What is the best way to show a WPF window at the mouse location (to the top left of the mouse)?

In the end, this did the trick:

        protected override void OnContentRendered(EventArgs e)        {            base.OnContentRendered(e);            MoveBottomRightEdgeOfWindowToMousePosition();        }        private void MoveBottomRightEdgeOfWindowToMousePosition()        {            var transform = PresentationSource.FromVisual(this).CompositionTarget.TransformFromDevice;            var mouse = transform.Transform(GetMousePosition());            Left = mouse.X - ActualWidth;            Top = mouse.Y - ActualHeight;        }        public System.Windows.Point GetMousePosition()        {            System.Drawing.Point point = System.Windows.Forms.Control.MousePosition;            return new System.Windows.Point(point.X, point.Y);        }

Can you not use something like this?:

Point mousePositionInApp = Mouse.GetPosition(Application.Current.MainWindow);Point mousePositionInScreenCoordinates =     Application.Current.MainWindow.PointToScreen(mousePositionInApp);

I haven't been able to test it, but I think it should work.

UPDATE >>>

You don't have to use the Application.Current.MainWindow as the parameter in these methods... it should still work if you have access to a Button or another UIElement in a handler:

Point mousePositionInApp = Mouse.GetPosition(openButton);Point mousePositionInScreenCoordinates = openButton.PointToScreen(mousePositionInApp);

Again, I haven't been able to test this, but if that fails as well, then you can find one more method in the How do I get the current mouse screen coordinates in WPF? post.

You can also do this by slightly modifying your initial example and positioning the window before showing it.

MyWindowObjectThatInheritsWindow window = new MyWindowObjectThatInheritsWindow();var helper = new WindowInteropHelper(window);var hwndSource = HwndSource.FromHwnd(helper.EnsureHandle());var transformFromDevice = hwndSource.CompositionTarget.TransformFromDevice;System.Windows.Point wpfMouseLocation = transformFromDevice.Transform(GetMousePositionWindowsForms());window.Left = wpfMouseLocation.X - 300;window.Top = wpfMouseLocation.Y - 240;window.Show();