set-text-properties and jit-lock-mode

[Alan Schmitt]

Hello,

I'm tracking down a bug in ledger-mode and I'm now at the point where I
think I need some help about some emacs core code.

The problem: if jit-lock-mode it t, then using set-text-properties to
change the face does not work.

To reproduce: start emacs with -Q. In the scratch buffer, type "foo".
Then evaluate:
(set-text-properties 192 195 (list 'face 'italic))

Nothing changes, and when I do a `describe-char' on one letter of "foo"
I don't see the face.

If I then evaluate
(setq jit-lock-mode nil)
(set-text-properties 192 195 (list 'face 'italic))

then I see the face change to italic, confirmed by `describe-char'.

As `set-text-properties' is a function in C, I don't know how to look at
its source (any pointers on how to do this would be great). Is it
supposed not to work for faces when jit-lock is on?

Thanks,

Alan

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