I'm talking about desktop streaming here. Lets say you select a desktop area of 200*800 pixels. It will get shrunk (or stretched) to fit the current output size and get horribly distorted. It can be fixed manually by editing the values in the "Position" tab to add some blank space, in this case on left and right, to get the correct proportions (like manycam does it). But it takes time to calculate how much needs to be substracted and to change the values by hand.
So my idea is to make a checkbox called "Keep Aspect Ratio" and have those values changed automatically. I tried to implement it myself and got it partially working but I got a bit lost in your code and my settings kept being reverted every time I selected the "Position" tab.