layout: allow stretching the layout by a small amount

Due to the way the panel size is calculated, there might be a small empty space on the sides or top of the layout. This can be an issue, especially when this empty space is located on the sides, as touch events in this area are not taken into account.

By allowing a small difference in horizontal and vertical scaling, we can ensure the panel occupies the whole display width in cases where this would be problematic.

Quick fix for #334 (closed) meant for being applied on top of !543 (merged)