Make download items drag sources on OS X.

chrome/browser/cocoa/bookmark_button.mm

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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 "base/logging.h"
 #import "base/scoped_nsobject.h"
 #import "chrome/browser/cocoa/bookmark_button.h"
 #import "chrome/browser/cocoa/bookmark_button_cell.h"
-#import "third_party/GTM/AppKit/GTMTheme.h"
-
-namespace {
-
-// Code taken from <http://codereview.chromium.org/180036/diff/3001/3004>.
-// TODO(viettrungluu): Do we want common, standard code for drag hysteresis?
-const CGFloat kWebDragStartHysteresisX = 5.0;
-const CGFloat kWebDragStartHysteresisY = 5.0;
 
 // The opacity of the bookmark button drag image.
-const CGFloat kDragImageOpacity = 0.7;
-
-}
+static const CGFloat kDragImageOpacity = 0.7;
 
 @interface BookmarkButton(Private)
 
 // Make a drag image for the button.
 - (NSImage*)dragImage;
 
 @end  // @interface BookmarkButton(Private)
 
 @implementation BookmarkButton
 
-@synthesize draggable = draggable_;
 @synthesize delegate = delegate_;
 
-- (id)initWithFrame:(NSRect)frame {
-  if ((self = [super initWithFrame:frame])) {
-    draggable_ = YES;
-  }
-  return self;
-}
-
 // By default, NSButton ignores middle-clicks.
 - (void)otherMouseUp:(NSEvent*)event {
   [self performClick:self];
 }
 
+// Overridden from DraggableButton.
 - (void)beginDrag:(NSEvent*)event {
-  // Starting drag. Never start another drag until another mouse down.
-  mayDragStart_ = NO;
-
   if (delegate_) {
     // Ask our delegate to fill the pasteboard for us.
     NSPasteboard* pboard = [NSPasteboard pasteboardWithName:NSDragPboard];
 
     [delegate_ fillPasteboard:pboard forDragOfButton:self];
 
     // At the moment, moving bookmarks causes their buttons (like me!)
     // to be destroyed and rebuilt.  Make sure we don't go away while on
     // the stack.
     [self retain];
 
     CGFloat yAt = [self bounds].size.height;
     NSSize dragOffset = NSMakeSize(0.0, 0.0);
     [self dragImage:[self dragImage] at:NSMakePoint(0, yAt) offset:dragOffset
               event:event pasteboard:pboard source:self slideBack:YES];
 
-    // And we're done.
+    // And we're done.  
     [self autorelease];
   } else {
     // Avoid blowing up, but we really shouldn't get here.
     NOTREACHED();
   }
 }
 
 - (void)draggedImage:(NSImage*)anImage
              endedAt:(NSPoint)aPoint
            operation:(NSDragOperation)operation {
-  beingDragged_ = NO;
-  [[self cell] setHighlighted:NO];
+  [super endDrag];
 }
 
 - (NSDragOperation)draggingSourceOperationMaskForLocal:(BOOL)isLocal {
   return isLocal ? NSDragOperationCopy | NSDragOperationMove
                  : NSDragOperationCopy;
 }
 
-- (void)mouseUp:(NSEvent*)theEvent {
-  // Make sure that we can't start a drag until we see a mouse down again.
-  mayDragStart_ = NO;
-
-  // This conditional is never true (DnD loops in Cocoa eat the mouse
-  // up) but I added it in case future versions of Cocoa do unexpected
-  // things.
-  if (beingDragged_) {
-    NOTREACHED();
-    return [super mouseUp:theEvent];
-  }
-
-  // There are non-drag cases where a mouseUp: may happen
-  // (e.g. mouse-down, cmd-tab to another application, move mouse,
-  // mouse-up).  So we check.
-  NSPoint viewLocal = [self convertPoint:[theEvent locationInWindow]
-                                fromView:[[self window] contentView]];
-  if (NSPointInRect(viewLocal, [self bounds])) {
-    [self performClick:self];
-  } else {
-    [[self cell] setHighlighted:NO];
-  }
-}
-
-// Mimic "begin a click" operation visually.  Do NOT follow through
-// with normal button event handling.
-- (void)mouseDown:(NSEvent*)theEvent {
-  mayDragStart_ = YES;
-  [[self cell] setHighlighted:YES];
-  initialMouseDownLocation_ = [theEvent locationInWindow];
-}
-
-// Return YES if we have crossed a threshold of movement after
-// mouse-down when we should begin a drag.  Else NO.
-- (BOOL)hasCrossedDragThreshold:(NSEvent*)theEvent {
-  NSPoint currentLocation = [theEvent locationInWindow];
-  if ((abs(currentLocation.x - initialMouseDownLocation_.x) >
-       kWebDragStartHysteresisX) ||
-      (abs(currentLocation.y - initialMouseDownLocation_.y) >
-       kWebDragStartHysteresisY)) {
-    return YES;
-  } else {
-    return NO;
-  }
-}
-
-- (void)mouseDragged:(NSEvent*)theEvent {
-  if (beingDragged_) {
-    [super mouseDragged:theEvent];
-  } else if (draggable_ && mayDragStart_ &&
-             [self hasCrossedDragThreshold:theEvent]) {
-    [self beginDrag:theEvent];
-  }
-}
-
 @end
 
 @implementation BookmarkButton(Private)
 
 - (NSImage*)dragImage {
   NSRect bounds = [self bounds];
 
   // Grab the image from the screen and put it in an |NSImage|. We can't use
   // this directly since we need to clip it and set its opacity. This won't work
   // if the source view is clipped. Fortunately, we don't display clipped
@@ skipping 18 matching lines @@
   [image drawAtPoint:NSMakePoint(0, 0)
             fromRect:NSMakeRect(0, 0, NSWidth(bounds), NSHeight(bounds))
            operation:NSCompositeSourceOver
             fraction:kDragImageOpacity];
 
   [dragImage unlockFocus];
   return dragImage;
 }
 
 @end  // @implementation BookmarkButton(Private)