how to use a dynamicresource to set the scaletransform centerx and centrey

is this even possible? from what i have read about dynamic resources they
seem just what i need - if i understand it properly.

finding an example of who used one to achieve anything like this is however
a nightmare. my preumption is that i could refer to a property on an object
i defined in xaml - so i want the scametransform centerx to be the width of
the button / 2 and the centery to be the height of the button /2.

i have no idea how to acheive this. anyone know how or have i completly
missed the mark with what DynamicResources are?

cheers

Hi,

DynamicResources are not used for that kind of calculations. In order
to do what you want, you'll need a Binding, and a Converter:

First, make your CenterX and CenterY dependency properties (DP) bind
to their parent's Width and Height (in this case, a Button, 1 level
above):
<Button.RenderTransform>
<ScaleTransform
CenterX="{Binding Path=ActualWidth,Converter={StaticResource
DivideDoubleByTwoConverter},RelativeSource={RelativeSource
FindAncestor, GroupBox, 1}}"
CenterY="{Binding Path=ActualHeight,Converter={StaticResource
DivideDoubleByTwoConverter},RelativeSource={RelativeSource
FindAncestor, GroupBox, 1}}"/>
</Button.RenderTransform>

Note that the binding uses a Converter, which is a class implementing
IValueConverter. This class' sole use is to divide a double by two,
and return the result. Which in turn will be used in the binding:

[ValueConversion(typeof(double), typeof(double))]
public class DivideDoubleByTwoConverter: IValueConverter
{
public object Convert(object value, Type targetType, object
parameter, System.Globalization.CultureInfo culture)
{
if (targetType != typeof(double))
throw new InvalidOperationException("The target must
be a double");

double d = (double) value;
return ((double) d )/ 2;
}

public object ConvertBack(object value, Type targetType,
object parameter, System.Globalization.CultureInfo culture)
{
throw new NotSupportedException();
}
}

Now, the last and only thing left to do is to declare
DivideDoubleByTwoConverter in your accessible resources so that you
can use it in your XAML file as a StaticResource. I personnally
declare those converters in the Window's or Page's resources, as I
tend to reuse them quite a lot:

<... xmlns:local="clr-namespace:MyNameSpace.MyAssembly" ...>

<Window.Resources>
<localivideDoubleByTwoConverter
x:Key="DivideDoubleByTwoConverter"/>
</Window.Resources>

It's quite complicated, and I hope the WPF team will add a possible
value for CenterX and CenterY (or maybe just Center as a Point?) so
that ScaleTransforms and RotateTransforms can be automatically
centered in the control!
Luc

On Jul 25, 9:37 pm, "Terraslate"
<terraslate.terrasl...@hotmail.hotmail.com.com> wrote:
> is this even possible? from what i have read about dynamic resources they
> seem just what i need - if i understand it properly.
>
> finding an example of who used one to achieve anything like this is however
> a nightmare. my preumption is that i could refer to a property on an object
> i defined in xaml - so i want the scametransform centerx to be the width of
> the button / 2 and the centery to be the height of the button /2.
>
> i have no idea how to acheive this. anyone know how or have i completly
> missed the mark with what DynamicResources are?
>
> cheers

thanks very much - sorry for the delay in responding

i haven't tried it yet - but it looks good. since then i have read an
excellent book by chris sells on wpf - now it all makes sense. like you - i
hope they sort out the centrex, centreY issue as its a pretty common
scenario to want those things smack bang in the centre of the control.


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