Question

I what to draw a circle that uniformly fits into its space, with a constant a stoke thickness. A ViewBox gets me the uniform fit, but not the constant stoke thickness.

<Viewbox Stretch='Uniform' MinHeight='10' MinWidth='10' >     <Ellipse Height='10' Width='10' Fill='Red' StrokeThickness='1' Stroke='Yellow'/> </Viewbox> 

Answer 1

If you don’t specify a width or height of the ellipse, the default values will be ‘Auto’. Combined with the default HorizontalAlignment/VerticalAligment values of ‘Stretch’, this should cause the ellipse to ‘stretch’ to the width and height of its container (with constant stroke thickness).

The *ContentAlignment properties of the parent container may affect this behavior, but again, the default, unset values should give you the behavior you want.

Edit: revising my suggestion because I did not realized the ellipse must remain a circle (don’t worry, I’ve decided to pick up a copy of ‘Reading for Comprehension’).

I suggest you bind the width and height properties of the ellipse to a MultiBinding of the parent container’s ActualWidth and ActualHeight properties. Then implement a ‘multi-value converter’ that will return the minimum value from the multi-binding.

So the converter might look like this:

class MinimumValueConverter : IMultiValueConverter {     public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)     {         return values.Cast<double>().Min();     }      public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)     {         throw new NotImplementedException();     } } 

And the ellipse properties could be bound like this:

<Window.Resources>     <l:MinimumValueConverter x:Key='MinimumValueConverter' /> </Window.Resources> <Ellipse Stroke='Black' StrokeThickness='1'>     <Ellipse.Width>         <MultiBinding Converter='{StaticResource MinimumValueConverter}'>             <Binding RelativeSource='{RelativeSource FindAncestor, AncestorType={x:Type UIElement}}' Path='ActualWidth' />             <Binding RelativeSource='{RelativeSource FindAncestor, AncestorType={x:Type UIElement}}' Path='ActualHeight' />         </MultiBinding>     </Ellipse.Width>     <Ellipse.Height>         <MultiBinding Converter='{StaticResource MinimumValueConverter}'>             <Binding RelativeSource='{RelativeSource FindAncestor, AncestorType={x:Type UIElement}}' Path='ActualWidth' />             <Binding RelativeSource='{RelativeSource FindAncestor, AncestorType={x:Type UIElement}}' Path='ActualHeight' />         </MultiBinding>     </Ellipse.Height> </Ellipse>