Attempt to get a fix and performance back.

Originally submitted as:
http://codereview.chromium.org/386021

Reverted with:
http://codereview.chromium.org/384100

This new version only creates the tracking regions (and the associated
notifications) if the mouse is actually in the tab strip. Hoping this should
improve our startup performance.

BUG=27458, 13208, 21448
TEST=Create a pile of tabs. 
     Select a middle one. 
     Put your cursor in some other tab. 
     Hit cmd-w a couple of times 
     Watch to make sure highlights occur correctly in both the tabs and the 
     close buttons.

Review URL: http://codereview.chromium.org/385102

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@31956 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 117 insertions, 22 deletions

diff --git a/chrome/browser/cocoa/tab_strip_controller.h b/chrome/browser/cocoa/tab_strip_controller.h
index fae7831..a3b4048 100644
--- a/chrome/browser/cocoa/tab_strip_controller.h
+++ b/chrome/browser/cocoa/tab_strip_controller.h
@@ -100,6 +100,9 @@ class ToolbarModel;
   // Manages per-tab sheets.
   scoped_nsobject<GTMWindowSheetController> sheetController_;
 
+  // Is the mouse currently inside the strip;
+  BOOL mouseInside_;
+
   // GTMWindowSheetController supports only one per-tab sheet at a time.
   // Thus, keep a queue of sheets for every tab. The first element in the queue
   // is the currently visible sheet, and when this sheet is closed, the next
diff --git a/chrome/browser/cocoa/tab_strip_controller.mm b/chrome/browser/cocoa/tab_strip_controller.mm
index a971808..4dd2148 100644
--- a/chrome/browser/cocoa/tab_strip_controller.mm
+++ b/chrome/browser/cocoa/tab_strip_controller.mm
@@ -95,7 +95,7 @@ private:
 
 }  // namespace
 
-@interface TabStripController(Private)
+@interface TabStripController (Private)
 - (void)installTrackingArea;
 - (void)addSubviewToPermanentList:(NSView*)aView;
 - (void)regenerateSubviewList;
@@ -107,6 +107,8 @@ private:
 - (void)animationDidStopForController:(TabController*)controller
                              finished:(BOOL)finished;
 - (NSInteger)indexFromModelIndex:(NSInteger)index;
+- (void)mouseMoved:(NSEvent*)event;
+- (void)setTabTrackingAreasEnabled:(BOOL)enabled;
 @end
 
 // A simple view class that prevents the Window Server from dragging the area
@@ -1185,6 +1187,28 @@ private:
   [self layoutTabsWithAnimation:NO regenerateSubviews:NO];
 }
 
+// Called when the tracking areas for any given tab are updated. This allows
+// the individual tabs to update their hover states correctly.
+// Only generates the event if the cursor is in the tab strip.
+- (void)tabUpdateTracking:(NSNotification*)notification {
+  DCHECK([[notification object] isKindOfClass:[TabView class]]);
+  DCHECK(mouseInside_);
+  NSWindow* window = [tabView_ window];
+  NSPoint location = [window mouseLocationOutsideOfEventStream];
+  if (NSPointInRect(location, [tabView_ frame])) {
+    NSEvent* mouseEvent = [NSEvent mouseEventWithType:NSMouseMoved
+                                             location:location
+                                        modifierFlags:0
+                                            timestamp:0
+                                         windowNumber:[window windowNumber]
+                                              context:nil
+                                          eventNumber:0
+                                           clickCount:0
+                                             pressure:0];
+    [self mouseMoved:mouseEvent];
+  }
+}
+
 - (BOOL)inRapidClosureMode {
   return availableResizeWidth_ != kUseFullAvailableWidth;
 }
@@ -1217,6 +1241,8 @@ private:
 - (void)mouseEntered:(NSEvent*)event {
   NSTrackingArea* area = [event trackingArea];
   if ([area isEqual:trackingArea_]) {
+    mouseInside_ = YES;
+    [self setTabTrackingAreasEnabled:YES];
     [self mouseMoved:event];
   } else if ([area isEqual:newTabTrackingArea_]) {
     [newTabButton_ setImage:nsimage_cache::ImageNamed(@"newtab_h.pdf")];
@@ -1229,8 +1255,9 @@ private:
 - (void)mouseExited:(NSEvent*)event {
   NSTrackingArea* area = [event trackingArea];
   if ([area isEqual:trackingArea_]) {
+    mouseInside_ = NO;
+    [self setTabTrackingAreasEnabled:NO];
     availableResizeWidth_ = kUseFullAvailableWidth;
-
     [hoveredTab_ mouseExited:event];
     hoveredTab_ = nil;
     [self layoutTabs];
@@ -1239,6 +1266,27 @@ private:
   }
 }
 
