Why is my RenderTransform only occuring once?

Question

I have a rectangle and on my MouseMove event I want to transform the rectangle whenever the rectangle's width has changed.

I have code sorta like this:

private Rectangle _rectangle;

public override void OnApplyTemplate()
{
    base.OnApplyTemplate();

    _rectangle = GetTemplatedChild("PART_RangeRectangle") as Rectangle;
    if(_rectangle != null)
    {
        _rectangle.MouseMove += new MouseEventHandler(_rectangle_MouseMove);
    }
}

private void _rectangle_MouseMove(object sender, MouseEventArgs e)
{
    if(e.LeftButton == MouseButtonState.Pressed && _rectangle != null)
    { 
        _rectangle.Width += 50;
        _rectangle.RenderTransform = new TranslateTransform(-10, 0);
    }
}

My Xaml looks sorta like this:

<Grid>
    <Canvas>
        <Rectangle Name="PART_RangeRectangle" StrokeThickness="5"
            RenderTransformOrigin="0.5, 0.5" />
    <Canvas>
</Grid>

When I first trigger the MouseMove event the translation occurs as expected. But this only occurs once. I am getting into that block of code and the width of the rectangle is updating fine, but I've yet to figure out why the transform is not updating.

for giggles I did try replacing a RenderTransform with a LayoutTransform but nothing happened. — Ashley Grenon, Feb 08 '12 at 20:30
here is a Link that may help you look at this and see if it sheds some light.. http://wpftutorial.net/Behaviors.html — MethodMan, Feb 08 '12 at 20:48
I'm creating a custom control and in the template for the control I have this rectangle. I use GetTemplatedChild("PART_RangeRectangle") to gain access to it from code. That's what _rectangle is. I'll update the code to show my OnApplyTemplate method. — Ashley Grenon, Feb 08 '12 at 20:49

kitti · Accepted Answer · 2012-02-08T21:06:11.573

2

You're replacing the old transform with an identical transform. You need to modify the existing transform and use += like you do with Width.

Example:

if (_rectangle.RenderTransform is TranslateTransform)
{
    (_rectangle.RenderTransform as TranslateTransform).X -= 10;
}
else _rectangle.RenderTransform = new TranslateTransform(-10, 0);

edited Feb 08 '12 at 21:06

answered Feb 08 '12 at 20:56

kitti

14,663
31
49

can you provide an example of that? – Ashley Grenon Feb 08 '12 at 21:02
Ahhhhh...I see. Doh! I'm so used to dealing with transforms in xaml @_@ I made this more difficult that it had to be. I knew it was something simple! Thanks! – Ashley Grenon Feb 08 '12 at 21:08

score 1 · Answer 2 · answered Feb 08 '12 at 20:56

1

You're not changing your transform. Assigning a RenderTransform does not move the rectangle, it sets an offset. You're not changing that offset after your first assignment.

answered Feb 08 '12 at 20:56

500 - Internal Server Error

28,327
8
59
66

Why is my RenderTransform only occuring once?

2 Answers2