/// <summary>
/// Overridden method which is called while a new child is being added to the collection.
/// Used to create thumb controls for each child, which is used to drag and resise the child.
/// </summary>
/// <param name="visualAdded">Item which got added</param>
/// <param name="visualRemoved">Item which got removed</param>
protected override void OnVisualChildrenChanged(DependencyObject visualAdded, DependencyObject visualRemoved)
{
VerticalDragThumb thumb = null;
Expander expander = visualRemoved as Expander;
if (expander != null)
{
expander.Collapsed -= new RoutedEventHandler(OnChildExpanderCollapsed);
}
expander = visualAdded as Expander;
if (expander != null)
{
expander.Collapsed += new RoutedEventHandler(OnChildExpanderCollapsed);
if (lastExpanderAdded != null)
{
// Create a thumb control and associate with this child
thumb = new VerticalDragThumb();
thumb.DragDelta += new DragDeltaEventHandler(OnThumbDragged);
this.Children.Insert(this.Children.Count - 1, thumb);
thumb.ExpanderAbove = lastExpanderAdded;
thumb.ExpanderBelow = expander;
base.OnVisualChildrenChanged(thumb, null);
}
lastExpanderAdded = expander;
}
base.OnVisualChildrenChanged(visualAdded, visualRemoved);
}
/// <summary>
/// Fired when user drags a thumb control to resise an expander
/// </summary>
private void OnThumbDragged(object sender, DragDeltaEventArgs e)
{
VerticalDragThumb thumb = sender as VerticalDragThumb;
Expander nextOpenExpanderAbove = GetNextExpander(thumb, true);
Expander nextOpenExpanderBelow = GetNextExpander(thumb, false);
bool movingUp = e.VerticalChange < 0;
// Check for moves which are not possible... or open or close expanders as needed to make the move...
if (e.VerticalChange == 0)
{
return;
}
if (movingUp && ((thumb.ExpanderAbove.IsExpanded == false && nextOpenExpanderAbove == null) || GetNextExpander(thumb, false, false) == null))
{
return;
}
if (!movingUp && ((thumb.ExpanderBelow.IsExpanded == false && nextOpenExpanderBelow == null) || GetNextExpander(thumb, false, false) == null))
{
return;
}
if (movingUp && thumb.ExpanderBelow != null && thumb.ExpanderBelow.IsExpanded == false)
{
thumb.ExpanderBelow.IsExpanded = true;
nextOpenExpanderBelow = thumb.ExpanderBelow;
}
if (!movingUp && nextOpenExpanderAbove == null)
{
thumb.ExpanderAbove.IsExpanded = true;
nextOpenExpanderAbove = thumb.ExpanderAbove;
}
// Handle the expander above
if (nextOpenExpanderAbove != null)
{
double currentHeight = (double)nextOpenExpanderAbove.GetValue(AllocatedSizeProperty);
double newHeight = currentHeight + e.VerticalChange;
if (newHeight > nextOpenExpanderAbove.MinHeight)
{
if (nextOpenExpanderAbove.IsExpanded == false)
{
nextOpenExpanderAbove.IsExpanded = true;
}
nextOpenExpanderAbove.SetValue(UserDefinedSizeProperty, newHeight);
}
else if (newHeight <= nextOpenExpanderAbove.MinHeight && nextOpenExpanderAbove.IsExpanded == true)
{
nextOpenExpanderAbove.IsExpanded = false;
nextOpenExpanderAbove.SetValue(UserDefinedSizeProperty, null);
}
}
// Handle the expander below
if (nextOpenExpanderBelow != null)
{
double currentHeight = (double)nextOpenExpanderBelow.GetValue(AllocatedSizeProperty);
double newHeight = currentHeight - e.VerticalChange;
if (newHeight > nextOpenExpanderBelow.MinHeight)
{
if (nextOpenExpanderBelow.IsExpanded == false)
{
nextOpenExpanderBelow.IsExpanded = true;
}
nextOpenExpanderBelow.SetValue(UserDefinedSizeProperty, newHeight);
}
else if (newHeight <= nextOpenExpanderBelow.MinHeight && nextOpenExpanderBelow.IsExpanded == true)
{
nextOpenExpanderBelow.IsExpanded = false;
nextOpenExpanderBelow.SetValue(UserDefinedSizeProperty, null);
}
if (thumb.ExpanderBelow != null && thumb.ExpanderBelow == lastExpanderAdded)
{
nextOpenExpanderBelow.SetValue(UserDefinedSizeProperty, null);
}
}
}