I have:
(setq mode-line-end-spaces "string")
That displays string in the mode-line.
How can I get string in red there?
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2 Answers
You need to create a string with the appropriate face. You do that by attaching a face text property to the string, giving it value of some face (predefined or defined for the specific purpose - you can look at all the predefined faces with M-x list-faces-display and pick one from there, or you can define your own face).
E.g. here's a snippet to use a predefined face:
(setq s (copy-sequence "sring"))
(put-text-property 0 6 'face 'custom-invalid s)
(setq mode-line-end-spaces s)
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1I understand. To generalize your answer, I'll try to write a function that, given a string, returns a propertized string.– GabrieleCommented Jul 23, 2020 at 14:02
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You should not try to modify a constant string:
(setq s (copy-sequence "string")).– user19761Commented Jul 25, 2020 at 11:43 -
OK - edited. Here are some links to provide some context: When to use quote for lists? Modifying quoted lists in Elisp and Which Lisp objects are byte-compiled? plus a similar complaint by @Fólkvangr on an answer of mine that I have not fixed.– NickDCommented Jul 27, 2020 at 19:03
@NickD provided a good answer: use a face.
OP's comment to Nick's answer says that he'll try to write a function that, given a string, returns a propertized string. Such functions already exist: propertize does that, and so does add-face-text-property.
For example:
(setq ss (propertize "abcde" 'face '(:foreground "red")))
or
(setq ss "abcde")
(add-face-text-property 0 (length ss) '(:foreground "red") nil ss)
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You should not try to modify a literal string:
(setq ss (copy-sequence "abcde")).– user19761Commented Jul 25, 2020 at 11:42 -
@Fólkvangr: Depends on what behavior you want. Do you want to modify a copy of the original string or the original string? The example of using a literal string here is also for brevity - who knows where the actual original string comes from? But if the intention is to modify the original string, then you don't want to use
copy-sequence.– DrewCommented Jul 25, 2020 at 16:15 -
@Drew:
copy-sequenceallows to create a mutable string (c.f. Elisp manual version 27, section 2.9 Mutability). In your sample code,add-face-text-propertymodifies a literal string.– user19761Commented Jul 25, 2020 at 17:19 -
@Fólkvangr: Yes, I know. And? If you can modify something then it's mutable. But all of this is extraneous. If you prefer, read "Suppose that the value of
ssis a string", instead of thesetq. The point of the answer is that you can useadd-face-text-propertyto add color to a string.– DrewCommented Jul 25, 2020 at 18:15