AutoscrollSupport


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11   * If applicable, add the following below the CDDL Header, with the fields
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15   * The Original Software is NetBeans. The Initial Developer of the Original
16   * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
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19  package org.openide.explorer.view;
20  
21  import java.awt.Component  ;
22  import java.awt.Insets  ;
23  import java.awt.Point  ;
24  import java.awt.dnd.Autoscroll  ;
25  
26  import javax.swing.JViewport  ;
27  
28  
29  /** The support for autoscrolling in components contained in
30  * the viewport.
31  *
32  * @author Dafe Simonek
33  */
34  final class AutoscrollSupport extends Object   implements Autoscroll   {
35      // Attributes
36  
37      /** The component which we support with autoscrolling */
38      Component   comp;
39  
40      /** The viewport containing asociated component */
41      JViewport   viewport;
42  
43      /** The insets where autoscrolling is active */
44      Insets   insets;
45  
46      /** Base sizes of scrolling during one autoscroll operation */
47      Insets   scrollUnits;
48  
49      /** Insets to return from getAutoscrollInsets - insets
50      * where autoscroll could potencionally occur */
51      Insets   autoscrollInsets;
52  
53      /** Creates a support for given component with given insets
54      * where autoscrolling is active */
55      AutoscrollSupport(Component   comp, Insets   insets) {
56          this.comp = comp;
57          this.insets = insets;
58          this.scrollUnits = insets;
59      }
60  
61      /** Performs autoscroll operation.
62      */
63      public void autoscroll(Point   cursorLoc) {
64          JViewport   viewport = getViewport();
65  
66          if (viewport == null) {
67              return;
68          }
69  
70          Point   viewPos = viewport.getViewPosition();
71          int viewHeight = viewport.getExtentSize().height;
72          int viewWidth = viewport.getExtentSize().width;
73  
74          // perform scrolling
75          if ((cursorLoc.y - viewPos.y) < insets.top) {
76              // scroll up
77              viewport.setViewPosition(new Point  (viewPos.x, Math.max(viewPos.y - scrollUnits.top, 0)));
78          } else if (((viewPos.y + viewHeight) - cursorLoc.y) < insets.bottom) {
79              // scroll down
80              viewport.setViewPosition(
81                  new Point  (viewPos.x, Math.min(viewPos.y + scrollUnits.bottom, comp.getHeight() - viewHeight))
82              );
83          } else if ((cursorLoc.x - viewPos.x) < insets.left) {
84              // scroll left
85              viewport.setViewPosition(new Point  (Math.max(viewPos.x - scrollUnits.left, 0), viewPos.y));
86          } else if (((viewPos.x + viewWidth) - cursorLoc.x) < insets.right) {
87              // scroll right
88              viewport.setViewPosition(
89                  new Point  (Math.min(viewPos.x + scrollUnits.right, comp.getWidth() - viewWidth), viewPos.y)
90              );
91          }
92      }
93  
94      public Insets   getAutoscrollInsets() {
95          if (autoscrollInsets == null) {
96              int height = comp.getHeight();
97              int width = comp.getWidth();
98              autoscrollInsets = new Insets  (height, width, height, width);
99          }
100 
101         return autoscrollInsets;
102     }
103 
104     /** @return insets where autoscroll is active
105     */
106     public Insets   getInsets() {
107         return insets;
108     }
109 
110     /** Sets new active autoscroll insets
111     */
112     public void setInsets(Insets   insets) {
113         this.insets = insets;
114     }
115 
116     /** @return Scroll units for one autoscroll operation.
117     */
118     public Insets   getScrollUnits() {
119         return scrollUnits;
120     }
121 
122     /** Sets autoscroll scroll units.
123     * When autoscroll(..) method is called, it will scroll the
124     * component accordign to scroll unit in appropriate direction.
125     * So, scrollUnits.top says how much (in pixels) the component
126     * will autoscroll up etc...
127     */
128     public void setScrollUnits(Insets   scrollUnits) {
129         this.scrollUnits = scrollUnits;
130     }
131 
132     /** Getter for viewport of asociated component.
133     * Can return null if component is not contained in any viewport.
134     */
135     JViewport   getViewport() {
136         if (viewport == null) {
137             Component   curComp = comp;
138 
139             while (!(curComp instanceof JViewport  ) && (curComp != null)) {
140                 curComp = comp.getParent();
141             }
142 
143             viewport = (JViewport  ) curComp;
144         }
145 
146         return viewport;
147     }
148 }
149
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