Mac: Fix crash when dragging tabs

chrome/browser/ui/cocoa/tabs/tab_strip_drag_controller.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.
 
 #import "chrome/browser/ui/cocoa/tabs/tab_strip_drag_controller.h"
 
 #import "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #import "base/mac/sdk_forward_declarations.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_controller.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_controller_target.h"
+#import "chrome/browser/ui/cocoa/tabs/tab_strip_view.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_view.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_window_controller.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_strip_controller.h"
 
 const CGFloat kTearDistance = 36.0;
 const NSTimeInterval kTearDuration = 0.333;
 
+// Returns whether |screenPoint| is inside the bounds of |view|.
+static BOOL PointIsInsideView(NSPoint screenPoint, NSView* view) {
+  if ([view window] == nil)
+    return NO;
+  NSPoint windowPoint = [[view window] convertScreenToBase:screenPoint];
+  NSPoint viewPoint = [view convertPoint:windowPoint fromView:nil];
+  return [view mouse:viewPoint inRect:[view bounds]];
+}
+
 @interface TabStripDragController (Private)
 - (void)resetDragControllers;
 - (NSArray*)dropTargetsForController:(TabWindowController*)dragController;
 - (void)setWindowBackgroundVisibility:(BOOL)shouldBeVisible;
 - (void)endDrag:(NSEvent*)event;
 - (void)continueDrag:(NSEvent*)event;
 @end
 
 ////////////////////////////////////////////////////////////////////////////////
 
@@ skipping 151 matching lines @@
         (tearForce > kTearDistance || !stillVisible)) {
       draggingWithinTabStrip_ = NO;
       // When you finally leave the strip, we treat that as the origin.
       dragOrigin_.x = thisPoint.x;
     } else {
       // Still dragging within the tab strip, wait for the next drag event.
       return;
     }
   }
 
-  // Do not start dragging until the user has "torn" the tab off by
-  // moving more than 3 pixels.

[Andre, 2014/03/26 01:29:31]

I think this comment is outdated.
The distance is specified by kTearDistance above.

   NSPoint thisPoint = [NSEvent mouseLocation];
 
   // Iterate over possible targets checking for the one the mouse is in.
   // If the tab is just in the frame, bring the window forward to make it
   // easier to drop something there. If it's in the tab strip, set the new
   // target so that it pops into that window. We can't cache this because we
   // need the z-order to be correct.
   NSArray* targets = [self dropTargetsForController:draggedController_];
   TabWindowController* newTarget = nil;
   for (TabWindowController* target in targets) {
     NSRect windowFrame = [[target window] frame];
     if (NSPointInRect(thisPoint, windowFrame)) {
       [[target window] orderFront:self];
-      NSRect tabStripFrame = [[target tabStripView] frame];
-      tabStripFrame.origin = [[target window]
-                              convertBaseToScreen:tabStripFrame.origin];
-      if (NSPointInRect(thisPoint, tabStripFrame)) {
+      if (PointIsInsideView(thisPoint, [target tabStripView])) {
         newTarget = target;
       }
       break;
     }
   }
 
   // If we're now targeting a new window, re-layout the tabs in the old
   // target and reset how long we've been hovering over this new one.
   if (targetController_ != newTarget) {
     [targetController_ removePlaceholder];
     targetController_ = newTarget;
     if (!newTarget) {
       tearTime_ = [NSDate timeIntervalSinceReferenceDate];
       tearOrigin_ = [dragWindow_ frame].origin;
     }
   }
 
   // Create or identify the dragged controller.
   if (!draggedController_) {
-    // We don't want to remove the source window's placeholder here because the
-    // new tab button may briefly flash in and out if we remove and add back the
-    // placeholder.
-    // Instead, we will remove the placeholder later when the target window
-    // actually changes.
-    targetController_ = sourceController_;
-
     // Detach from the current window and put it in a new window. If there are
     // no more tabs remaining after detaching, the source window is about to
     // go away (it's been autoreleased) so we need to ensure we don't reference
     // it any more. In that case the new controller becomes our source
     // controller.
     NSArray* tabs = [draggedTab_ selected] ? [tabStrip_ selectedViews]
                                            : @[ [draggedTab_ tabView] ];
     draggedController_ =
         [sourceController_ detachTabsToNewWindow:tabs
                                       draggedTab:[draggedTab_ tabView]];
 
     dragWindow_ = [draggedController_ window];
     [dragWindow_ setAlphaValue:0.0];
-    if (![sourceController_ hasLiveTabs]) {
+    if ([sourceController_ hasLiveTabs]) {
+      if (PointIsInsideView(thisPoint, [sourceController_ tabStripView])) {
+        // We don't want to remove the source window's placeholder here because
+        // the new tab button may briefly flash in and out if we remove and add
+        // back the placeholder.
+        // Instead, we will remove the placeholder later when the target window
+        // actually changes.
+        targetController_ = sourceController_;
+      } else {
+        [sourceController_ removePlaceholder];
+      }
+    } else {
+      [sourceController_ removePlaceholder];
       sourceController_ = draggedController_;
       sourceWindow_ = dragWindow_;
     }
 
     // Disable window animation before calling |orderFront:| when detaching
     // to a new window.
     NSWindowAnimationBehavior savedAnimationBehavior =
         NSWindowAnimationBehaviorDefault;
     bool didSaveAnimationBehavior = false;
     if ([dragWindow_ respondsToSelector:@selector(animationBehavior)] &&
@@ skipping 221 matching lines @@
     [[targetController_ window] makeMainWindow];
   } else {
     [dragWindow_ setAlphaValue:0.5];
     [[draggedController_ overlayWindow] setHasShadow:NO];
     [[draggedController_ window] makeMainWindow];
   }
   chromeIsVisible_ = shouldBeVisible;
 }
 
 @end