how to let a layout cover the whole screen?

I've (hopefully) solved my problem with the following hack:

let ScreenWidth  = g.getWidth();
let ScreenHeight = g.getHeight();

let AppRect = Bangle.appRect;
Bangle.appRect = { x:0,y:0, w:ScreenWidth,h:ScreenHeight, x2:ScreenWidth-1,y2:ScreenHeight-1 };

Before entering a configuration screen, I run the code mentioned above - when leaving it, I simply restore Bangle.appRect from AppRect.

Important note: Bangle.appRect must be set to fullscreen again whenever a new layout shall be calculated/rendered