ActionScript 2.0

 
// functions to enter and leave full screen mode
function goFullScreen() {
	Stage["displayState"] = "fullScreen";
}
function exitFullScreen() {
	Stage["displayState"] = "normal";
}
// function to enable, disable context menu items, based on which mode we are in.
function menuHandler(obj, menuObj) {
	if (Stage["displayState"] == "normal") {
		// if we're in normal mode, enable the 'go full screen' item, disable the 'exit' item
		menuObj.customItems[0].enabled = true;
		menuObj.customItems[1].enabled = false;
	} else {
		// if we're in full screen mode, disable the 'go full screen' item, enable the 'exit' item
		menuObj.customItems[0].enabled = false;
		menuObj.customItems[1].enabled = true;
	}
}
// create a new context menu
var fullscreenCM:ContextMenu = new ContextMenu(menuHandler);
// hide the regular built-in items
fullscreenCM.hideBuiltInItems();
// now, add the items to enter and leave full screen mode
var fs:ContextMenuItem = new ContextMenuItem("Go Full Screen", goFullScreen);
fullscreenCM.customItems.push(fs);
var xfs:ContextMenuItem = new ContextMenuItem("Exit Full Screen", exitFullScreen);
fullscreenCM.customItems.push(xfs);
// now, attach the context menu to any movieclip in your movie.
// here we attach it to _root, (even though using _root is generally a bad idea,)
// so it will appear if you right click anywhere on the movie.
_root.menu = fullscreenCM;