Setting a custom resolution in windowed mode

Is it possible? There's no option for that in the game, the only way I had of setting the game to the resolution I want to is to drag the window around, take a screenshot and check it's properties to know at wich resolution I'm at.

So isn't there a better method than this, like a command line or something? Because there's a -windowed line but nothing to set up a resoution like -width xxxx -height xxxx. Anything really.

just choose a custom resolution and take the screen shot in fullscreen

unfortunately there isn't a way to do this. the best you can do is set your monitor to "no scaling" and then pick a resolution in full screen mode.