Adds mouseover images to the close tab button on Mac....

chrome/browser/cocoa/tab_view.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/cocoa/tab_controller.h"
 #include "chrome/browser/cocoa/tab_view.h"
 #include "chrome/browser/cocoa/tab_window_controller.h"
 
 @implementation TabView
 
 - (id)initWithFrame:(NSRect)frame {
   self = [super initWithFrame:frame];
   if (self) {
     // TODO(alcor): register for theming, either here or the cell
     // [self gtm_registerForThemeNotifications];
   }
   return self;
 }
 
+- (void)awakeFromNib {
+  // Set up the tracking rect for the close button mouseover.  Add it
+  // to the |closeButton_| view, but we'll handle the message ourself.
+  // The mouseover is always enabled, because the close button works
+  // regardless of key/main/active status.
+  trackingArea_.reset(
+      [[NSTrackingArea alloc] initWithRect:[closeButton_ bounds]
+                                   options:NSTrackingMouseEnteredAndExited |
+                                           NSTrackingActiveAlways
+                                     owner:self

[pink (ping after 24hrs), 2009/05/27 13:07:59]

are you sure this doesn't set up an ownership cycle? Can you verify that dealloc
is still getting called on TabView?

[rohitrao (ping after 24h), 2009/05/27 23:58:50]

I added logging in dealloc and verified that dealloc is getting called for every
tab.

More reassuringly, I also added logging in a retain method and verified that
TabView is not being retained by NSTrackingArea.

+                                  userInfo:nil]);
+  [closeButton_ addTrackingArea:trackingArea_.get()];
+}
+
 - (void)dealloc {
   // [self gtm_unregisterForThemeNotifications];
+  [closeButton_ removeTrackingArea:trackingArea_.get()];
   [super dealloc];
 }
 
 // Overridden so that mouse clicks come to this view (the parent of the
 // hierarchy) first. We want to handle clicks and drags in this class and
 // leave the background button for display purposes only.
 - (BOOL)acceptsFirstMouse:(NSEvent *)theEvent {
   return YES;
 }
 
+- (void)mouseEntered:(NSEvent *)theEvent {
+  // We only set up one tracking area, so we know any mouseEntered:
+  // messages are for close button mouseovers.
+  [closeButton_ setImage:[NSImage imageNamed:@"close_bar_h"]];
+}
+
+- (void)mouseExited:(NSEvent *)theEvent {
+  // We only set up one tracking area, so we know any mouseExited:
+  // messages are for close button mouseovers.
+  [closeButton_ setImage:[NSImage imageNamed:@"close_bar"]];
+}
+
 // Determines which view a click in our frame actually hit. It's either this
 // view or our child close button.
 - (NSView *)hitTest:(NSPoint)aPoint {
   NSPoint viewPoint = [self convertPoint:aPoint fromView:[self superview]];
   NSRect frame = [self frame];
 
   // Reduce the width of the hit rect slightly to remove the overlap
   // between adjacent tabs.  The drawing code in TabCell has the top
   // corners of the tab inset by height*2/3, so we inset by half of
   // that here.  This doesn't completely eliminate the overlap, but it
@@ skipping 283 matching lines @@
 }
 
 - (void)otherMouseUp:(NSEvent*) theEvent {
   // Support middle-click-to-close.
   if ([theEvent buttonNumber] == 2) {
     [controller_ closeTab:self];
   }
 }
 
 @end