriteParam(m, p.paint_rects);
     WriteParam(m, p.view_size);
     WriteParam(m, p.plugin_window_moves);
     WriteParam(m, p.flags);
   }
   static bool Read(const Message* m, void** iter, param_type* p) {
     return
       ReadParam(m, iter, &p->bitmap) &&
       ReadParam(m, iter, &p->bitmap_rect) &&
+      ReadParam(m, iter, &p->paint_rects) &&
       ReadParam(m, iter, &p->view_size) &&
       ReadParam(m, iter, &p->plugin_window_moves) &&
       ReadParam(m, iter, &p->flags);
   }
   static void Log(const param_type& p, std::wstring* l) {
     l->append(L"(");
     LogParam(p.bitmap, l);
     l->append(L", ");
     LogParam(p.bitmap_rect, l);
     l->append(L", ");
+    LogParam(p.paint_rects, l);
+    l->append(L", ");
     LogParam(p.view_size, l);
     l->append(L", ");
     LogParam(p.plugin_window_moves, l);
     l->append(L", ");
     LogParam(p.flags, l);
     l->append(L")");
   }
 };
 
 // Traits for ViewHostMsg_ScrollRect_Params structure to pack/unpack.
@@ skipping 993 matching lines @@
   }
 };
 
 }  // namespace IPC
 
 
 #define MESSAGES_INTERNAL_FILE "chrome/common/render_messages_internal.h"
 #include "chrome/common/ipc_message_macros.h"
 
 #endif  // CHROME_COMMON_RENDER_MESSAGES_H_