Bug 119940 - Bolding a Hebrew word in a sentence with some embedded Hebrew fonts changes the intra-word spacing of surrounding words
Summary: Bolding a Hebrew word in a sentence with some embedded Hebrew fonts changes t...
Status: NEW
Alias: None
Product: LibreOffice
Classification: Unclassified
Component: Writer (show other bugs)
(earliest affected)
Hardware: All All
: medium normal
Assignee: Not Assigned
Keywords: bibisected, bisected
Depends on:
Blocks: Font-Rendering Special-Character RTL-Hebrew
  Show dependency treegraph
Reported: 2018-09-17 20:17 UTC by Idan Miara
Modified: 2019-09-20 03:05 UTC (History)
7 users (show)

See Also:
Crash report or crash signature:

test odt (10.30 KB, application/vnd.oasis.opendocument.text)
2018-09-17 20:18 UTC, Idan Miara
before bolding (72.53 KB, image/png)
2018-09-17 20:18 UTC, Idan Miara
after bolding (72.77 KB, image/png)
2018-09-17 20:18 UTC, Idan Miara

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Description Idan Miara 2018-09-17 20:17:29 UTC
The following bug is related to Hebrew text on LibreOffice it was reproduced on Windows and Linux.
I could not reproduce the problem on MS-Office or with LO-Impress with the same font.
The text is not justified.

Steps to Reproduce:
1. start new document
2. write some Hebrew sentence using the David CLM font (which is the default font on Windows)
3. bold some random word
4. notice that some intra-word spacing on some surrounding words have changed
5. try to bold some other word, other spaces would change...
David CLM font. It can’t be reproduced with English font or with MS-Office with the same font.

Actual Results:
some intra-word spacing on some surrounding words have changed

Expected Results:
no change of intra-word spacing of any other words

Reproducible: Always

User Profile Reset: No

Additional Info:
I'm attaching to pictures, before with a random word bold/not bold
Comment 1 Idan Miara 2018-09-17 20:18:06 UTC
Created attachment 144962 [details]
test odt
Comment 2 Idan Miara 2018-09-17 20:18:24 UTC
Created attachment 144963 [details]
before bolding
Comment 3 Idan Miara 2018-09-17 20:18:42 UTC
Created attachment 144964 [details]
after bolding
Comment 4 Eyal Rozenberg 2018-09-17 20:23:56 UTC
What happens with other Culmus fonts? Other non-Culmus fonts? At different zoom levels?
Comment 5 Idan Miara 2018-09-17 20:37:19 UTC
Different zoom levels - on some zoom levels the bug persists, on others the bold word expands and all the following words move, which I guess is acceptable.
Other fonts: Checking on Windows: I didn't install any specific fonts, just the ones that come with the default installation.
I'm not sure how can I tell which font is from Culmus as I can't find most of them (http://culmus.sourceforge.net/culmus.pdf) I can't find.
For instance, There is a font named Miriam, which doesn't reproduce the problem, and a font named מרים (Hebrew for Miriam) which does reproduce.
Comment 6 Maxim Iorsh 2018-09-17 21:45:06 UTC
The bold word במסמך is 3% narrower than the regular one. It looks like the change in width due to emboldening moves the successive glyphs by a fraction of a pixel, thus making some glyphs move a pixel and others just stay in place.

This is probably a limitation of the renderer which would take some effort to resolve.

Some higher-end TrueType fonts employ subpixel instructing technique to overcome this issue at small font sizes (i.e. where glyph height doesn't exceed 12-15 pixels). This technique requires a huge amount of work on the affected font, and you would probably buy a retina display long before I get to do it.
Comment 7 Xisco Faulí 2018-09-18 19:57:32 UTC
So, this problem started to happen after David CLM was embedded into LibreOffice in https://cgit.freedesktop.org/libreoffice/core/commit/?id=4099b7628405e0ad16844eb59a916aa56ffa76ad.
Before that, the spacing didn't change.

@Heiko, is it a problem in the font or in LibreOffice ?
Comment 8 Xisco Faulí 2018-09-18 20:02:35 UTC
Reproduced with

* David CLM
* David Libre
* Frank Ruehl CLM
* Frank Ruhl Hofshi

but not with

* Alef
* Miriam CLM
* Miriam Libre
* Miriam Mono CLM
* Nachlieli CLM
* Rubik
Comment 9 Heiko Tietze 2018-09-19 06:05:14 UTC
Pretty sure that's an issue of harfbuzz. Khaled, you are the expert here.
Comment 10 Khaled Hosny 2018-09-19 23:19:53 UTC
No idea what would be going here, but might be rounding errors duo to lack of subpixel glyph positioning.
Comment 11 QA Administrators 2019-09-20 03:05:06 UTC
Dear Idan Miara,

To make sure we're focusing on the bugs that affect our users today, LibreOffice QA is asking bug reporters and confirmers to retest open, confirmed bugs which have not been touched for over a year.

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