private static void OnHasGalleryChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
d.CoerceValue(CanUserResizeHorizontallyProperty);
d.CoerceValue(CanUserResizeVerticallyProperty);
d.CoerceValue(DropDownHeightProperty);
RibbonMenuButton menuButton = (RibbonMenuButton)d;
if (menuButton.IsDropDownOpen)
{
// First time the dropdown opens, HasGallery is always false
// because item container generation never happened yet and hence
// it ignores DropDownHeight. Hence reuse DropDownHeight when HasGallery
// value changes.
RibbonHelper.SetDropDownHeight(menuButton._itemsPresenter, (bool)e.NewValue, menuButton.DropDownHeight);
}
// Note that when the HasGallery property changes we expect that the
// VerticalScrollBarVisibilityProperty for the primary _submenuScrollViewer
// that hosts galleries and/or menu items is updated. Even though this
// property is marked AffectsMeasure it doesn't exactly cause the additonal
// call to ScrollViewer.MeasureOverrider because HasGallery is typically
// updated during a Measure pass when PrepareContainerForItemOverride is
// called and thus the invalidation noops. To ensure that we call
// ScrollViewer.MeasureOverride another time after this property has been
// updated, we need to wait for the current Measure pass to subside and
// then InvalidateMeasure on the _submenuScrollViewer.
RibbonHelper.InvalidateScrollBarVisibility(menuButton._submenuScrollViewer);
}
