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Levels of font lock – Dired, Dired+ and Diredful
From: |
Yuri Khan |
Subject: |
Levels of font lock – Dired, Dired+ and Diredful |
Date: |
Mon, 22 May 2017 16:48:52 +0700 |
Hello list,
I just spent an hour investigating an interaction of multiple packages
tinkering with font lock. I’m pretty sure I ought to file a bug report
but not so sure against what.
There is a concept of levels of font lock. A major mode sets up three
lists of keywords in a buffer-local ‘font-lock-defaults’ variable.
Then, depending on the user’s ‘font-lock-maximum-decoration’, more or
fewer keywords get applied.
The base Dired mode defines only one level:
(setq-local font-lock-defaults
'(dired-font-lock-keywords t nil nil beginning-of-line))
Dired+ by Drew Adams, in its dired-mode-hook handler, replaces that
with a three-element list with two different sets of keywords:
(set (make-local-variable 'font-lock-defaults)
;; Two levels. Use 3-element list, since it is
standard to have one more
;; than the number of levels. This is necessary for
it to work with
;; `font(-lock)-menus.el'.
'((dired-font-lock-keywords
dired-font-lock-keywords
diredp-font-lock-keywords-1)
t nil nil beginning-of-line))
Diredful by Thamer Mahmoud keeps a list of rules for highlighting
files by extension, file name regexp, or full Dired line regexp, and
provides a convenient UI for editing these rules. Behind the scene, it
adds keywords to ‘dired-font-lock-keywords’:
(add-to-list 'dired-font-lock-keywords
(list regexp face-list))
Now the problem is when I use both of these together. I play on the
Insane level (font-lock-maximum-decoration set to t). It appears that
I “only” get the last level of font lock —
‘diredp-font-lock-keywords-1’ from Dired+. I do not get the additions
by Diredful.
I can work around the issue by changing Diredful to add to both lists
(dired-font-lock-keywords and diredp-font-lock-keywords-1). But this
feels wrong; Diredful should not have to know about Dired+.
On the other hand, I can work around the issue by changing Dired+ so
that instead of ‘diredp-font-lock-keywords-1’ it uses a new variable
which is set in the same dired-mode-hook handler to the result of
(append dired-font-lock-keywords diredp-font-lock-keywords-1). This
feels cleaner but now it’s highly probable that some of Dired+’s
keywords duplicate and/or override those of base Dired.
What do you think?
- Levels of font lock – Dired, Dired+ and Diredful,
Yuri Khan <=