Oh, my goodness! This is actually working! Thank you so much, you saved my hide. I can’t tell you how long I spent trying to fix this myself.
It’s still slightly off, there’s a growing gap between the real cursor and in-game cursor, which is the size of the boarders filling the space in the window that the RenderTarget doesn’t cover. That’s what “R” is, it’s the RenderTarget size and the size of the boarder (X and Y are the boarder size, one is always 0 because the boarders are either up/down or left/right. It’s a Rectangle returned from the CalculateRenderTargetPosition() method). I’m not too concerned about it, I can fiddle with it some more later, try and find a place where to put the R values. I just wanted to thank you.