[gui][PATCH] JComboBox - mouse drag events

[Olga Rodimina <rodimina at redhat dot com>]

Hi,

I've cleaned up changes from previous week that handle dragging events
in JComboBox. I will be committing this patch to java-gui-branch.

Olga.

Index: ChangeLog
===================================================================
RCS file: /cvs/gcc/gcc/libjava/ChangeLog,v
retrieving revision 1.2660.2.428
diff -u -r1.2660.2.428 ChangeLog
--- ChangeLog	28 Sep 2004 05:05:09 -0000	1.2660.2.428
+++ ChangeLog	28 Sep 2004 17:28:26 -0000
@@ -1,3 +1,16 @@
+2004-09-28   Olga Rodimina  <rodimina@redhat.com>
+
+	* javax/swing/plaf/basic/BasicComboPopup.java:
+	Added javadocs for undocumented fields.
+	(show): scroll down to the selected item and 
+	highlight selected item.
+	(startAutoScrolling): Implemented.
+	(stopAutoScrolling): Implemented.
+	(autoScrollUp): Implemented.
+	(autoScrollDown): Implemented.
+	(InvocationMouseHandler.mouseReleased): Implemented.
+	(InvocationMouseMotionHandler.mouseDragged): Implemented.
+
 2004-09-28  Jerry Quinn  <jlquinn@optonline.net>
 
 	* java/awt/image/RescaleOp.java: Implement.
Index: javax/swing/plaf/basic/BasicComboPopup.java
===================================================================
RCS file: /cvs/gcc/gcc/libjava/javax/swing/plaf/basic/BasicComboPopup.java,v
retrieving revision 1.1.2.2
diff -u -r1.1.2.2 BasicComboPopup.java
--- javax/swing/plaf/basic/BasicComboPopup.java	14 Sep 2004 19:47:54 -0000	1.1.2.2
+++ javax/swing/plaf/basic/BasicComboPopup.java	28 Sep 2004 17:28:27 -0000
@@ -39,6 +39,7 @@
 
 import java.awt.Component;
 import java.awt.Dimension;
+import java.awt.Point;
 import java.awt.Rectangle;
 import java.awt.event.ItemEvent;
 import java.awt.event.ItemListener;
@@ -58,10 +59,12 @@
 import javax.swing.JLabel;
 import javax.swing.JList;
 import javax.swing.JPopupMenu;
+import javax.swing.JScrollBar;
 import javax.swing.JScrollPane;
 import javax.swing.ListCellRenderer;
 import javax.swing.ListSelectionModel;
 import javax.swing.SwingConstants;
+import javax.swing.SwingUtilities;
 import javax.swing.Timer;
 import javax.swing.event.ListDataEvent;
 import javax.swing.event.ListDataListener;
@@ -78,37 +81,32 @@
  */
 public class BasicComboPopup extends JPopupMenu implements ComboPopup
 {
+  /* Timer for autoscrolling */
   protected Timer autoscrollTimer;
 
-  /**
-   * ComboBox associated with this popup
-   */
+  /** ComboBox associated with this popup */
   protected JComboBox comboBox;
 
-  /*
-   * FIXME: Document fields below
-   */
+  /** FIXME: Need to document */
   protected boolean hasEntered;
-  protected boolean isAutoScrolling;
 
   /**
-   * ItemListener listening to the selection changes in the combo box
+   * Indicates whether the scroll bar located in popup menu with comboBox's
+   * list of items is currently autoscrolling. This happens when mouse event
+   * originated in the combo box and is dragged outside of its bounds
    */
+  protected boolean isAutoScrolling;
+
+  /** ItemListener listening to the selection changes in the combo box */
   protected ItemListener itemListener;
 
-  /**
-   * This listener is not used
-   */
+  /** This listener is not used */
   protected KeyListener keyListener;
 
-  /**
-   * JList which is used to display item is the combo box
-   */
+  /** JList which is used to display item is the combo box */
   protected JList list;
 
-  /**
-   * This listener is not used
-   */
+  /** This listener is not used */
   protected ListDataListener listDataListener;
 
   /**
@@ -123,14 +121,10 @@
    */
   protected MouseMotionListener listMouseMotionListener;
 
-  /**
-   * This listener is not used
-   */
+  /** This listener is not used */
   protected ListSelectionListener listSelectionListener;
 
