ScaleTransform transforms non-linearly

Posted by Chris on Stack Overflow See other posts from Stack Overflow or by Chris
Published on 2010-06-08T11:19:50Z Indexed on 2010/06/08 11:22 UTC
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I am using scale transform to allow a user to resize a control. What happens though is that when you start to move the mouse the control jumps to a new size, and then scales oddly. The further you move your mouse from the starting location the larger the increase in size becomes.

I expect its the way I calculate the scale to be applied. Here is the code:

private void ResizeGrip_MouseDown(object sender, MouseButtonEventArgs e)
{
    ResizeHandle.CaptureMouse();

    //Get the initial coordinate cursor location on the window
    initBtmX = e.GetPosition(this).X;

    bottomResize = true;
}

private void ResizeGrip_MouseUp(object sender, MouseButtonEventArgs e)
{
    bottomResize = false;
    ResizeHandle.ReleaseMouseCapture();
}

private void ResizeGrip_MouseMove(object sender, MouseEventArgs e)
{
    if( bottomResize == true)
    {
        //Get the new Y coordinate cursor location
        double newBtmX = e.GetPosition(this).X;


        //Get the smallest change between the initial and new cursor location
        double diffX = initBtmX - newBtmX;

        // Let our rectangle capture the mouse
        ResizeHandle.CaptureMouse();

        double newWidth = e.GetPosition(this).X - diffX;

        double scaler = newWidth / ResizeContainer.ActualWidth;

        Console.WriteLine("newWidth: {0}, scalar: {1}", newWidth, scaler);


        if (scaler < 0.75 || scaler > 3)
            return;

        ScaleTransform scale = new ScaleTransform(scaler, scaler);

        ResizeContainer.LayoutTransform = scale;
    }
}

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