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bug#38049: C mode fontification broken with reposition-window
From: |
Alan Mackenzie |
Subject: |
bug#38049: C mode fontification broken with reposition-window |
Date: |
Sat, 9 Nov 2019 14:45:17 +0000 |
User-agent: |
Mutt/1.10.1 (2018-07-13) |
Hello, Juri.
On Tue, Nov 05, 2019 at 21:07:37 +0000, Alan Mackenzie wrote:
> On Sun, Nov 03, 2019 at 22:28:05 +0200, Juri Linkov wrote:
> > Version: 27.0.50
> > This is a reproducible test case:
> > 0. emacs -Q
> > 1. C-x C-f emacs/lib-src/emacsclient.c
> > 2. M-: (progn (search-forward "create-frame" nil t) (reposition-window))
> > Then half screen displays unfontified lines.
> > Fontification doesn't fail in other modes, only in C mode.
> > This has something to do with interaction between c-font-lock
> > and buffer navigation in reposition-window.
> Indeed it does.
> Briefly,
> (i) reposition-window narrows to (2758 3940) in
> repos-count-screen-lines.
> (ii) This latter function uses vertical-motion to count the lines.
> (iii) vertical-motion triggers jit-lock fontification.
> (iv) This calls (eventually) c-font-lock-fontify-region.
> (v) c-font-lock-fontify-region attempts to examine buffer text before
> the start of the jit-lock chunk to find syntactic context.
> (vi) This is outside the visible region, so Emacs raises an exception.
> (vii) The exception is caught and discarded by an unwind-protect in
> c-font-lock-fontify-region.
> (viii) The jit-lock chunk remains unfontified.
[ .... ]
I have fixed this bug by widening around c-font-lock-fontify-region. I
am closing the bug with this post.
--
Alan Mackenzie (Nuremberg, Germany).