查找Wpf WindowsFormsHost中托管的Winforms控件的中心

Question

I am in the process of converting a Winforms project to WPF, and in doing so I have hit a very particular issue. Allow me to explain. Within my project I am using OpenTK, which means I need to host the GLControl within a WindowsFormHost. The GLControl makes use of a First Person Camera, and for it to work I need to calculate the exact center of the GLControl, which is where I place the mouse when the user is "looking around". Here is an example of my application in WPF:

The function that I had previously used in WinForms was:

        public static Point FindCenterOfControl(Form parent, Control control)
        {
            Point location = parent.PointToScreen(control.Location);
            return new Point(location.X + control.Width / 2, location.Y + control.Height / 2);
        }

But naturally, this does not work in WPF. I have tried various parameters, but I keep getting null crashes, mainly from my GLControl, which apparently no longer uses the "Location" property when it's hosted within a WPF application. So, quite frankly, I am at a loss of how to accomplish this.

As another note, my code works as long as I guess where the center should be. I can move the camera around and it looks just fine. The issue arises when I resize the window, because then the center is nowhere near where it should be and my first person camera goes ballistic. I need a way to replicate my previous function of calculating the absolute center of a control within my WPF application.

Does anyone have any ideas how I can convert my old function to something that supports hosted controls within a WPF environment?

Answer 1

Nevermind, I found a solution, or at least...a dirty hack perhaps. The trick was to not try and find the center of my GLControl, but find the center of the WindowsFormsHost instead. Here is my code so that it may help someone else in the future.

        public Point FindCenter()
        {
            System.Windows.Point relativePoint = _host.TransformToAncestor(_parent).Transform(new System.Windows.Point(0, 0));
            return new Point((int) (relativePoint.X + _host.ActualWidth / 2), (int) (relativePoint.Y + _host.ActualHeight / 2));
        }

Update:

As it turns out, the above method was actually wrong. It centered my cursor at a predefined location regardless of my window size or position. This location was wrong. I have crafted a new method, however, which gives the desired result.

        public Point FindCenter()
        {
            System.Windows.Point relativePoint = _host.PointToScreen(new System.Windows.Point(0, 0));
            return new Point((int)(relativePoint.X + (this.Width/2)), (int)(relativePoint.Y + (this.Height/2)));
        }

That method DOES center the cursor on the control at the correct location. If you're going to use this within your own application I would suggest trying both to make certain which one suits your needs.