MenuScrollingVisibilityConverter Class

Definition

Namespace:

System.Windows.Controls

Assembly:

PresentationFramework.dll

Represents a data-binding converter to handle the visibility of repeat buttons in scrolling menus.

public ref class MenuScrollingVisibilityConverter sealed : System::Windows::Data::IMultiValueConverter

public sealed class MenuScrollingVisibilityConverter : System.Windows.Data.IMultiValueConverter

type MenuScrollingVisibilityConverter = class
    interface IMultiValueConverter

Public NotInheritable Class MenuScrollingVisibilityConverter
Implements IMultiValueConverter

Inheritance

Object

MenuScrollingVisibilityConverter

Implements

IMultiValueConverter

Examples

The following example uses the MenuScrollingVisibilityConverter in the ControlTemplate of a ScrollViewer for a menu.

For a complete sample, see Styling with ControlTemplates Sample.

<!--ScrollViewer for a MenuItem-->
<MenuScrollingVisibilityConverter x:Key="MenuScrollingVisibilityConverter" />

<Style x:Key="MenuScrollViewer"
       TargetType="{x:Type ScrollViewer}"
       BasedOn="{x:Null}">
  <Setter Property="HorizontalScrollBarVisibility"
          Value="Hidden" />
  <Setter Property="VerticalScrollBarVisibility"
          Value="Auto" />
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="{x:Type ScrollViewer}">
        <Grid SnapsToDevicePixels="True">
          <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
          </Grid.ColumnDefinitions>
          <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
            <RowDefinition Height="Auto" />
          </Grid.RowDefinitions>
          <Border Grid.Row="1"
                  Grid.Column="0">
            <ScrollContentPresenter Margin="{TemplateBinding Padding}" />
          </Border>
          <RepeatButton Style="{StaticResource MenuScrollButton}"
                        Grid.Row="0"
                        Grid.Column="0"
                        Command="{x:Static ScrollBar.LineUpCommand}"
                        CommandTarget="{Binding RelativeSource={RelativeSource TemplatedParent}}"
                        Focusable="False">
            <RepeatButton.Visibility>
              <MultiBinding FallbackValue="Visibility.Collapsed"
                            Converter="{StaticResource MenuScrollingVisibilityConverter}"
                            ConverterParameter="0">
                <Binding RelativeSource="{RelativeSource TemplatedParent}"
                         Path="ComputedVerticalScrollBarVisibility" />
                <Binding RelativeSource="{RelativeSource TemplatedParent}"
                         Path="VerticalOffset" />
                <Binding RelativeSource="{RelativeSource TemplatedParent}"
                         Path="ExtentHeight" />
                <Binding RelativeSource="{RelativeSource TemplatedParent}"
                         Path="ViewportHeight" />
              </MultiBinding>
            </RepeatButton.Visibility>
            <Path Fill="{DynamicResource {x:Static SystemColors.MenuTextBrushKey}}"
                  Data="{StaticResource UpArrow}" />
          </RepeatButton>
          <RepeatButton Style="{StaticResource MenuScrollButton}"
                        Grid.Row="2"
                        Grid.Column="0"
                        Command="{x:Static ScrollBar.LineDownCommand}"
                        CommandTarget="{Binding RelativeSource={RelativeSource TemplatedParent}}"
                        Focusable="False">
            <RepeatButton.Visibility>
              <MultiBinding FallbackValue="Visibility.Collapsed"
                            Converter="{StaticResource MenuScrollingVisibilityConverter}"
                            ConverterParameter="100">
                <Binding RelativeSource="{RelativeSource TemplatedParent}"
                         Path="ComputedVerticalScrollBarVisibility" />
                <Binding RelativeSource="{RelativeSource TemplatedParent}"
                         Path="VerticalOffset" />
                <Binding RelativeSource="{RelativeSource TemplatedParent}"
                         Path="ExtentHeight" />
                <Binding RelativeSource="{RelativeSource TemplatedParent}"
                         Path="ViewportHeight" />
              </MultiBinding>
            </RepeatButton.Visibility>
            <Path Fill="{DynamicResource {x:Static SystemColors.MenuTextBrushKey}}"
                  Data="{StaticResource DownArrow}" />
          </RepeatButton>
        </Grid>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

Remarks

The MenuScrollingVisibilityConverter determines whether a menu should display the repeat buttons when a menu has too many items to fit on the screen at once. Use the converter with a MultiBinding that has four bindings. The four bindings should be to properties of the parent ScrollViewer: If the menu items are organized vertically (which is the default for menus), bind to ComputedVerticalScrollBarVisibility, VerticalOffset, ExtentHeight, and ViewportHeight. If the menu items are organized horizontally, bind to ComputedHorizontalScrollBarVisibility, HorizontalOffset, ExtentWidth, and ViewportWidth.

Set MultiBinding.ConverterParameter to 0 or 100. The value is treated as a percentage and determines whether a button is hidden when the ScrollViewer is at the given location. When the ScrollViewer is at the top, the position of the ScrollViewer is 0% and the top button is hidden. When the ScrollViewer is at the bottom, the position of the ScrollViewer is 100% and the bottom button is hidden.

Constructors

MenuScrollingVisibilityConverter()

Initializes a new instance of the MenuScrollingVisibilityConverter class.

Methods

Convert(Object[], Type, Object, CultureInfo)	Called when moving a value from a source to a target.
ConvertBack(Object, Type[], Object, CultureInfo)	Not supported.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)