bug(linux): ldml keyboard desynchronizes and can crash when bksp is used in non-compliant app with decomposed cluster on Wayland

[mcdurdin]

The test keyboard bksp_ldml can be used to test this with a non-compliant app such as Chrome, in Wayland.

• bksp_ldml.zip

Type the sequence abc     d/, then press Bksp.

First: note that both the d and the combining acute are deleted with a single keystroke, which is unexpected - only the combining acute should have been deleted.

After this, backspace to remove the entire text, and retype a few times. Eventually, the backspace will 'stick' and the app or OS may even crash.

This emerged from testing in #15488.

Example run, Ubuntu 24.04, Wayland, Chrome, with #15488 code

bksp-non-compliant-stuck.mp4

[ermshiperete]

@mcdurdin Do you also get the stuck Enter key with non-compliant apps?

[mcdurdin]

@mcdurdin Do you also get the stuck Enter key with non-compliant apps?

Yes, just tested this scenario with Chrome on Wayland and do get the stuck Enter key. (I don't think we have an open issue for this yet?)