-  /**
-   * MouseListener listening to mouse events occuring in the combo box
-   */
+  /** MouseListener listening to mouse events occuring in the combo box */
   protected MouseListener mouseListener;
 
   /**
@@ -145,21 +139,19 @@
    */
   protected PropertyChangeListener propertyChangeListener;
 
-  /*
-   * FIXME: Document fields below
-   */
+  /** direction for scrolling down list of combo box's items */
   protected static int SCROLL_DOWN = 1;
+
+  /** direction for scrolling up list of combo box's items */
   protected static int SCROLL_UP = 0;
+
+  /** Indicates auto scrolling direction */
   protected int scrollDirection;
 
-  /**
-   * JScrollPane that contains list portion of the combo box
-   */
+  /** JScrollPane that contains list portion of the combo box */
   protected JScrollPane scroller;
 
-  /**
-   * This field is not used
-   */
+  /** This field is not used */
   protected boolean valueIsAdjusting;
 
   /**
@@ -184,13 +176,21 @@
 
     // popup should have same width as the comboBox and should be hight anough
     // to display number of rows equal to 'maximumRowCount' property
-    int popupHeight = getPopupHeightForRowCount(comboBox.getMaximumRowCount())
-                      + 4;
+    int popupHeight = getPopupHeightForRowCount(comboBox.getMaximumRowCount());
 
-    // FIXME: Uncomment this out once preferred size of JList will be working
-    // list.setPreferredSize(new Dimension(cbBounds.width, popupHeight));
+    list.setPreferredSize(new Dimension(cbBounds.width, popupHeight));
     super.setPopupSize(cbBounds.width, popupHeight);
 
+    // Highlight selected item in the combo box's drop down list
+    if (comboBox.getSelectedIndex() != -1)
+      list.setSelectedIndex(comboBox.getSelectedIndex());
+
+    //scroll scrollbar s.t. selected item is visible
+    JScrollBar scrollbar = scroller.getVerticalScrollBar();
+    int selectedIndex = comboBox.getSelectedIndex();
+    if (selectedIndex > comboBox.getMaximumRowCount())
+      scrollbar.setValue(getPopupHeightForRowCount(selectedIndex));
+
     // location specified is relative to comboBox
     super.show(comboBox, 0, cbBounds.height);
   }
@@ -557,37 +557,68 @@
   }
 
   /**
-   * DOCUMENT ME!
+   * This method start scrolling combo box's list of items  either up or down
+   * depending on the specified 'direction'
    *
-   * @param direction DOCUMENT ME!
+   * @param direction of the scrolling.
    */
   protected void startAutoScrolling(int direction)
   {
-    // FIXME: Need to implement
+    // FIXME: add timer
+    isAutoScrolling = true;
+
+    if (direction == SCROLL_UP)
+      autoScrollUp();
+    else
+      autoScrollDown();
   }
 
   /**
-   * DOCUMENT ME!
+   * This method stops scrolling the combo box's list of items
    */
   protected void stopAutoScrolling()
   {
-    // FIXME: Need to implement
+    // FIXME: add timer
+    isAutoScrolling = false;
   }
 
   /**
-   * DOCUMENT ME!
+   * This method scrolls up list of combo box's items up and highlights that
+   * just became visible.
    */
   protected void autoScrollUp()
   {
-    // FIXME: Need to implement
+    // scroll up the scroll bar to make the item above visible    
+    JScrollBar scrollbar = scroller.getVerticalScrollBar();
+    int scrollToNext = list.getScrollableUnitIncrement(super.getBounds(),
+                                                       SwingConstants.VERTICAL,
+                                                       SCROLL_UP);
+
+    scrollbar.setValue(scrollbar.getValue() - scrollToNext);
+
+    // If we haven't reached the begging of the combo box's list of items, 
+    // then highlight next element above currently highlighted element	
+    if (list.getSelectedIndex() != 0)
+      list.setSelectedIndex(list.getSelectedIndex() - 1);
   }
 
   /**
-   * DOCUMENT ME!
+   * This method scrolls down list of combo box's and highlights item in the
+   * list that just became visible.
    */
   protected void autoScrollDown()
   {
-    // FIXME: Need to implement
+    // scroll scrollbar down to make next item visible    
+    JScrollBar scrollbar = scroller.getVerticalScrollBar();
+    int scrollToNext = list.getScrollableUnitIncrement(super.getBounds(),
+                                                       SwingConstants.VERTICAL,
+                                                       SCROLL_DOWN);
+    scrollbar.setValue(scrollbar.getValue() + scrollToNext);
+
+    // If we haven't reached the end of the combo box's list of items
+    // then highlight next element below currently highlighted element
+    if (list.getSelectedIndex() + 1 != comboBox.getItemCount())
+      list.setSelectedIndex(list.getSelectedIndex() + 1);
   }
 
