I have a raspberry pi zero and I'm running Jessie lite (very similar to ubuntu distros). I'm using my pi to run a MagicMirror. Everything runs correctly but X windows does not take up the whole screen. The command line view does take up the whole screen, however. My framebuffer is set to 1280x1024 which I think is the correct resolution for my monitor, but when running my kiosk (kweb) browser in X windows (or anything else started with xinit) I only use up about 2/3 of the screen for both height and width. I'm using matchbox as my window manager. Does anyone know what would be causing this and how I can get my application to use the whole screen?
Common LCD monitors these days are larger then 1280x1024. Look at your monitor's documentation and don't guess what the size is. The command line view is text mode and the monitor is probably already programmed to take a standard 80x25 character size and fit the screen with it.