WPF derived Shape triggering redraw on property change

Question

I have a circular progress bar, which I have implemented as a class derived from Shape. I added DependencyProperties for all my properties that I need to bind. Property Value represents the progress. I overrided DefiningGeometry.

Now I want to get the progress bar to reflect to change when Value changes. My current approach is to register a PropertyChangedCallback on the DepencencyProperties that fires shape.InvalidateVisual().

This works fine, unless I have a Tooltip over my progress bar. A Timer increments Value, and the the Tooltip flickers once.

What would be the right way to get the shape updated?

Answer 1

It turned out that the flicker was triggered by an extended ObservableCollection that would would generate a NotifyCollectionChangedAction.Reset event that triggered a redraw of all items in the ItemsControl containing the Shapes.

Following How to properly refresh a custom shape in WPF? I improved my DepependecyProperty to:

    public static readonly DependencyProperty StartProperty =
        DependencyProperty.Register(
            "Start",
            typeof(double),
            typeof(CircleSegment),
            new FrameworkPropertyMetadata(
                0.0,
                FrameworkPropertyMetadataOptions.AffectsRender));

    /// <summary>
    /// Start of the Segment. 0 is top (12 o'clock), 0.25 is right (3 o'clock), 0.25 is bottom (6 o'clock), 0.75 is left (9 o'clock).
    /// Painting is always Clockwise from Start to End.
    /// </summary>
    [TypeConverter(typeof(LengthConverter))]
    public double Start
    {
        get { return (double)GetValue(StartProperty); }
        set { SetValue(StartProperty, value); }
    }