401045 - a character shows up for a zero-width joiner (U+200D)

Status: RESOLVED WORKSFORME

(Core :: Graphics, defect)

Description

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

The reftest for bug 391045 fails for me on Linux because I see a character for the zero-width joiner in the reference rendering at
http://mxr.mozilla.org/seamonkey/source/layout/reftests/bugs/391045-ref.html .

I think we have a list of characters somewhere in the code (I forget if it's in gfx or layout, but I suspect gfx) for characters that we never display, even if a font claims to have a glyph for them.  Should this be added to that list?  Or was that list my imagination?

Steps to reproduce: load  http://mxr.mozilla.org/seamonkey/source/layout/reftests/bugs/391045-ref.html

Expected results: nothing between the "ര" and the "."

Actual results: A vertical line with a horizontal line at the top (extending a little to the right) between those two characters.

Comment 1

[Robert O'Callahan (:roc) (email my personal email if necessary)]

We can't just strip out ZWJs, because they may affect shaping if I understand correctly. We'd have to post-process the textrun and remove any glyphs generated for ZWJs.

I think we should fix this in gfxPangoFonts somehow.

Comment 2

[Stuart Parmenter]

behdad -- any idea what pango is doing here?

Comment 3

[Behdad Esfahbod]

Are you by any chance compiling against one pango version and running against another?

Comment 4

[Robert O'Callahan (:roc) (email my personal email if necessary)]

David probably isn't, but we often do, of course.

Comment 5

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

No, I'm not.

We could just consider this a bug in the font.  I probably ought to try to figure out which font it is at some point, though.

I filed this partly because I thought we already had a list of characters where we did this so it would be easy.  But maybe it's worth doing anyway.

Comment 6

[Simon Montagu :smontagu]

I think you're thinking of http://mxr.mozilla.org/seamonkey/source/gfx/src/shared/ignorable.x-ccmap, but that deliberately doesn't include ZWJ and ZWNJ.

FWIW I used to have similar issues until I removed the fonts in http://packages.debian.org/etch/ttf-freefont/all/filelist

Comment 7

[Karl Tomlinson (:karlt)]

KhmerOSSys.ttf provides a line with a small x at the top for ZWJ
and a line for ZWNJ.

Comment 8

[Benoit Jacob [:bjacob] (mostly away)]

Does this bug still exist? It doesn't have a testcase I can use right away, and hasn't received attention in 4 years. In the context of a bugkill session that means INCOMPLETE; reopen if necessary.

Comment 9

[Benoit Jacob [:bjacob] (mostly away)]

Oh. Comment 0 does have steps-to-reproduce. The problem can't be reproduced here on linux x86-64 Firefox 11.