internal bool ValidateTabKeyHandleIsWithin( FrameworkElement originalSource, KeyboardDevice keyboardDevice )
{
DependencyObject predictedNextVisual = null;
//If the original source is not a control (e.g. the cells panel instead of a cell), columns will be used to move focus.
//In the case of a ListBox set with Cycle or Contained navigation mode, we must move in the other direction if on the first or last item,
//since PedictFocus will throw is we use FocusNavigationDirection.First/Last.
if( originalSource != null )
{
if( ( keyboardDevice.Modifiers & ModifierKeys.Shift ) == ModifierKeys.Shift )
{
predictedNextVisual = originalSource.PredictFocus( FocusNavigationDirection.Left );
if( predictedNextVisual == null )
{
predictedNextVisual = originalSource.PredictFocus( FocusNavigationDirection.Up );
if( predictedNextVisual == null )
{
KeyboardNavigationMode navigationMode = ( KeyboardNavigationMode )originalSource.GetValue( KeyboardNavigation.TabNavigationProperty );
if( navigationMode == KeyboardNavigationMode.Cycle || navigationMode == KeyboardNavigationMode.Contained )
{
predictedNextVisual = originalSource.PredictFocus( FocusNavigationDirection.Right );
if( predictedNextVisual == null )
{
predictedNextVisual = originalSource.PredictFocus( FocusNavigationDirection.Down );
}
}
}
}
}
else
{
predictedNextVisual = originalSource.PredictFocus( FocusNavigationDirection.Right );
if( predictedNextVisual == null )
{
predictedNextVisual = originalSource.PredictFocus( FocusNavigationDirection.Down );
if( predictedNextVisual == null )
{
KeyboardNavigationMode navigationMode = ( KeyboardNavigationMode )originalSource.GetValue( KeyboardNavigation.TabNavigationProperty );
if( navigationMode == KeyboardNavigationMode.Cycle || navigationMode == KeyboardNavigationMode.Contained )
{
predictedNextVisual = originalSource.PredictFocus( FocusNavigationDirection.Left );
if( predictedNextVisual == null )
{
predictedNextVisual = originalSource.PredictFocus( FocusNavigationDirection.Up );
}
}
}
}
}
}
if( predictedNextVisual != null )
{
Cell ownerCell = Cell.FindFromChild( predictedNextVisual );
if( ( ownerCell != null ) && ( ownerCell.ParentColumn == this.ParentDataGridControl.CurrentColumn ) )
{
if( object.Equals( ownerCell.ParentRow.DataContext, this.ParentDataGridControl.CurrentItemInEdition ) )
return true;
}
}
return false;
}
private static DependencyObject PredictNextElement( FrameworkElement source, KeyboardDevice device )
{
foreach( var direction in NavigationHelper.GetFocusNavigationDirections( source, device ) )
{
var target = source.PredictFocus( direction );
if( target != null )
return target;
}
return null;
}
