SplitPanel


1   /*
2    * Copyright 2007 Google Inc.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5    * use this file except in compliance with the License. You may obtain a copy of
6    * the License at
7    * 
8    * http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations under
14   * the License.
15   */
16  package com.google.gwt.user.client.ui;
17  
18  import com.google.gwt.user.client.DOM;
19  import com.google.gwt.user.client.Element;
20  import com.google.gwt.user.client.Event;
21  
22  import java.util.Iterator  ;
23  
24  /**
25   * Abstract base class for {@link HorizontalSplitPanel} and
26   * {@link VerticalSplitPanel}.
27   */
28  abstract class SplitPanel extends Panel {
29  
30    /**
31     * Adds clipping to an element.
32     * 
33     * @param elem the element
34     */
35    static final void addElementClipping(final Element elem) {
36      DOM.setStyleAttribute(elem, "overflow", "hidden");
37    }
38  
39    /**
40     * Adds as-needed scrolling to an element.
41     * 
42     * @param elem the element
43     */
44    static final void addElementScrolling(final Element elem) {
45      DOM.setStyleAttribute(elem, "overflow", "auto");
46    }
47  
48    /**
49     * Adds zero or none css values for padding, margin and border to prevent
50     * stylesheet overrides. Returns the element for convienence to support
51     * builder pattern.
52     * 
53     * @param elem the element
54     * @return the element
55     */
56    static final Element preventElementBoxStyles(final Element elem) {
57      DOM.setIntStyleAttribute(elem, "padding", 0);
58      DOM.setIntStyleAttribute(elem, "margin", 0);
59      DOM.setStyleAttribute(elem, "border", "none");
60      return elem;
61    }
62  
63    /**
64     * Adds zero size padding to an element.
65     * 
66     * @param elem the element.
67     */
68    static final void preventElementPadding(final Element elem) {
69      DOM.setStyleAttribute(elem, "padding", "0");
70    }
71  
72    /**
73     * Sets the elements css class name.
74     * 
75     * @param elem the element
76     * @param className the class name
77     */
78    static final void setElementClassname(final Element elem,
79        final String   className) {
80      DOM.setElementProperty(elem, "className", className);
81    }
82  
83    // The enclosed widgets.
84    private final Widget[] widgets = new Widget[2];
85  
86    // The elements containing the widgets.
87    private final Element[] elements = new Element[2];
88  
89    // The element that acts as the splitter.
90    private final Element splitElem;
91  
92    // Indicates whether drag resizing is active.
93    private boolean isResizing = false;
94  
95    /**
96     * Initializes the split panel.
97     * 
98     * @param mainElem the root element for the split panel
99     * @param splitElem the element that acts as the splitter
100    * @param headElem the element to contain the top or left most widget
101    * @param tailElem the element to contain the bottom or right most widget
102    */
103   SplitPanel(Element mainElem, Element splitElem, Element headElem,
104       Element tailElem) {
105     setElement(mainElem);
106     this.splitElem = splitElem;
107     elements[0] = headElem;
108     elements[1] = tailElem;
109     sinkEvents(Event.MOUSEEVENTS);
110   }
111 
112   public void add(Widget w) {
113     if (getWidget(0) == null) {
114       setWidget(0, w);
115     } else if (getWidget(1) == null) {
116       setWidget(1, w);
117     } else {
118       throw new IllegalStateException  (
119           "A Splitter can only contain two Widgets.");
120     }
121   }
122 
123   /**
124    * Indicates whether the split panel is being resized.
125    * 
126    * @return <code>true</code> if the user is dragging the splitter,
127    *         <code>false</code> otherwise
128    */
129   public boolean isResizing() {
130     return isResizing;
131   }
132 
133   public Iterator   iterator() {
134     return WidgetIterators.createWidgetIterator(this, widgets);
135   }
136 
137   public void onBrowserEvent(Event event) {
138     switch (DOM.eventGetType(event)) {
139 
140       case Event.ONMOUSEDOWN: {
141         Element target = DOM.eventGetTarget(event);
142         if (DOM.isOrHasChild(splitElem, target)) {
143           startResizingFrom(DOM.eventGetClientX(event) - getAbsoluteLeft(),
144               DOM.eventGetClientY(event) - getAbsoluteTop());
145           DOM.eventPreventDefault(event);
146         }
147         break;
148       }
149 
150       case Event.ONMOUSEUP: {
151         stopResizing();
152         break;
153       }
154 
155       case Event.ONMOUSEMOVE: {
156         if (isResizing()) {
157           onSplitterResize(DOM.eventGetClientX(event) - getAbsoluteLeft(),
158               DOM.eventGetClientY(event) - getAbsoluteTop());
159           DOM.eventPreventDefault(event);
160         }
161         break;
162       }
163     }
164   }
165 
166   public boolean remove(Widget widget) {
167     if (widget == null) {
168       throw new IllegalArgumentException  ("Widget must not be null");
169     }
170 
171     if (widgets[0] == widget) {
172       setWidget(0, null);
173       return true;
174     } else if (widgets[1] == widget) {
175       setWidget(1, null);
176       return true;
177     }
178 
179     return false;
180   }
181 
182   /**
183    * Moves the position of the splitter.
184    * 
185    * @param size the new size of the left region in CSS units (e.g. "10px",
186    *          "1em")
187    */
188   public abstract void setSplitPosition(String   size);
189 
190   /**
191    * Gets the content element for the given index.
192    * 
193    * @param index the index of the element, only 0 and 1 are valid.
194    * @return the element
195    */
196   protected Element getElement(int index) {
197     return elements[index];
198   }
199 
200   /**
201    * Gets the element that is acting as the splitter.
202    * 
203    * @return the element
204    */
205   protected Element getSplitElement() {
206     return splitElem;
207   }
208 
209   /**
210    * Gets one of the contained widgets.
211    * 
212    * @param index the index of the widget, only 0 and 1 are valid.
213    * @return the widget
214    */
215   protected Widget getWidget(int index) {
216     return widgets[index];
217   }
218 
219   /**
220    * Sets one of the contained widgets.
221    * 
222    * @param index the index, only 0 and 1 are valid
223    * @param w the widget
224    */
225   protected final void setWidget(int index, Widget w) {
226     if (widgets[index] != null) {
227       disown(widgets[index]);
228     }
229 
230     widgets[index] = w;
231 
232     if (w != null) {
233       adopt(w, elements[index]);
234     }
235   }
236 
237   /**
238    * Called on each mouse drag event as the user is dragging the splitter.
239    * 
240    * @param x the x coordinate of the mouse relative to the panel's extent
241    * @param y the y coordinate of the mosue relative to the panel's extent
242    */
243   abstract void onSplitterResize(int x, int y);
244 
245   /**
246    * Called when the user starts dragging the splitter.
247    * 
248    * @param x the x coordinate of the mouse relative to the panel's extent
249    * @param y the y coordinate of the mouse relative to the panel's extent
250    */
251   abstract void onSplitterResizeStarted(int x, int y);
252 
253   private void startResizingFrom(int x, int y) {
254     isResizing = true;
255     onSplitterResizeStarted(x, y);
256   }
257 
258   private void stopResizing() {
259     isResizing = false;
260   }
261 }
262
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags