Based on the following code :
<GroupBox>
<GroupBox.Template>
<ControlTemplate TargetType="{x:Type GroupBox}">
<ContentPresenter TextElement.FontSize="28" />
</ControlTemplate>
</GroupBox.Template>
<TextBlock>Test</TextBlock>
</GroupBox>
I was expecting "Test" to be displayed with FontSize=28. But it uses the default size instead.
If I remove the TextBlock like this :
<GroupBox>
<GroupBox.Template>
<ControlTemplate TargetType="{x:Type GroupBox}">
<ContentPresenter TextElement.FontSize="28" />
</ControlTemplate>
</GroupBox.Template>
Test
</GroupBox>
The text is now the displayed with 28 as FontSize.
Shouldn't the property value be inherited when I use a TextBlock ?
This other question How do I Change the FontFamily on a ContentPresenter? doesn't help, as it works only for default content too.
This question also : How do I Change the FontFamily on a ContentPresenter?.
Both works whe you use the default content handler, but fails when you manually create a textblock.
Edit: As demonstrated in this other question, I've tried by simply using a ContentControl :
<StackPanel>
<StackPanel.Resources>
<ControlTemplate x:Key="UsingBorderTemplate" TargetType="{x:Type ContentControl}">
<Border BorderBrush="Red" BorderThickness="1" TextElement.FontFamily="Courier New" Margin="5">
<ContentPresenter/>
</Border>
</ControlTemplate>
<ControlTemplate x:Key="MyTemplate" TargetType="{x:Type ContentControl}">
<ContentPresenter TextElement.FontFamily="Courier New" Margin="5" />
</ControlTemplate>
</StackPanel.Resources>
<ContentControl Template="{StaticResource MyTemplate}">
I'm courier new!
</ContentControl>
<ContentControl Template="{StaticResource MyTemplate}">
<TextBlock>I'm default!</TextBlock>
</ContentControl>
</StackPanel>
You can change the template from "MyTemplate" to "UsingBorderTemplate" with the same result.