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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef CHROME_BROWSER_UI_COCOA_PANELS_MOUSE_DRAG_CONTROLLER_H_ | |
6 #define CHROME_BROWSER_UI_COCOA_PANELS_MOUSE_DRAG_CONTROLLER_H_ | |
7 | |
8 #import <Cocoa/Cocoa.h> | |
9 | |
10 // When Drag is cancelled by hitting ESC key, we may still receive | |
11 // the mouseDragged events but should ignore them until the mouse button is | |
12 // released. Use these simple states to track this condition. | |
13 enum PanelDragState { | |
14 PANEL_DRAG_CAN_START, // Mouse key went down, drag may be started. | |
15 PANEL_DRAG_IN_PROGRESS, | |
16 PANEL_DRAG_SUPPRESSED // Ignore drag events until PANEL_DRAG_CAN_START. | |
17 }; | |
18 | |
19 @class MouseDragController; | |
20 | |
21 @protocol MouseDragControllerClient | |
22 // Called on initial mouseDown. Followed by dragStarted/dragProgress/dragEnded | |
23 // (which can be skipped if the drag didn't start) and then by cleanupAfterDrag. | |
24 - (void)prepareForDrag; | |
25 | |
26 // Called wehen drag threshold was exceeded and actual drag should start. | |
27 // Note that the drag is processed using a local nested message loop. | |
28 // |initialMouseLocation| is in containing NSWindow's coordinates. | |
29 - (void)dragStarted:(NSPoint)initialMouseLocation; | |
30 | |
31 // Called 0 to multiple times between dragStarted and dragEnded, to report | |
32 // current mouse location. |mouseLocation| is in window coordinates. | |
33 - (void)dragProgress:(NSPoint)mouseLocation; | |
34 | |
35 - (void)dragEnded:(BOOL)cancelled; | |
36 | |
37 // Always complements prepareForDrag. Clients which create a MouseDragController | |
38 // in their mouseDown may release it in this method. | |
39 - (void)cleanupAfterDrag; | |
40 @end | |
41 | |
42 // This class encapsulates the mouse drag start/progress/termination logic, | |
43 // including having a threashold before actually starting a drag and termination | |
44 // of the drag on ESC, mouseUp and other operations. It also hosts the nested | |
45 // message loop that is used during the drag operation. | |
46 // | |
47 // The client of the controller should be a NSView implementing | |
48 // MouseDragControllerClient protocol. The client simply delegates mouse events | |
49 // to the controller, and controller invokes higher-level | |
50 // dragStarted/dragProgress/dragEnded callbacks on the client. | |
51 // The controller can be created in initial mouseDown and then released in the | |
52 // cleanupAfterDrag callback, or it can be preallocated and used across multiple | |
53 // drag operations. | |
54 // | |
55 // The pattern of usage: | |
56 // Lets say MyView is a NSView <MouseDragControllerClient> | |
57 // | |
58 // First, create an instance of MouseDragController and init it: | |
59 // dragController_.reset([[MouseDragController alloc] initWithClient:self]); | |
60 // then delegate mouse messages to it: | |
61 // | |
62 // - (void)mouseDown:(NSEvent*)event { | |
63 // if (needToStartADrag(event)) | |
64 // [dragController_ mouseDown:event]; | |
65 // } | |
66 // | |
67 // - (void)mouseDragged:(NSEvent*)event { | |
68 // [dragController_ mouseDragged:event]; | |
69 // } | |
70 // | |
71 // - (void)mouseUp:(NSEvent*)event { | |
72 // [dragController_ mouseUp:event]; | |
73 // } | |
74 // | |
75 // That's it. When user starts a drag, the client's callbacks will be invoked. | |
76 | |
77 @interface MouseDragController : NSObject { | |
78 @private | |
79 NSPoint initialMouseLocation_; // In NSWindow's coordinate system. | |
80 PanelDragState dragState_; | |
81 NSView<MouseDragControllerClient>* client_; // Weak, owns this object. | |
82 }; | |
83 | |
84 - (MouseDragController*) | |
85 initWithClient:(NSView<MouseDragControllerClient>*)client; | |
86 | |
87 // Accessors. | |
88 - (NSView<MouseDragControllerClient>*)client; | |
89 - (NSPoint)initialMouseLocation; | |
90 | |
91 // These should be called from corresponding methods of hosting NSView. | |
92 - (void)mouseDown:(NSEvent*)event; | |
93 - (void)mouseDragged:(NSEvent*)event; | |
94 - (void)mouseUp:(NSEvent*)event; | |
95 @end | |
96 | |
97 #endif // CHROME_BROWSER_UI_COCOA_PANELS_MOUSE_DRAG_CONTROLLER_H_ | |
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