private void DetachFromVisualTree()
{
// remove the drag adorner
if (_dragAdorner != null)
AdornerLayer.GetAdornerLayer(this).Remove(_dragAdorner);
// remove the layout updated handler, if present
if (_contentPresenter != null)
{
_contentPresenter.LayoutUpdated -= ContentPresenterFirstArranged;
}
// remove the view finder display panel's visual brush and adorner
if (_viewFinderDisplay != null)
{
_viewFinderDisplay = null;
}
// set object references to null
_contentPresenter = null;
}
private void AttachToVisualTree()
{
// detach from the old tree
DetachFromVisualTree();
// create the drag adorner for selection operations
_dragAdorner = new DragAdorner(this);
// check the template for a SelectionBrush resource
if (Template.Resources.Contains("SelectionBrush"))
_dragAdorner.Brush = Template.Resources["SelectionBrush"] as Brush;
// check the template for a SelectionPen resource
if (Template.Resources.Contains("SelectionPen"))
_dragAdorner.Pen = Template.Resources["SelectionPen"] as Pen;
// check the template for key bindings
if (Template.Resources.Contains("InputBindings"))
{
InputBindingCollection inputBindings = Template.Resources["InputBindings"] as InputBindingCollection;
if (inputBindings != null)
{
InputBindings.AddRange(inputBindings);
}
}
// locate the content presenter
_contentPresenter =
VisualTreeHelperEx.FindDescendantByType(this, typeof(ContentPresenter)) as ContentPresenter;
if (_contentPresenter == null)
throw new InvalidTemplateException(ErrorMessages.GetMessage("ZoomboxTemplateNeedsContent"));
// check the template for an AdornerDecorator
AdornerLayer al = null;
AdornerDecorator ad =
VisualTreeHelperEx.FindDescendantByType(this, typeof(AdornerDecorator)) as AdornerDecorator;
if (ad != null)
{
al = ad.AdornerLayer;
}
else
{
// look for an inherited adorner layer
try
{
al = AdornerLayer.GetAdornerLayer(this);
}
catch (Exception)
{
}
}
// add the drag adorner to the adorner layer
if (al != null)
{
al.Add(_dragAdorner);
}
// TODO: Why is it necessary to walk the visual tree the first time through?
// If we don't do the following, the content is not laid out correctly (centered) initially.
VisualTreeHelperEx.FindDescendantWithPropertyValue(this, ButtonBase.IsPressedProperty, true);
// set a reference to the ViewFinder element, if present
SetValue(Zoombox.ViewFinderPropertyKey, Template.FindName("ViewFinder", this) as FrameworkElement);
// locate the view finder display panel
_viewFinderDisplay =
VisualTreeHelperEx.FindDescendantByType(this, typeof(ZoomboxViewFinderDisplay)) as
ZoomboxViewFinderDisplay;
// if a ViewFinder was specified but no display panel is present, throw an exception
if (ViewFinder != null && _viewFinderDisplay == null)
throw new InvalidTemplateException(ErrorMessages.GetMessage("ZoomboxHasViewFinderButNotDisplay"));
// set up the VisualBrush and adorner for the display panel
if (_viewFinderDisplay != null)
{
// create VisualBrush for the view finder display panel
CreateVisualBrushForViewFinder(_content);
// hook up event handlers for dragging and resizing the viewport
_viewFinderDisplay.MouseMove += new MouseEventHandler(ViewFinderDisplayMouseMove);
_viewFinderDisplay.MouseLeftButtonDown += new MouseButtonEventHandler(ViewFinderDisplayBeginCapture);
_viewFinderDisplay.MouseLeftButtonUp += new MouseButtonEventHandler(ViewFinderDisplayEndCapture);
// bind the ViewportRect property of the display to the Viewport of the Zoombox
Binding binding = new Binding("Viewport");
binding.Mode = BindingMode.OneWay;
binding.Converter = new ViewFinderSelectionConverter(this);
binding.Source = this;
_viewFinderDisplay.SetBinding(ZoomboxViewFinderDisplay.ViewportRectProperty, binding);
}
// set up event handler to run once the content presenter has been arranged
_contentPresenter.LayoutUpdated += ContentPresenterFirstArranged;
}
