CODEWITHSUNDEEP
wpfxamlmvvm
MoonKnight
MoonKnight

Reputation: 23833

Set Value on Property Value in Parent Style WPF

I have the following WPF Style for a custom control 

<Style TargetType="{x:Type local:TransportControl}">
    <Setter Property="MinorTickBrush" Value="{DynamicResource BlackBrush}"/>
    <Setter Property="MajorTickBrush" Value="{DynamicResource BlackBrush}"/>
    <Setter Property="IndicatorBrush" Value="{DynamicResource BlckBrush}"/>
    <Setter Property="ProgressBorderBrush" Value="{DynamicResource BlackBrush}"/>
    <Setter Property="ProgressBrush" Value="{DynamicResource HighlightBrush}"/>
    <Setter Property="IndicatorSize" Value="16"/>
    <Setter Property="IndicatorBrush" Value="{DynamicResource BlackBrush}"/>
    <Setter Property="IndicatorGlow" Value="True"/>
    <Setter Property="IndicatorGlowBrush" Value="GhostWhite"/>
    <Setter Property="FontFamily" Value="Segoe UI"/>

    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type local:TransportControl}">
                <Border Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}"
                        Padding="{Binding Path=DataContext.IndicatorSize, 
                            RelativeSource={RelativeSource AncestorType={x:Type local:TransportControl}}, 
                            Converter={StaticResource ValueToHorizontalPaddingConverter}}"
                        Margin="4,2">
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="20"/>
                            <RowDefinition Height="*"/>
                        </Grid.RowDefinitions>
                        <Canvas Name="PART_TimelineCanvas" Grid.Row="0" Height="20" ClipToBounds="False"/>
                        <Canvas Name="PART_ProgressCanvas" Grid.Row="1" ClipToBounds="False"/>
                        <Canvas Name="PART_IndicatorCanvas" 
                                  Grid.Row="0" 
                                  Grid.RowSpan="2" 
                                  ClipToBounds="False" 
                                  Panel.ZIndex="2"/>
                    </Grid>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

with the IValueConverter as 

public class ValueToHorizontalPaddingConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object format, CultureInfo culture)
    {
        double padding = System.Convert.ToDouble(value);
        return new Thickness(padding, 0, padding, 0);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

I am attempting to set the padding of the control so my indicator can be centered correctly. I want the padding of the control to be half the IndicatorSize set in the parent style. Currently, I am just trying to get it to be the IndicatorSize, but the binding I am attempting does not work as expected.

Padding="{Binding Path=DataContext.IndicatorSize, 
    RelativeSource={RelativeSource AncestorType={x:Type local:TransportControl}}, 
    Converter={StaticResource ValueToHorizontalPaddingConverter}}"

What am I doing wrong?

Thanks for your time.

Upvotes: 0

Views: 199

Answers (1)

Tobias Hoefer
Tobias Hoefer

Reputation: 1118

You can use TemplateBinding to do that:

Padding="{TemplateBinding IndicatorSize, Converter={StaticResource ValueToHorizontalPaddingConverter}}"

Another way of centering the indicator would be to give the border a name, get a reference to it in your custom control's OnApplyTemplate(..) method and set its Padding in C# whenever the IndicatorSize property changes. This way you would not need the binding and converter.

Upvotes: 1

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