Styling Visual States

Question

I am using the VisualStateManager from the WPF Toolkit. I've created a custom control, part of a reusable controls library, with numerous visual states. Now I want to allow the client of my library to easily restyle the fonts and colors of these visual states. What's the standard way of doing this? Must I require the client to replace the entire control template and replace all the visual states, even if they're only interested in modifying just one? Or is there a better way... like how could I make GoToState defer to a client-supplied trigger intended to override a visual state's default font and color? Other ideas?

Answer 1

I got this working for the first case I tried. The goal was to make it so that this code would have an effect:

  <l:MyControl>
    <l:MyControl.MyStateStyle>
      <Style>
        <Setter Property="Control.Background" Value="LightBlue"/>
        <Setter Property="TextElement.Foreground" Value="White"/>
        <Setter Property="TextElement.FontStyle" Value="Italic"/>
      </Style>
    </l:MyControl.MyStateStyle> </l:MyControl>

This is how I did it:

Style style = new Style();

if ( MyState == MyState.State1Normal )
    VisualStates.GoToState( this, useTransitions, State1Normal );
else if ( MyState == MyState.State2 ) {
    if ( Owner.State2Style != null )
        style = style.Merge( Owner.State2Style );
    else
        VisualStates.GoToState( this, useTransitions, State2 );
} else if ( MyState == MyState.State3 ) {
    if ( Owner.State3Style != null )
        style = style.Merge( Owner.State3Style );
    else
        VisualStates.GoToState( this, useTransitions, State3 );
}

Style = style;

Notice the Style.Merge extension method. I got it from http://bea.stollnitz.com/blog/?p=384 . It enables me to combine the effects of multiple visual state groups.