Fix the problem that notifications and panels overlap.

chrome/browser/notifications/balloon_collection_mac.mm

 // Copyright (c) 2009 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 "chrome/browser/notifications/balloon_collection_impl.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "chrome/browser/ui/cocoa/notifications/balloon_view_bridge.h"
 
@@ skipping 17 matching lines @@
 }
 
 int BalloonCollectionImpl::Layout::HorizontalEdgeMargin() const {
   return 5;
 }
 
 int BalloonCollectionImpl::Layout::VerticalEdgeMargin() const {
   return 0;
 }
 
+gfx::Point BalloonCollectionImpl::Layout::GetLayoutOrigin() const {

[jennb, 2011/11/10 19:17:13]

Comments in the code here make the code hard to read. Can you explain once at
the start of this function? Also, seems like a mistake to say TOP_LEFT is same
as lower-right?

[jianli, 2011/11/11 00:38:30]

Done.

+  const int kVerticalSpacingBetweenBalloonAndPanel = 5;
+  int x = 0;
+  int y = 0;
+  switch (placement_) {
+    case VERTICALLY_FROM_TOP_LEFT: {
+      x = work_area_.x() + HorizontalEdgeMargin();
+      // For this placement (this corresponds to lower-right alignment due to
+      // that Mac uses a vertically reversed screen orientation), balloon needs
+      // to stay on top of left-most panels to avoid overlapping.
+      int offset = bottom_left_offset_to_move_above_panels_;
+      // Ensure that we have some sort of margin between the 1st balloon and the
+      // panel beneath it even the vertical edge margin is set to 0 on Mac.
+      if (offset && !VerticalEdgeMargin())
+        offset += kVerticalSpacingBetweenBalloonAndPanel;
+      y = work_area_.y() + VerticalEdgeMargin() + offset;
+      break;
+    }
+    case VERTICALLY_FROM_TOP_RIGHT: {
+      x = work_area_.right() - HorizontalEdgeMargin();
+      // For this placement (this corresponds to lower-right alignment due to
+      // that Mac uses a vertically reversed screen orientation), balloon needs
+      // to stay on top of right-most panels to avoid overlapping.
+      int offset = bottom_right_offset_to_move_above_panels_;
+      // Ensure that we have some sort of margin between the 1st balloon and the
+      // panel beneath it even the vertical edge margin is set to 0 on Mac.
+      if (offset && !VerticalEdgeMargin())
+        offset += kVerticalSpacingBetweenBalloonAndPanel;
+      y = work_area_.y() + VerticalEdgeMargin() + offset;
+      break;
+    }
+    case VERTICALLY_FROM_BOTTOM_LEFT:
+      x = work_area_.x() + HorizontalEdgeMargin();
+      y = work_area_.bottom() - VerticalEdgeMargin();
+      break;
+    case VERTICALLY_FROM_BOTTOM_RIGHT:
+      x = work_area_.right() - HorizontalEdgeMargin();
+      y = work_area_.bottom() - VerticalEdgeMargin();
+      break;
+    default:
+      NOTREACHED();
+      break;
+  }
+  return gfx::Point(x, y);
+}
+
 void BalloonCollectionImpl::PositionBalloons(bool reposition) {
   // Use an animation context so that all the balloons animate together.
   [NSAnimationContext beginGrouping];
   [[NSAnimationContext currentContext] setDuration:0.1f];
   PositionBalloonsInternal(reposition);
   [NSAnimationContext endGrouping];
 }
 
 void BalloonCollectionImpl::SetPositionPreference(
     PositionPreference position) {
@@ skipping 13 matching lines @@
   else
     NOTREACHED();
 
   PositionBalloons(true);
 }
 
 // static
 BalloonCollection* BalloonCollection::Create() {
   return new BalloonCollectionImpl();
 }