WPF client to screen point transformation

问题

I'm looking for a way to transofrm given points that are relative to a Visual to Points on the screen. I found this solution:

http://social.msdn.microsoft.com/Forums/vstudio/en-US/b327c0bc-d27e-44fe-b833-c7db3400d632/how-to-get-control-location-in-screen-coordinate-system

I can't understand the different beween the pointRoot and the pointClient as they seem to be equal all the time:

// [...]
// Translate the point from the visual to the root.
GeneralTransform transformToRoot = relativeTo.TransformToAncestor(root);
Point pointRoot = transformToRoot.Transform(point);

// Transform the point from the root to client coordinates.
Matrix m = Matrix.Identity;
Transform transform = VisualTreeHelper.GetTransform(root);
if (transform != null)
    m = Matrix.Multiply(m, transform.Value);

Vector offset = VisualTreeHelper.GetOffset(root);
m.Translate(offset.X, offset.Y);
Point pointClient = m.Transform(pointRoot);
// [...]

(for the full code click on the link)

It seems that the VisualTreeHelper.GetOffset(root) tries to get the transform of the window...

回答1:

Assuming that your Visual comes from a Button control... are you looking for something like this?:

Point locationFromWindow = button1.TranslatePoint(new Point(0, 0), this);

Point locationFromScreen = button1.PointToScreen(locationFromWindow);

Note: these are both methods of the Visual class, so you can also call them from your Visual directly.

来源：https://stackoverflow.com/questions/18103540/wpf-client-to-screen-point-transformation