UWP - SemanticZoom Header Height

I am currently implementing SemanticZoom for a Windows UWP app. As you may know, items will be grouped into different section (e.g. Group A, Group B, etc.)

The Group name will be the header.

I have changed the default style for SemanticZoom Group Header. Too bad I still can't figure out how to change the height of the header.

Screenshot:

The height of the header is too high for my taste

The Code for the custom SemanticZoom Style

  <Style TargetType="GridViewHeaderItem">
            <Setter Property="FontFamily" Value="Segoe UI" />
            <Setter Property="Background" Value="#ff00fe"/>
            <Setter Property="HorizontalContentAlignment" Value="Left" />
            <Setter Property="VerticalContentAlignment" Value="Top" />
            <Setter Property="Height" Value="10"/>
            <Setter Property="UseSystemFocusVisuals" Value="True" />
            <Setter Property="Margin" Value="0 10 10 0"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="GridViewHeaderItem">
                        <StackPanel Background="{TemplateBinding Background}"
              BorderBrush="{TemplateBinding BorderBrush}"
              BorderThickness="{TemplateBinding BorderThickness}">
                            <ContentPresenter x:Name="ContentPresenter"
                      Margin="{TemplateBinding Padding}"
                      Content="{TemplateBinding Content}"
                      ContentTemplate="{TemplateBinding ContentTemplate}"
                      ContentTransitions="{TemplateBinding ContentTransitions}"
                      HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                      VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
                        </StackPanel>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

XAML Code for the SemanticZoom

            <SemanticZoom >
            <SemanticZoom.ZoomedOutView>
                <GridView>
                    ...
                </GridView>
            </SemanticZoom.ZoomedOutView>
            <SemanticZoom.ZoomedInView>
                <GridView>
                    <GridView.ItemTemplate>
                        ....
                    </GridView.ItemTemplate>
                    <GridView.GroupStyle>
                        <GroupStyle>
                            <GroupStyle.HeaderTemplate>
                                <DataTemplate>
                                    <StackPanel Orientation="Vertical">
                                        <TextBlock Text='{Binding Key}' Foreground="Black" FontSize="38" />
                                    </StackPanel>
                                </DataTemplate>
                            </GroupStyle.HeaderTemplate>
                        </GroupStyle>
                    </GridView.GroupStyle>
                </GridView>
            </SemanticZoom.ZoomedInView>
        </SemanticZoom>

Looking forward to your help.

Solution

There's couple properties you should set for your custom template: MinHeight and Padding.

The default GridViewHeaderItem template can be found from C:\Program Files (x86)\Windows Kits\10\DesignTime\CommonConfiguration\Neutral\UAP\10.0.10240.0\Generic

From there you can find the things you should change:

Here's the full default style for GridViewHeaderItem.

<!-- Default style for Windows.UI.Xaml.Controls.GridViewHeaderItem -->
<Style TargetType="GridViewHeaderItem">
    <Setter Property="FontFamily" Value="{ThemeResource ContentControlThemeFontFamily}" />
    <Setter Property="FontSize" Value="{ThemeResource GridViewHeaderItemThemeFontSize}" />
    <Setter Property="Background" Value="Transparent" />
    <Setter Property="Margin" Value="0,0,0,4"/>
    <Setter Property="Padding" Value="12,8,12,0"/>
    <Setter Property="HorizontalContentAlignment" Value="Left" />
    <Setter Property="VerticalContentAlignment" Value="Top" />
    <Setter Property="MinHeight" Value="{ThemeResource GridViewHeaderItemMinHeight}"/>
    <Setter Property="UseSystemFocusVisuals" Value="True" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="GridViewHeaderItem">
                <StackPanel Background="{TemplateBinding Background}"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}">
                    <ContentPresenter x:Name="ContentPresenter"
                                      Margin="{TemplateBinding Padding}"
                                      Content="{TemplateBinding Content}"
                                      ContentTemplate="{TemplateBinding ContentTemplate}"
                                      ContentTransitions="{TemplateBinding ContentTransitions}"
                                      HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                                      VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
                    <Rectangle Stroke="{ThemeResource SystemControlForegroundBaseLowBrush}"
                               StrokeThickness="0.5"
                               Height="1"
                               VerticalAlignment="Bottom"
                               HorizontalAlignment="Stretch"
                               Margin="12,8,12,0"/>
                </StackPanel>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>