Question

I have three canvases I’m using in a card game app I’m building. One is the main canvas that has the other two as child canvases (one static and one that will rotate):

In this sample app, I want to move the RotatingEl to the position on the StaticEl:

When i click the Move button, it works as expected:

Now, I want to Rotate the RotatingCanvas and still have the RotatingEl move to the StaticEl location AND adjust rotation to still match the StaticEl’s angle:

When I try it, it moves to the wrong location:

Here is my code on the Move Button Click:

GeneralTransform generalTransformStaticEl = StaticEl.TransformToVisual(MainCanvas);
        Point pointstatic = generalTransformStaticEl.Transform(new Point()); 
        GeneralTransform generalTransformRotEl = RotatingEl.TransformToVisual(MainCanvas);
        Point pointrot = generalTransformRotEl.Transform(new Point());

        double distancecalcX = pointstatic.X - pointrot.X;
        double distancecalcY = pointstatic.Y - pointrot.Y;

        DoubleAnimation ELMoveY = new DoubleAnimation();

        ELMoveY.From = Canvas.GetTop(RotatingEl);
        ELMoveY.To = Canvas.GetTop(RotatingEl)+(distancecalcY);
        ELMoveY.Duration = new Duration(TimeSpan.FromSeconds(1.0));

        DoubleAnimation ELMoveX = new DoubleAnimation();

        ELMoveX.From = Canvas.GetLeft(RotatingEl);
        ELMoveX.To = Canvas.GetLeft(RotatingEl)+(distancecalcX);
        ELMoveX.Duration = new Duration(TimeSpan.FromSeconds(1.0));

        RotatingEl.BeginAnimation(Canvas.LeftProperty, ELMoveX);
        RotatingEl.BeginAnimation(Canvas.TopProperty, ELMoveY);

How can I adjusted the “To” of the animations to still move the Rotated canvas’s RotatingEl to the static StaticEl’s position AND adjust the rotation of the RotatingEl to match the StaticEl’s orientation?

Answer 1

I found my own solution. In case anyone may be interested, here is the updated code:

double foundangle = 0;
        //verify an actual transform group is there before getting rotate angle
        if (RotatingCanvas.RenderTransform.Value.ToString() != "Identity")
        {
            RotateTransform rt = (RotatingCanvas.RenderTransform as TransformGroup).Children[2] as RotateTransform;
            foundangle = rt.Angle;
        }
        RotateTransform rottrans = new RotateTransform(foundangle*-1);
        RotatingEl.RenderTransform = rottrans;
        GeneralTransform generalTransformStaticEl = StaticEl.TransformToVisual(RotatingCanvas);
        Point pointstatic = generalTransformStaticEl.Transform(new Point());

        DoubleAnimation ELMoveY = new DoubleAnimation();

        ELMoveY.From = Canvas.GetTop(RotatingEl);
        ELMoveY.To = pointstatic.Y;
        ELMoveY.Duration = new Duration(TimeSpan.FromSeconds(1.0));

        DoubleAnimation ELMoveX = new DoubleAnimation();

        ELMoveX.From = Canvas.GetLeft(RotatingEl);
        ELMoveX.To = pointstatic.X;
        ELMoveX.Duration = new Duration(TimeSpan.FromSeconds(1.0));

        RotatingEl.BeginAnimation(Canvas.LeftProperty, ELMoveX);
        RotatingEl.BeginAnimation(Canvas.TopProperty, ELMoveY);

The generalTransformStaticEl required co-ordinates from the rotated canvas instead of the non-rotated MainCanvas. The adjustment to rotation was simply a matter of getting the Rotated canvas’s current rotation angle and multiplying by -1 to align with static rectangle