[Mac] Refactor the logic of tab dragging out of TabView and into a new helper.

chrome/browser/ui/cocoa/tabs/tab_strip_drag_controller.h

+// Copyright (c) 2011 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.
+
+#ifndef CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_DRAG_CONTROLLER_H_
+#define CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_DRAG_CONTROLLER_H_
+#pragma once
+
+#import <Cocoa/Cocoa.h>
+#include <map>
+
+@class TabController;
+@class TabStripController;
+@class TabWindowController;
+
+////////////////////////////////////////////////////////////////////////////////
+
+// This protocol is used to carry mouse events to the TabStripDragController,
+// which manages the logic for actually dragging tabs.
+@protocol TabDraggingEventTarget
+
+// Returns YES if the tab represented by the controller can be dragged.
+- (BOOL)tabCanBeDragged:(TabController*)tab;
+
+// Initiates a dragging session with a mouseDown event. The tab controller
+// passed here is the one used for the rest of the dragging session.
+- (void)maybeStartDrag:(NSEvent*)event forTab:(TabController*)tab;
+
+// Updates the dragging state with a mouseDragged event.
+- (void)continueDrag:(NSEvent*)event;
+
+// Ends a dragging session with a mouseUp event.
+- (void)endDrag:(NSEvent*)event;
+
+@end
+
+////////////////////////////////////////////////////////////////////////////////
+
+// This controller is owned by the TabStripController and is used to delegate
+// all the logic for tab dragging from the TabView's events.
+@interface TabStripDragController : NSObject<TabDraggingEventTarget> {
+ @private
+  TabStripController* tabStrip_;  // Weak; owns this.
+
+  // These are released on mouseUp:
+  BOOL moveWindowOnDrag_;  // Set if the only tab of a window is dragged.
+  BOOL tabWasDragged_;  // Has the tab been dragged?
+  BOOL draggingWithinTabStrip_;  // Did drag stay in the current tab strip?
+  BOOL chromeIsVisible_;
+
+  NSTimeInterval tearTime_;  // Time since tear happened
+  NSPoint tearOrigin_;  // Origin of the tear rect
+  NSPoint dragOrigin_;  // Origin point of the drag
+  // TODO(alcor): these references may need to be strong to avoid crashes

[pink (ping after 24hrs), 2011/06/03 14:24:49]

you can probably remove this TODO at this point.

+  // due to JS closing windows
+  TabWindowController* sourceController_;  // weak. controller starting the drag
+  NSWindow* sourceWindow_;  // weak. The window starting the drag
+  NSRect sourceWindowFrame_;
+  NSRect sourceTabFrame_;
+
+  TabController* draggedTab_;  // weak. The tab controller being dragged.
+
+  TabWindowController* draggedController_;  // weak. Controller being dragged.
+  NSWindow* dragWindow_;  // weak. The window being dragged
+  NSWindow* dragOverlay_;  // weak. The overlay being dragged
+  // Cache workspace IDs per-drag because computing them on 10.5 with
+  // CGWindowListCreateDescriptionFromArray is expensive.
+  // resetDragControllers clears this cache.
+  //
+  // TODO(davidben): When 10.5 becomes unsupported, remove this.
+  std::map<CGWindowID, int> workspaceIDCache_;
+
+  TabWindowController* targetController_;  // weak. Controller being targeted
+}
+
+// Designated initializer.
+- (id)initWithTabStripController:(TabStripController*)controller;
+
+// TabDraggingEventTarget methods are also implemented.
+
+@end
+
+#endif  // CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_DRAG_CONTROLLER_H_