WPF global font size

Question

I\'m creating a WPF app and I would like to know the best way to be able to change the font size for every element in the ui. Do I create a resource dictionary and set Style

Answer 1

Application.Current.MainWindow.FontSize = _appBodyFontSize;

This way you can change the Font Size at run time also.

Answer 2

Using Resources in XAML is the way to go. Although there are many great answers to this question, I would like to add my two cents to the SCOPE of the Resource.

For Global accessibility in all of the Windows and User Controls of the Project, you can have your resource in the App.xaml file

<Application.Resources>
    <Style TargetType="{x:Type Control}" x:Key="GlobalFontSize">
        <Setter Property="FontSize" Value="28"/>
    </Style>
</Application.Resources>

For accessibility at a Window level, you can have your resource in your xaml file for Window

<Window.Resources>
    <Style TargetType="{x:Type Control}" x:Key="GlobalFontSize">
        <Setter Property="FontSize" Value="28"/>
    </Style>
</Window.Resources>

You could even have it at a Control level, for example

<DockPanel.Resources>
    <Style TargetType="{x:Type Control}" x:Key="GlobalFontSize">
        <Setter Property="FontSize" Value="28"/>
    </Style>
</DockPanel.Resources>

Answer 3

If you need to programmatically change global FontSize, not statically (XAML), to be applied once for all your windows, you can do:

TextElement.FontSizeProperty.OverrideMetadata(
            typeof(TextElement),
            new FrameworkPropertyMetadata(16.0));

        TextBlock.FontSizeProperty.OverrideMetadata(
            typeof(TextBlock),
            new FrameworkPropertyMetadata(16.0));

This values are applied to any TextBlock, Labels and almost any text in any windows, whereas it has not a explicit FontSize defined. But this does not affect for TextBox, you have to write a similar code for it or any other special controls.

Answer 4

TextElement.FontSize is an inherit property, which means you can simply set the font size at root element, and all the children elements will use that size (as long as you don't change them manually)

Answer 5

FontSizeProperty is inherited from Parent Control. So you just need to change FontSize of your main window.

If you don't need dynamic behaviour this should work:

Add a style for Window to your ResourceDictionary

<Style TargetType="{x:Type Window}">
     <Setter Property="FontSize" Value="15" />
</Style>

Apply the style to your main form (will not be applied implicit because its a derived type)

 Style = (Style)FindResource(typeof (Window));

Answer 6

To dynamically change the font size globally with ctrl-mousewheel:

XAML:

<Window Name="MainWindow" ... PreviewMouseWheel="MainWindow_PreviewMouseWheel">

code behind:

private void MainWindow_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
{
    if ((Keyboard.Modifiers & ModifierKeys.Control) != 0)
    {
        if (e.Delta > 0)
            ++mainCtrl.FontSize;
        if (e.Delta < 0 && mainCtrl.FontSize > 1)
             --mainCtrl.FontSize;
    }
}