   /**
@@ -717,15 +748,36 @@
     }
 
     /**
-     * This method is invoked whenever mouse is released
+     * This method is invoked whenever mouse event was originated in the combo
+     * box and released either in the combBox list of items or in the combo
+     * box itself.
      *
      * @param e MouseEvent that should be handled
      */
     public void mouseReleased(MouseEvent e)
     {
-      // FIXME: should handle dragging events here, if
-      // mouse was dragged and released over the list of combobox's items,
-      // then item over which it was released should be selected.
+      // Get component over which mouse was released
+      Component src = (Component) e.getSource();
+      int x = e.getX();
+      int y = e.getY();
+      Component releasedComponent = SwingUtilities.getDeepestComponentAt(src,
+                                                                         x, y);
+
+      // if mouse was released inside the bounds of combo box then do nothing,
+      // Otherwise if mouse was released inside the list of combo box items
+      // then change selection and close popup
+      if (! (releasedComponent instanceof JComboBox))
+        {
+	  // List model contains the item over which mouse is released,
+	  // since it is updated every time the mouse is moved over a different
+	  // item in the list. Now that the mouse is released we need to
+	  // update model of the combo box as well. 	  
+	  comboBox.setSelectedIndex(list.getSelectedIndex());
+
+	  if (isAutoScrolling)
+	    stopAutoScrolling();
+	  hide();
+        }
     }
   }
 
@@ -742,13 +794,70 @@
     {
     }
 
+    /**
+     * This method is responsible for highlighting item in the drop down list
+     * over which the mouse is currently being dragged.
+     */
     public void mouseDragged(MouseEvent e)
     {
+      // convert point of the drag event relative to combo box list component
+      // figure out over which list cell the mouse is currently being dragged
+      // and highlight the cell. The list model is changed but the change has 
+      // no effect on combo box's data model. The list model is changed so 
+      // that the appropriate item would be highlighted in the combo box's 
+      // list.
+      if (BasicComboPopup.this.isVisible())
+        {
+	  int cbHeight = (int) comboBox.getPreferredSize().getHeight();
+	  int popupHeight = BasicComboPopup.this.getSize().height;
+
+	  // if mouse is dragged inside the the combo box's items list.
+	  if (e.getY() > cbHeight && ! (e.getY() - cbHeight >= popupHeight))
+	    {
+	      int index = list.locationToIndex(new Point(e.getX(),
+	                                                 (int) (e.getY()
+	                                                 - cbHeight)));
+
+	      int firstVisibleIndex = list.getFirstVisibleIndex();
+
+	      // list.locationToIndex returns item's index that would
+	      // be located at the specified point if the first item that
+	      // is visible is item 0. However in the JComboBox it is not 
+	      // necessarily the case since list is contained in the 
+	      // JScrollPane so we need to adjust the index returned. 
+	      if (firstVisibleIndex != 0)
+		// FIXME: adjusted index here is off by one. I am adding one
+		// here to compensate for that. This should be
+		// index += firstVisibleIndex. Remove +1 once the bug is fixed.
+		index += firstVisibleIndex + 1;
+
+	      list.setSelectedIndex(index);
+	    }
+	  else
+	    {
+	      // if mouse is being dragged at the bottom of combo box's list 
+	      // of items or at the very top then scroll the list in the 
+	      // desired direction.
+	      boolean movingUP = e.getY() < cbHeight;
+	      boolean movingDown = e.getY() > cbHeight;
+
+	      if (movingUP)
+	        {
+		  scrollDirection = SCROLL_UP;
+		  startAutoScrolling(SCROLL_UP);
+	        }
+	      else if (movingDown)
+	        {
+		  scrollDirection = SCROLL_DOWN;
+		  startAutoScrolling(SCROLL_DOWN);
+	        }
+	    }
+        }
     }
   }
 
   /**
-   * ItemHandler is an item listener that listens to selection event occuring
+   * ItemHandler is an item listener that listens to selection events occuring
    * in the combo box. FIXME: should specify here what it does when item is
    * selected or deselected in the combo box list.
    */