How to bind custom dependency property in control template? - wpf

Question

I have one class ChromeWindow which is derived from Window class. It has one custom dependency property
public class ChromeWindow : System.Windows.Window
{
public static readonly DependencyProperty TitleBarHeightProperty = DependencyProperty.Register("TitleBarHeight", typeof(int), typeof(ChromeWindow), new FrameworkPropertyMetadata(TitleBarHeightChangedCallback));
public int TitleBarHeight
{
get
{
return (int)GetValue(TitleBarHeightProperty);
}
set
{
SetValue(TitleBarHeightProperty, value);
}
}
private static void TitleBarHeightChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
}
}
And ChromeWindow has its own control template as below.
<ControlTemplate x:Key="ChromeWindowTemplate" TargetType="local:ChromeWindow">
<Grid>
<AdornerDecorator>
<ContentPresenter />
</AdornerDecorator>
<StackPanel x:Name="PART_TitleBar"
HorizontalAlignment="Stretch"
VerticalAlignment="Top"
Background="Transparent"
Height="?">
<StackPanel HorizontalAlignment="Right"
VerticalAlignment="Top"
Orientation="Horizontal">
<Button x:Name="PART_MinimizeButton"
Width="34"
Height="26"
Style="{DynamicResource SystemButton}"
ToolTip="Minimize">
<Path Width="8"
Height="8"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Data="F1M0,6L0,9 9,9 9,6 0,6z"
Fill="{Binding Foreground,
RelativeSource={RelativeSource Mode=FindAncestor,
AncestorType=Button}}" />
</Button>
<Button x:Name="PART_MaximizeButton"
Width="34"
Height="26"
Style="{DynamicResource SystemButton}"
ToolTip="Maximize">
<Path x:Name="PART_MaximizeButtonPath"
Width="10"
Height="10"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Data="F1M0,0L0,9 9,9 9,0 0,0 0,3 8,3 8,8 1,8 1,3z"
Fill="{Binding Foreground,
RelativeSource={RelativeSource Mode=FindAncestor,
AncestorType=Button}}" />
</Button>
<Button x:Name="PART_CloseButton"
Width="34"
Height="26"
Style="{DynamicResource SystemButton}"
ToolTip="Close">
<Path Width="10"
Height="8"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Data="F1M0,0L2,0 5,3 8,0 10,0 6,4 10,8 8,8 5,5 2,8 0,8 4,4 0,0z"
Fill="{Binding Foreground,
RelativeSource={RelativeSource Mode=FindAncestor,
AncestorType=Button}}" />
</Button>
</StackPanel>
</StackPanel>
<ResizeGrip x:Name="PART_ResizeGrip"
HorizontalAlignment="Right"
VerticalAlignment="Bottom"
Cursor="SizeNWSE"
Visibility="Hidden" />
</Grid>
</ControlTemplate>
How can I bind PART_Titlebar Height to custom dependency property called "TitleBarHeight" such that
If TitleBarHeight value is not specified, title bar height should
be calculated according to its child contents ?
If TitleBarHeight value is specified, use that value.
Thanks in advance.

Answer 1

The default value of the Height property is double.NaN, which indicates that there is no explicitly set height.
So you should change the type of your dependency property to double and set double.NaN as its default value:
public static readonly DependencyProperty TitleBarHeightProperty =
DependencyProperty.Register(
nameof(TitleBarHeight), typeof(double), typeof(ChromeWindow),
new FrameworkPropertyMetadata(double.NaN));
public double TitleBarHeight
{
get { return (double)GetValue(TitleBarHeightProperty); }
set { SetValue(TitleBarHeightProperty, value); }
}