What I have are several very simple maps that are used to show ACS scripted cutscenes - and that's all they are used for. The maps themselves are just a small square room with a player start in it. The walls, floors and ceilings are totally black textures. The lines and sectors are hidden via the appropriated editing flags. The sector is set to silent. The HUD and status bar are hidden when entering the maps. In addition, the player is frozen and also given a "fake weapon" that makes no noise, uses no ammo, can't be changed away from, doesn't have any tags and uses the TNT1A0 sprite.
In other words, I've been pretty thorough and there is nothing to be seen in the level at all.
Then, using ACS, I put various graphics up on screen, play sounds, put up text, whatever. Typical cutscene stuff.
The graphics that I put on screen are placed with HUD_Messages, and they draw over the top of everything, including the automap. I have made them wider than my monitor, and I have tried making some of them very wide.
The problem is, monitors just seem to keep getting wider (e.g. 3840x1080). If the map is being looked at with the normal play window, this isn't a problem. Due to all the precautions I have taken, the area either side of the picture is black. However, if someone with an ultra-wide monitor presses the tab key during one of these cutscenes, the automap will show at the edges. This means that the blue textured background (in my case) automap background can be seen, as can any bits of information that the player might have active such as kill, secret, item counts, level time etc. It just spoils the whole thing.
So, is there anything I can do to block/hide/deactivate/override the automap on such maps so that it just looks black? I can't keep making wider and wider and wider graphics. There's already more black bordering on some of them than there is image! I mean, even if there was some way to get the screen resolution and then tile black images across the extra space or something it would be better than making wider images all the time - and be future proof!
This is just a quick example. It's not ideal, and far from the widest I've tried, but it shows the problem (graphics reduced in size for sanity).
How it's meant to look on a monitor wider than the picture (i.e. how it appears in the game window):

This is what happens if the player presses tab.
