Position a triangle along a slider - wpf

Question

I want to extend a slider by a triangle pointing to a fixed position (the triangle will not be moved like the thumb).
The current code draws the triangle at position 0,0.
<Path Data="M 0 0 L 6 0 L 3 7 Z" Stroke="Black" Fill="Black"/>
The result looks like this:
In this example the slider represents a % value (the range is not necessarily 0 - 100). The triangle should be positioned at a fixed % value, which is provided via dependency property.
My question is: how do I relocate the triangle to point to that % value (not the thumbs value)?

Answer 1

With fixed ratio it would look like:
<Grid>
<Grid Margin="0,-10,0,0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="25*"/>
<ColumnDefinition Width="0"/>
<ColumnDefinition Width="75*"/>
</Grid.ColumnDefinitions>
<Canvas Grid.Column="1">
<Path Data="M -3 0 L 3 0 L 0 7 Z" Stroke="Black" Fill="Black"/>
</Canvas>
</Grid>
<Slider/>
</Grid>
Notice that I changed the path to center it on the canvas.
To make the ratio dynamic you need a converter to be able to bind it to a property (a double named Percent here)
<Window.Resources>
<local:GridLengthPercentConverter x:Key="GridLengthPercentConverter" />
</Window.Resources>
...
<Grid>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="{Binding
Path=Percent,
Converter={StaticResource GridLengthPercentConverter},
ConverterParameter=first"/>
<ColumnDefinition Width="0"/>
<ColumnDefinition Width="{Binding
Path=Percent,
Converter={StaticResource GridLengthPercentConverter},
ConverterParameter=other"/>
</Grid.ColumnDefinitions>
<Canvas Grid.Column="1">
<Path Data="M -3 0 L 3 0 L 0 7 Z" Stroke="Black" Fill="Black"/>
</Canvas>
</Grid>
<Slider/>
</Grid>
Here's how the converter looks like:
public class GridLengthPercentConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if(parameter.ToString() == "first")
return new GridLength((double)value, GridUnitType.Star)
return new GridLength(100 - (double)value, GridUnitType.Star)
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return null;
}
}