Bug#1100487: w3m: bad display with image and U+2060 WORD JOINER

[Vincent Lefevre]

Package: w3m
Version: 0.5.3+git20230121-2.1
Severity: normal

There is a display issue when one has an image (valid or not) and
text with the U+2060 WORD JOINER character.

I've attached a testcase, which contains something like:

<p>Text.</p>
[...]
<p>Text.</p>
<p><img src="data:image/png;base64," alt=""/></p>
<p>foo&#x2060;bar abcdef.</p>

Search for "ab", then move the cursor to the right up to the end.
One successively gets:

foo⁠bar aacdef.
foo⁠bar aabdef.
foo⁠bar aabcef.
foo⁠bar aabcdf.
foo⁠bar aabcde.
foo⁠bar aabcdef
foo⁠bar aabcdef.

Alternatively, put the cursor at the end ([End] key), then at the
beginning of the "foo⁠bar abcdef." line, then move the cursor to
the right: same display issue starting with "bar".

It is important that the test part is not displayed on the first page,
hence the sequence of paragraphs. Note that this issue disappears if
either the image or the U+2060 WORD JOINER character is removed.

I first noticed this issue on

  https://bugzilla.mozilla.org/show_bug.cgi?id=1876874

when I was searching for "C\+\+" (specifically "of C\+\+").

-- System Information:
Debian Release: trixie/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'stable-updates'), (500, 
'stable-security'), (500, 'stable-debug'), (500, 'proposed-updates-debug'), 
(500, 'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 6.11.10-amd64 (SMP w/12 CPU threads; PREEMPT)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, 
TAINT_UNSIGNED_MODULE
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages w3m depends on:
ii  libc6       2.41-4
ii  libgc1      1:8.2.8-1
ii  libgpm2     1.20.7-11+b2
ii  libssl3t64  3.4.1-1
ii  libtinfo6   6.5+20250216-2
ii  zlib1g      1:1.3.dfsg+really1.3.1-1+b1

Versions of packages w3m recommends:
ii  ca-certificates  20241223

Versions of packages w3m suggests:
pn  brotli          <none>
ii  bzip2           1.0.8-6
pn  cmigemo         <none>
pn  compface        <none>
ii  curl            8.12.1-3
ii  dict            1.13.1+dfsg-1
ii  dict-wn         1:3.0-39
ii  dictd           1.13.1+dfsg-1
pn  libsixel-bin    <none>
hi  mailcap         3.70+nmu1
ii  man-db          2.13.0-1
ii  media-types     13.0.0
ii  sensible-utils  0.0.24
ii  w3m-el          1.4.632+0.20210201.2305.54c3ccd-3
ii  w3m-img         0.5.3+git20230121-2.1
ii  wget            1.25.0-2
ii  xdg-utils       1.2.1-2
pn  xsel            <none>

-- no debconf information

-- 
Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / Pascaline project (LIP, ENS-Lyon)

Title: Test with image and U+2060 WORD JOINER for w3m

With w3m:

1. Search for ab (type /ab below this text).
2. Then move the cursor to the right with the right arrow.

Text.

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foo⁠bar abcdef.