Fullscreen Tools contains a collection of simple tools to force applications into fullscreen mode by different means. Those are right now mostly just hacks and might not work without some customization in the source code. Also no actual resolution switching is provided right now, use xrandr for that.
For compilation type:
mkdir build cd build cmake .. make
Create a window with a simple black background and captures another applications window in it. The parent window can be resized and put into fullscreen mode. Useful in cases where an application requires a resolution or aspect ratio not supported by your monitor or graphics card and you want to fill the surrounding space with a letter box.
Removes window decorations, sets override redirect and moves window to the top/left of the screen. Useful for applications that don't support fullscreen properly in multi monitor configurations.
Displays the hierachy of windows in X11, mainly useful for debugging or getting the window id of subwindows.
sdl-hack is a simple LD_PRLOAD based hack that lets you get between SDL and a game to override specific behaviour. For example if a game requests fullscreen mode and provides no option to switch to window mode, you can force it to be in window mode.