Move window when flyout is open

[hercmaroudas]

When a flyout was open you weren't able to move the window where the flyout was over the title bar. This was particularly anoying if you wished to move the window while a flyout was opened as a modal flyout or covered the entire area of the window.

I've implemented a change that enables the window to be moved when a flyout is opened and the mouse cursor is within the windows title bar area.

If the default behaviour was intended by design perhaps this feature could be optional with a property.

I hope this is ok.

[punker76]

this should be also called in FlyoutsControl to avoid memory leaks (cause it's possible to have dynamic flyouts)

        protected override void ClearContainerForItemOverride(DependencyObject element, object item)
        {
            var window = this.TryFindParent<MetroWindow>();
            if (window != null)
            {
                ((Flyout)element).ClearParentWindowEvents(window);
            }
            base.ClearContainerForItemOverride(element, item);
        }

[hercmaroudas]

Ok thanks Punker, added and sent the pull request.

[punker76]

@hercmaroudas looks good, i'll be add this to 1.2.0

[hercmaroudas]

Thanks @punker76 👍

[thoemmi]

Looks ok, though I don't like that Flyout accesses MetroWindow directly, but I have no better idea.

However, I would suggest some changes to your Flyout.xaml: In your PR you move the flyout's content down by the height of the titlebar. I'd prefer to keep the content where it is but overlay it with the PART_WindowTitle. So I'd remove the RowDefinitions again, add the Rectangle after the AdornerDecorator, and set its VerticalAlignment to Top:

    <AdornerDecorator>
        <!-- -->
    </AdornerDecorator>
    <Rectangle x:Name="PART_WindowTitle"
               Height="{Binding TitlebarHeight, Mode=OneWay, RelativeSource={RelativeSource FindAncestor, AncestorLevel=1, AncestorType={x:Type Controls:MetroWindow}}}"
               HorizontalAlignment="Stretch" VerticalAlignment="Top"
               StrokeThickness="0"
               Fill="Transparent"/>