+// Enable/Disable the tracking areas for the tabs. They are only enabled
+// when the mouse is in the tabstrip.
+- (void)setTabTrackingAreasEnabled:(BOOL)enabled {
+  NSNotificationCenter* defaultCenter = [NSNotificationCenter defaultCenter];
+  for (TabController* controller in tabArray_.get()) {
+    TabView* tabView = [controller tabView];
+    if (enabled) {
+      // Set self up to observe tabs so hover states will be correct.
+      [defaultCenter addObserver:self
+                        selector:@selector(tabUpdateTracking:)
+                            name:NSViewDidUpdateTrackingAreasNotification
+                          object:tabView];
+    } else {
+      [defaultCenter removeObserver:self
+                               name:NSViewDidUpdateTrackingAreasNotification
+                             object:tabView];
+    }
+    [tabView setTrackingEnabled:enabled];
+  }
+}
+
 // Adds the given subview to (the end of) the list of permanent subviews
 // (specified from bottom up). These subviews will always be below the
 // transitory subviews (tabs). |-regenerateSubviewList| must be called to
@@ -1254,24 +1302,30 @@ private:
 // should call |-addSubviewToPermanentList:| (or better yet, call that and then
 // |-regenerateSubviewList| to actually add it).
 - (void)regenerateSubviewList {
+  // Remove self as an observer from all the old tabs before a new set of
+  // potentially different tabs is put in place.
+  [self setTabTrackingAreasEnabled:NO];
+
   // Subviews to put in (in bottom-to-top order), beginning with the permanent
   // ones.
   NSMutableArray* subviews = [NSMutableArray arrayWithArray:permanentSubviews_];
 
   NSView* selectedTabView = nil;
   // Go through tabs in reverse order, since |subviews| is bottom-to-top.
-  for (TabController* tab in [tabArray_.get() reverseObjectEnumerator]) {
+  for (TabController* tab in [tabArray_ reverseObjectEnumerator]) {
+    NSView* tabView = [tab view];
     if ([tab selected]) {
       DCHECK(!selectedTabView);
-      selectedTabView = [tab view];
+      selectedTabView = tabView;
     } else {
-      [subviews addObject:[tab view]];
+      [subviews addObject:tabView];
     }
   }
-  if (selectedTabView)
+  if (selectedTabView) {
     [subviews addObject:selectedTabView];
-
+  }
   [tabView_ setSubviews:subviews];
+  [self setTabTrackingAreasEnabled:mouseInside_];
 }
 
 - (GTMWindowSheetController*)sheetController {
diff --git a/chrome/browser/cocoa/tab_view.h b/chrome/browser/cocoa/tab_view.h
index f36512e..249f1e3 100644
--- a/chrome/browser/cocoa/tab_view.h
+++ b/chrome/browser/cocoa/tab_view.h
@@ -56,11 +56,15 @@
   NSCellStateValue state_;
 }
 @property(assign) NSCellStateValue state;
-@property(assign, nonatomic)CGFloat hoverAlpha;
+@property(assign, nonatomic) CGFloat hoverAlpha;
 
