I think the the problem mentioned above is more general than described -- it's not just switching keyboard layouts while SDL is running, but that the x part of ctrl+x is only available via scancode or key symbol which don't go through translation for the current OS keyboard layout.

As an example, an emacs-like editor on simulated hardware. I'm using a DVORAK mapping in Ubuntu.
Type some text:

1. physical keys k
2. physical keys j
3. physical keys d
4. I see the characters t h e (via text input)

Using the alt key as a modifier

1. Press physical key alt and hold
2. Press the physical key n
3. Grab the printable part of the chord from text input, n mapped to b
4. Read the modifier to determine the alt is depressed
5. I can figure out that the command alt+b was intended! (hack, but it works)

However: using the ctlr key as a modifier

1. press physical key ctrl and hold
2. press the physical key n
3. No text input event generated, so I have to use key up and key down events and grab the sym/scancode, which isn't mapped.
4. I still know ctrl is the modifier, but I have no way to know that the user is using the DVORAK keyboard and n is mapped to b

This is related to issue: #3586, which is closed. But I think it wasn't realized how problematic this is for certain applications.

Also, maybe I'm missing something? or there's a work-around! In any case thanks for all the great work!