Been thinking about how to change the screen ratio in emulation without distorting the pixel shapes. There is a mod for Super Mario World doing this:
https://github.com/VitorVilela7/wide-snesThe mod works because the unmodified game already simulates a wider playfield than the screen and the player can move the view left or right with the shoulder buttons, but making the mod still required a ton of tweaks. There is no general method of simply expanding the view port of old games since they usually don't simulate a bigger area than what the player sees in the moment.
It occurred to me that it is not necessary to reverse-engineer game code to rearrange where the HUD appears. In principle an emulator can just modify the screen output based on registering certain pixel patterns. This can also be used to change illustrations on the frame around the playfield based on the level the player is in.
It's also possible to implement achievements with that as long as the game has unambiguous pixel patterns for that, think the score in the HUD reaching X digits or a cutscene playing. There are already achievements modded into old games, see:
https://retroachievements.org/ …but these seem to be hard to program. What I'm thinking about could be "programmed" by playing and marking a section of the screen when a particular event is triggered that makes that screen section look like that.
Now this seems like an obvious idea. Does it already exist?