image_buffer.js revision 5821806d5e7f356e8fa4b058a389a808ea183019 
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/**
6 * A stack of overlays that display itself and handle mouse events.
7 * TODO(kaznacheev) Consider disbanding this class and moving
8 * the functionality to individual objects that display anything or handle
9 * mouse events.
10 * @constructor
11 */
12function ImageBuffer() {
13  this.overlays_ = [];
14}
15
16//TODO(JSDOC)
17ImageBuffer.prototype.addOverlay = function(overlay) {
18  var zIndex = overlay.getZIndex();
19  // Store the overlays in the ascending Z-order.
20  var i;
21  for (i = 0; i != this.overlays_.length; i++) {
22    if (zIndex < this.overlays_[i].getZIndex()) break;
23  }
24  this.overlays_.splice(i, 0, overlay);
25};
26
27//TODO(JSDOC)
28ImageBuffer.prototype.removeOverlay = function(overlay) {
29  for (var i = 0; i != this.overlays_.length; i++) {
30    if (this.overlays_[i] == overlay) {
31      this.overlays_.splice(i, 1);
32      return;
33    }
34  }
35  throw new Error('Cannot remove overlay ' + overlay);
36};
37
38/**
39 * Draws overlays in the ascending Z-order.
40 */
41ImageBuffer.prototype.draw = function() {
42  for (var i = 0; i != this.overlays_.length; i++) {
43    this.overlays_[i].draw();
44  }
45};
46
47/**
48 * Searches for a cursor style in the descending Z-order.
49 * @param {number} x X coordinate for cursor.
50 * @param {number} y Y coordinate for cursor.
51 * @param {boolean} mouseDown If mouse button is down.
52 * @return {String} A value for style.cursor CSS property.
53 */
54ImageBuffer.prototype.getCursorStyle = function(x, y, mouseDown) {
55  for (var i = this.overlays_.length - 1; i >= 0; i--) {
56    var style = this.overlays_[i].getCursorStyle(x, y, mouseDown);
57    if (style) return style;
58  }
59  return 'default';
60};
61
62/**
63 * Searches for a click handler in the descending Z-order.
64 * @param {number} x X coordinate for click event.
65 * @param {number} y Y coordinate for click event.
66 * @return {Boolean} True if handled.
67 */
68ImageBuffer.prototype.onClick = function(x, y) {
69  for (var i = this.overlays_.length - 1; i >= 0; i--) {
70    if (this.overlays_[i].onClick(x, y)) return true;
71  }
72  return false;
73};
74
75/**
76 * Searches for a drag handler in the descending Z-order.
77 * @param {number} x Event X coordinate.
78 * @param {number} y Event Y coordinate.
79 * @param {boolean} touch True if it's a touch event, false if mouse.
80 * @return {function(number,number)} A function to be called on mouse drag.
81 */
82ImageBuffer.prototype.getDragHandler = function(x, y, touch) {
83  for (var i = this.overlays_.length - 1; i >= 0; i--) {
84    var handler = this.overlays_[i].getDragHandler(x, y, touch);
85    if (handler)
86      return handler;
87  }
88  return null;
89};
90
91/**
92 * Searches for an action for the double tap enumerating
93 * layers in the descending Z-order.
94 * @param {number} x X coordinate of the event.
95 * @param {number} y Y coordinate of the event.
96 * @return {ImageBuffer.DoubleTapAction} Action to perform as result.
97 */
98ImageBuffer.prototype.getDoubleTapAction = function(x, y) {
99  for (var i = this.overlays_.length - 1; i >= 0; i--) {
100    var action = this.overlays_[i].getDoubleTapAction(x, y);
101    if (action != ImageBuffer.DoubleTapAction.NOTHING)
102      return action;
103  }
104  return ImageBuffer.DoubleTapAction.NOTHING;
105};
106
107/**
108 * Possible double tap actions.
109 * @enum
110 */
111ImageBuffer.DoubleTapAction = {
112  NOTHING: 0,
113  COMMIT: 1,
114  CANCEL: 2
115};
116
117/**
118 * ImageBuffer.Overlay is a pluggable extension that modifies the outlook
119 * and the behavior of the ImageBuffer instance.
120 * @class
121 */
122//TODO(JSDOC)
123ImageBuffer.Overlay = function() {};
124
125//TODO(JSDOC)
126ImageBuffer.Overlay.prototype.getZIndex = function() { return 0 };
127
128//TODO(JSDOC)
129ImageBuffer.Overlay.prototype.draw = function() {};
130
131//TODO(JSDOC)
132ImageBuffer.Overlay.prototype.getCursorStyle = function() { return null };
133
134//TODO(JSDOC)
135ImageBuffer.Overlay.prototype.onClick = function() { return false };
136
137//TODO(JSDOC)
138ImageBuffer.Overlay.prototype.getDragHandler = function() { return null };
139
140//TODO(JSDOC)
141ImageBuffer.Overlay.prototype.getDoubleTapAction = function(x, y) {
142  return ImageBuffer.DoubleTapAction.NOTHING;
143};
144