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I have a package which checks the face of a character before operating on it.

A problem with this is, the face might not yet have been calculated because of:
jit-lock-context-time, which delays contextual fontification.


How can I ensure a region of text has all it's font-faces calculated, including contextual fonts?

  • Why do you check the face of characters the buffer? Historically, I've done it as well, but got bitten so many times that I now avoid it at all costs. In most cases, you can use syntax-ppss instead. – Lindydancer Apr 17 at 9:43
  • I'd like to run a spell checker over comments, ignoring code or other symbols in the comments. – ideasman42 Apr 17 at 10:19
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    syntax-ppss returns a list that describes the context. Element 4 in this is non-nil when in a comment. This is a much more robust way than to check font-lock faces. (However, this does not solve the problem of ignoring other things within comments, like code.) – Lindydancer Apr 17 at 14:20
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font-lock-ensure does exactly that. There's also font-lock-fontify-buffer for interactive use and older Emacsen that do not have font-lock-ensure yet, hence you'll often see the following construction:

(if (fboundp 'font-lock-ensure)
    (font-lock-ensure)
  (with-no-warnings
    (font-lock-fontify-buffer)))

Note that it may be necessary to call font-lock-flush before font-lock-ensure to tell font-lock that a certain font-lock region is outdated.

| improve this answer | |
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    Maybe, it is worth noting that if one switches on some minor mode that adds/changes/removes some font-lock keywords one should run font-lock-flush before font-lock-ensure. – Tobias Apr 17 at 8:18
  • @Tobias this should be made part of the answer - since font-lock-ensure on it's own wasn't working. The issue with flushing is it causes re-fontification, I'd like just to do remaining fontification, instead of adding extra work. – ideasman42 Apr 17 at 8:21
  • font-lock-ensure does the remaining fontification and font-lock-flush is the big hammer when that doesn't work. I've edited the answer appropriately. – wasamasa Apr 17 at 9:28

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