 // Determines if the tab is in the process of animating closed. It may still
 // be visible on-screen, but should not respond to/initiate any events.
-@property(assign, nonatomic)BOOL isClosing;
+@property(assign, nonatomic) BOOL isClosing;
+
+// Enables/Disables tracking regions for the tab.
+- (void)setTrackingEnabled:(BOOL)enabled;
+
 @end
 
 #endif  // CHROME_BROWSER_COCOA_TAB_VIEW_H_
diff --git a/chrome/browser/cocoa/tab_view.mm b/chrome/browser/cocoa/tab_view.mm
index 6ad5a05..50e333c 100644
--- a/chrome/browser/cocoa/tab_view.mm
+++ b/chrome/browser/cocoa/tab_view.mm
@@ -35,24 +35,12 @@ static const NSTimeInterval kAnimationHideDuration = 0.4;
 
 - (void)awakeFromNib {
   [self setShowsDivider:NO];
-  // 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.
-  closeTrackingArea_.reset(
-      [[NSTrackingArea alloc] initWithRect:[closeButton_ bounds]
-                                   options:NSTrackingMouseEnteredAndExited |
-                                           NSTrackingActiveAlways
-                                     owner:self
-                                  userInfo:nil]);
-  [closeButton_ addTrackingArea:closeTrackingArea_.get()];
 }
 
 - (void)dealloc {
   // Cancel any delayed requests that may still be pending (drags or hover).
   [NSObject cancelPreviousPerformRequestsWithTarget:self];
-  // [self gtm_unregisterForThemeNotifications];
-  [closeButton_ removeTrackingArea:closeTrackingArea_.get()];
+  [self setTrackingEnabled:NO];
   [super dealloc];
 }
 
@@ -116,6 +104,52 @@ static const NSTimeInterval kAnimationHideDuration = 0.4;
   }
 }
 
+// Enable/Disable tracking for the closeButton.
+- (void)setTrackingEnabled:(BOOL)enabled {
+  if (enabled) {
+    // Set up the tracking rect for the close button mouseover.  Add it
+    // to the |closeButton_| view, but |self| will handle the messages.
+    // The mouseover is always enabled, because the close button works
+    // regardless of key/main/active status.
+    DCHECK(closeTrackingArea_.get() == nil);
+    closeTrackingArea_.reset(
+        [[NSTrackingArea alloc] initWithRect:[closeButton_ bounds]
+                                     options:NSTrackingMouseEnteredAndExited |
+                                             NSTrackingActiveAlways
+                                       owner:self
+                                    userInfo:nil]);
+    [closeButton_ addTrackingArea:closeTrackingArea_.get()];
+  } else {
+    if (closeTrackingArea_.get()) {
+      [closeButton_ removeTrackingArea:closeTrackingArea_.get()];
+      closeTrackingArea_.reset(nil);
+    }
+  }
+}
+
+// The tracking areas have been moved. Make sure that the close button is
+// highlighting correctly with respect to the cursor position with the new
+// tracking area locations.
+- (void)updateTrackingAreas {
+  [super updateTrackingAreas];
+  if (closeTrackingArea_.get()) {
+    // Update the close buttons if the tab has moved.
+    NSPoint mouseLoc = [[self window] mouseLocationOutsideOfEventStream];
+    mouseLoc = [self convertPointFromBase:mouseLoc];
+    NSString* name = nil;
+    if (NSPointInRect(mouseLoc, [closeButton_ frame])) {
+      name = @"close_bar_h.pdf";
+    } else {
+      name = @"close_bar.pdf";
+    }
+    NSImage* newImage = nsimage_cache::ImageNamed(name);
+    NSImage* buttonImage = [closeButton_ image];
+    if (![buttonImage isEqual:newImage]) {
+      [closeButton_ setImage:newImage];
+    }
+  }
+}
+
 // Determines which view a click in our frame actually hit. It's either this
 // view or our child close button.
 - (NSView*)hitTest:(NSPoint)aPoint {