I often like to play older games (with Cedega or Wine) on my laptop, but those games often don't have widescreen (16:9 or 16:10) support. As a result, those games would normally be stretched out on a widescreen monitor. To circumvent this, I usually connect my external monitor, but when I'm not at home, this is not really an option. There is an option however which disables monitor stretching, and allows me to play the game in a more normal resolution:
Option "Centermode" "on"
This disables display stretching. Note that for this to work as I intended it, you need to match the vertical resolution of the game as close to the maximum of your native vertical resolution as possible. This will result in having black borders left and right of the display, but at least, the aspect ratio will be correct.
