Accessibility/SoftFocus: Difference between revisions

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Revision as of 23:01, 30 November 2011

4,404 bytes added , 30 November 2011

→‎Presenting Virtual Cursor

Eeejay

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@@ Line 6: / Line 6: @@
 === nsIAccessiblePivot ===
+ typedef short nsAccessiblePivotBoundary;
   interface nsIAccessiblePivot : nsISupports
   {
+   const nsAccessiblePivotBoundary BOUNDARY_CHAR            = 0;
+   const nsAccessiblePivotBoundary BOUNDARY_WORD            = 1;
+   const nsAccessiblePivotBoundary BOUNDARY_LINE            = 2;
+   const nsAccessiblePivotBoundary BOUNDARY_ATTRIBUTE_RANGE = 3;
     /*
      * The accessible the pivot is currently pointed at.
@@ Line 51: / Line 58: @@
      */
     void setTextOffset(in long aStartOffset, in long aEndOffset);
+   /**
+    * Move pivot to next object via given traversal rule, which defines a filter
+    *  and a search order.
+    *
+    * @param aRule traversal rule to use.
+    * @param aLast traverse to the last occurance in the document.
+    * @return true on success, false if there are no new nodes to traverse to.
+    */
+   boolean nexObject(in nsIAccessibleTraversalRule aRule, in boolean aLast);
+   /**
+    * Move pivot to previous object via given traversal rule, which defines a
+    *  filter and a search order.
+    *
+    * @param aRule traversal rule to use.
+    * @param aFirst traverse to the first occurance in the document.
+    * @return true on success, false if there are no new nodes to traverse to.
+    */
+   boolean previousObject(in nsIAccessibleTraversalRule aRule, in boolean aFirst);
+   /**
+    * Move pivot to next text range.
+    *
+    * @param aBoundary type of boundary for next text range, character, word, etc.
+    * @param aLast traverse to the last occurance in the document.
+    * @return true on success, false if there are is no more text.
+    */
+   boolean nextText(in nsAccessiblePivotBoundary aBoundary, in boolean aLast);
+   /**
+    * Move pivot to previous text range.
+    *
+    * @param aBoundary type of boundary for previous text range, character, word,
+    *   etc.
+    * @param aFirst traverse to the first occurance in the document.
+    * @return true on success, false if there are is no more text.
+    */
+   boolean previousText(in nsAccessiblePivotBoundary aBoundary, in boolean aFirst);
     /*
@@ Line 92: / Line 138: @@
     readonly attribute nsIAccessiblePivot virtualCursor;
   }
+=== nsIAccessibleVirtualCursorChangeEvent ===
+An accessible event of  type EVENT_VIRTUALCURSOR_CHANGE. Fired when the virtual cursor's pivot is moved.
+ interface nsIAccessibleVirtualCursorChangeEvent: nsISupports
+ {
+   /**
+    * Document's virtual cursor pivot.
+    */
+   readonly attribute nsIAccessiblePivot pivot;
+   /**
+    * Previous object pointed at by virtual cursor. null if none.
+    */
+   readonly attribute nsIAccessible oldAccessible;
+   /**
+    * Previous start offset of pivot. -1 if none.
+    */
+   readonly attribute long oldStartOffset;
+   /**
+    * Previous end offset of pivot. -1 if none.
+    */
+   readonly attribute long oldEndOffset;
+ };
 == Example Usage ==
 === Setting Virtual Cursor ===
+A traversal rule that goes to headers.
+ var headerTraversalRule = {
+   QueryInterface: XPCOMUtils.generateQI([Ci.nsIAccessibleTraversalRule]),
+   acceptRoles: [Ci.nsIAccessibleRole.ROLE_HEADER],
+   acceptStates: 0xffffffff,
+   acceptExtStates: 0xffffffff,
+   skipStates: Ci.nsIAccessibleStates.STATE_INVISIBLE,
+   skipExtStates: Ci.nsIAccessibleStates.EXT_STATE_DEFUNCT,
+   traversalOrder: Ci.nsIAccessibleTraversalRule.ORDER_DEPTH_FIRST,
+   filterAccessible: function (aAccessible) {return Ci.nsIAccessibleTraversalRule.FILTER_ACCEPT;}
+ }
+A simple object traversal rule that goes to all leaves or focusable items.
+ var objectTraversalRule = {
+   QueryInterface: XPCOMUtils.generateQI([Ci.nsIAccessibleTraversalRule]),
+   acceptRoles: [],
+   acceptStates: 0xffffffff,
+   acceptExtStates: 0xffffffff,
+   skipStates: Ci.nsIAccessibleStates.STATE_INVISIBLE,
+   skipExtStates: Ci.nsIAccessibleStates.EXT_STATE_DEFUNCT,
+   traversalOrder: Ci.nsIAccessibleTraversalRule.ORDER_DEPTH_FIRST,
+   filterAccessible: function (aAccessible) {
+      if (this._isFocusable(aAccessible))
+        return Ci.nsIAccessibleTraversalRule.FILTER_ACCEPT;
+      if (this._isFocusable(aAccessible.parent))
+        return Ci.nsIAccessibleTraversalRule.FILTER_REJECT;
+      if (aAccessible.childCount == 0)
+        return Ci.nsIAccessibleTraversalRule.FILTER_ACCEPT;
+   },
+   _isFocusable: function (aAccessible) {
+     let state = {};
+     aAccessible.getState(state, null);
+     return state.value & Ci.nsIAccessibleStates.EXT_STATE_FOCUSABLE != 0;
+   }
+ }
 An input event handler that changes the virtual cursor.
   function inputEventHandler(event) {
-    ...
+    switch(event.keyCode) {
-    treeWalker.currentNode = docAcc.virtualCursor.accessible;
+   case 40:
-    if (treeWalker.next())
+     docAcc.virtualCursor.nextObject(objectTraversalRule, event.shiftKey);
-      docAcc.virtualCursor.setAccessible(treeWalker.currentNode);
+     break;
+    case 38:
+     docAcc.virtualCursor.previousObject(objectTraversalRule, event.shiftKey);
+     break;
+    case 39:
+     docAcc.virtualCursor.nextObject(headerTraversalRule, event.shiftKey);
+     break;
+   case 37:
+      docAcc.virtualCursor.previousObject(headerTraversalRule, event.shiftKey);
+     break;
+   default:
+     break;
   }
@@ Line 109: / Line 230: @@
   var VirtualCursorView = {
-    onPivotChanged: function onPivotChanged(aPivot, aOldAccessible, aOldStart, aOldEnd) {
+    handleEvent: function (aEvent) {
-      this.showRing(aPivot.accessible, aPivot.startOffset, aPivot.endOffset);
+     if (aEvent.type != Cu.nsIAccessibleEvent.EVENT_VIRTUALCURSOR_CHANGED)
+       return;
+     let event = aEvent.QueryInterface(Ci.nsIAccessibleVirtualCursorChangeEvent);
+      this.showRing(event.pivot.accessible, event.pivot.startOffset, event.pivot.endOffset);
     },
@@ Line 134: / Line 259: @@
       aAccessible.getBounds(x, y, w, h);
       drawRect(x.value, y.value, w.value, h.value);
-    },
+    }
-   QueryInterface: XPCOMUtils.generateQI([nsIAccessiblePivotObserver])
   }