WindowButtonCommands is the group of three buttons at the right end of a MetroWindow's title bar: minimise, maximise/restore and close. Every MetroWindow has one, so you rarely place it yourself — but you may well want to hook or restyle it.

It derives from ContentControl and its template parts are PART_Min, PART_Max and PART_Close. The buttons drive WPF's own SystemCommands, so their behaviour is the platform's.

Cancelling a close

The one event, and the reason to reach for this control:

private void OnClosingWindow(object sender, ClosingWindowEventHandlerArgs args)
{
    args.Cancelled = !this.viewModel.CanClose;
}

<mah:MetroWindow.WindowButtonCommands>
    <mah:WindowButtonCommands ClosingWindow="OnClosingWindow" />
</mah:MetroWindow.WindowButtonCommands>

ClosingWindow is raised before SystemCommands.CloseWindow is called, and setting args.Cancelled stops it:

var args = new ClosingWindowEventHandlerArgs();
this.ClosingWindow?.Invoke(this, args);

if (args.Cancelled)
{
    return;
}

SystemCommands.CloseWindow(this.ParentWindow);

The tooltips come from Windows

All four are the buttons' tooltips, and all four default to null because the control fills them from the operating system:

if (string.IsNullOrWhiteSpace(this.Minimize))
{
    this.SetCurrentValue(MinimizeProperty, this.GetCaption(900));
}

GetCaption loads User32.dll and pulls string resources 900, 901, 903 and 905 out of it with LoadString. So the tooltips are Windows' own, already in the user's display language, and they are only worth setting if you want something other than the system wording.

Restore is the caption used while the window is maximised, when the middle button restores instead of maximising.

Styling the three buttons

Six properties, one per button per base colour:

Theme is a string holding a base-colour name and defaults to ThemeManager.BaseColorLight. Changing it swaps which set of three styles the buttons use — the same arrangement as WindowCommands and its LightTemplate / DarkTemplate pair.

That is six properties to set for one visual change, so in practice it is easier to restyle the buttons through the theme brushes, or to set the same style on both members of a pair when the title bar's base colour never changes.

ParentWindow is a read-only property pointing at the hosting MetroWindow.

Hiding them, and keeping them over flyouts

The window controls both, not this control:

<mah:MetroWindow ShowMinButton="False"
                 ShowMaxRestoreButton="False"
                 ShowCloseButton="False" />

WindowButtonCommandsOverlayBehavior decides whether the buttons stay visible above an open Flyout. It is an OverlayBehavior and defaults to Always, which is why the window buttons are drawn over the flyouts in the figures on the Flyouts page. A modal flyout still covers them.

Related

WindowCommands for your own buttons at either end of the title bar, MetroWindow for the window itself and the Show…Button properties, and Flyouts for the overlay behaviour.