have FrameworkElement.ApplyTemplate call a CLR event after it has called OnApplyTemplate

[trebahl]

I often find a need to execute code after a template has been applied, for instance to slightly alter what has been generated by the default template, or just for debuging purposes. I make do by defining a derived class overriding OnApplyTemplate, but having an event to do the same thing would be more versatile.

A case where an event would be orders of magnitude more convenient: say the template of a control A generates a control B and I want to plug into B's OnApplyTemplate. I can't override B's OnApplyTemplate since I didn't call its constructor (and I don't want to copy-paste the whole xaml of A to modify it). The best workaround I have found is to plug into A's OnApplyTemplate (which I can control because I am creating A from code), extract B and call its ApplyTemplate immediately, then apply the tweak and pray it doesn't get undone later.

[lindexi]

@trebahl How about show your ideas code?

[trebahl]

Err, I'm not sure which code you mean. The latest case where I needed this was to create an intermediate size between RibbonImageSize.Large and Small for System.Windows.Controls.Ribbon.RibbonButton and RibbonMenuButton with the image being 24*24 while still having the text to the right of the image. I did it by setting ImageSize to RibbonImageSize.Small, and enlarging the sizes after the template is applied.

I ended up overriding both classes' OnApplyTemplate to have them call this code:

                var ctrl = elt;  // elt = the top level button
                foreach (var ip in imagepath)   // for RibbonMenuButton, imagepath = [ "PART_ToggleButton", "PART_Image" ]; for RibbonButton it's only [ "PART_Image" ]
                {
                    ctrl = ctrl.GetTemplateChild(ip) as FrameworkElement;
                    if (ctrl != elt) ctrl.ApplyTemplate();  // create the template immediately so we can find the image inside; required for RibbonMenuButton as it contains a togglebutton that contains the image in its template
                }
                while (ctrl != null) // move back up the tree to increase the sizes
                {
                    if (!double.IsNaN(ctrl.Width)) ctrl.Width += MEDIUM_INCREMENT;
                    if (!double.IsNaN(ctrl.Height)) ctrl.Height += MEDIUM_INCREMENT;
                    if (ctrl.MinWidth != 0) ctrl.MinWidth += MEDIUM_INCREMENT;
                    if (ctrl == elt) break;
                    ctrl = VisualTreeHelper.GetParent(ctrl) as FrameworkElement;
                }

With an event, I could plug the same event handler for all classes instead of having to define N derived classes, and instead of explicitly calling a child's applytemplate I could just plug a handler into its own event.

class ImageEnlarger
{
    string[] imagepath;
    public ImageEnlarger(FrameworkElement elt, params string[] imagepath)
    {
        this.imagepath = imagepath;
        Recurse(elt, 0);
    }
    void Recurse(FrameworkElement elt, int i)
    {
        elt.TemplateApplied += (o, e) =>
        {
            var next = current.GetTemplateChild(imagepath[i]);
            if (i + 1 == imagepath.Length)
            {
            // same code as above to move back up the tree
            }
            else
            {
                Recurse(next, i + 1);
            }
         }
     }
}

[lindexi]

It sounds like an interesting implementation method.