Bug 94737 - Poor subpixel rendering on Linux
Summary: Poor subpixel rendering on Linux
Status: RESOLVED WORKSFORME
Alias: None
Product: LibreOffice
Classification: Unclassified
Component: graphics stack (show other bugs)
Version:
(earliest affected)
5.0.1.2 release
Hardware: x86-64 (AMD64) Linux (All)
: medium minor
Assignee: Not Assigned
URL:
Whiteboard:
Keywords: regression
Depends on:
Blocks:
 
Reported: 2015-10-03 20:18 UTC by S.
Modified: 2018-07-12 12:41 UTC (History)
3 users (show)

See Also:
Crash report or crash signature:


Attachments
test document (17.18 KB, application/vnd.oasis.opendocument.spreadsheet)
2015-10-03 20:18 UTC, S.
Details
5.0.1 mixed hinting at 120% zoom (321.42 KB, image/jpeg)
2015-10-03 20:20 UTC, S.
Details
4.4.5 good uniform hinting at 120% zoom (341.48 KB, image/jpeg)
2015-10-03 20:21 UTC, S.
Details
no hinting at 85% zoom on 5.0.1 (322.61 KB, image/jpeg)
2015-10-03 20:21 UTC, S.
Details
correct hinting at 85% zoom on 4.4.5 (357.94 KB, image/jpeg)
2015-10-03 20:22 UTC, S.
Details
fresh 85% (130.76 KB, image/png)
2015-10-05 01:31 UTC, S.
Details
fresh 95% (124.62 KB, image/png)
2015-10-05 01:31 UTC, S.
Details
fresh 100% (131.45 KB, image/png)
2015-10-05 01:32 UTC, S.
Details
fresh 110% (123.75 KB, image/png)
2015-10-05 01:32 UTC, S.
Details
4.4.5 85% good rendering PNG (127.90 KB, image/png)
2015-10-05 04:05 UTC, S.
Details
4.4.5 90% good rendering PNG (125.60 KB, image/png)
2015-10-05 04:05 UTC, S.
Details
4.4.5 110% good rendering PNG (121.19 KB, image/png)
2015-10-05 04:06 UTC, S.
Details
screenshot 85% zoom on master - Ubuntu Linux (619.94 KB, image/png)
2016-02-20 04:35 UTC, Chris Sherlock
Details
screenshot 110% zoom on master - Ubuntu Linux (621.88 KB, image/png)
2016-02-20 04:36 UTC, Chris Sherlock
Details

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Description S. 2015-10-03 20:18:34 UTC
Created attachment 119244 [details]
test document

Hello,

I am attaching screenshots of a document opened in LibreOffice 5.0.1 compared to the same document opened in 4.4.5 on the same Manjaro (derived from Arch) Linux system. The document uses the Ubuntu font family, and the subpixel hinting looks very good on 4.4.5 but doesn't appear to work at all in 5.0.1 at lower zoom levels. Then at 120% zoom, it still looks excellent and uniformly rendered on 4.4.5, but on 5.0.1 it starts to show hinting on some of the larger font sizes but not on smaller fonts, resulting in an ugly mixed-bag display. This same semi-hinted rendering is visible at several different zoom levels as you slide up and down.

I already played around with the Options -> View -> antialiasing settings, but it makes no difference. I also tried installing the -ubuntu font rendering packages into Arch (sorry no screenshots) but it still resulted in mixed rendering similar to my 120% zoom screenshot.

Thanks for looking into this.
Comment 1 S. 2015-10-03 20:20:18 UTC
Created attachment 119245 [details]
5.0.1 mixed hinting at 120% zoom
Comment 2 S. 2015-10-03 20:21:06 UTC
Created attachment 119246 [details]
4.4.5 good uniform hinting at 120% zoom
Comment 3 S. 2015-10-03 20:21:43 UTC
Created attachment 119247 [details]
no hinting at 85% zoom on 5.0.1
Comment 4 S. 2015-10-03 20:22:41 UTC
Created attachment 119248 [details]
correct hinting at 85% zoom on 4.4.5
Comment 5 tommy27 2015-10-04 06:11:13 UTC
edited summary notes and moved regression from summary to keywords

please tell the model of your graphic card as well
Comment 6 S. 2015-10-04 12:34:45 UTC
Thanks. Intel i915 graphics.

I should mention that the bug is much more noticeable on the original document, which of course contained other characters besides xxx :)
Comment 7 Adolfo Jayme Barrientos 2015-10-04 13:11:13 UTC
JPEG screenshots are useless to look for artifacts.
Comment 8 S. 2015-10-04 13:16:59 UTC
Sorry for the screenshots, they were originally PNG then I cropped them and accidentally saved them as JPG. But it's really quite obvious, the characters than look "thicker" and lighter are correctly hinted, and the "thinner" lighter letters are not correctly hinted.
Comment 9 tommy27 2015-10-04 14:08:02 UTC
please post a PNG screenshot then
Comment 10 S. 2015-10-05 01:31:36 UTC
Created attachment 119288 [details]
fresh 85%
Comment 11 S. 2015-10-05 01:31:58 UTC
Created attachment 119289 [details]
fresh 95%
Comment 12 S. 2015-10-05 01:32:37 UTC
Created attachment 119290 [details]
fresh 100%
Comment 13 S. 2015-10-05 01:32:56 UTC
Created attachment 119291 [details]
fresh 110%
Comment 14 S. 2015-10-05 04:05:25 UTC
Created attachment 119296 [details]
4.4.5 85% good rendering PNG
Comment 15 S. 2015-10-05 04:05:45 UTC
Created attachment 119297 [details]
4.4.5 90% good rendering PNG
Comment 16 S. 2015-10-05 04:06:09 UTC
Created attachment 119298 [details]
4.4.5 110% good rendering PNG
Comment 17 S. 2015-10-05 20:01:31 UTC
Even stranger, the font rendering seems to be affected by what interface LibO is using. When I start LibreOffice like...

SAL_USE_VCLPLUGIN=gtk3 lowriter

... it produces the bad rendering I explained here.

But when I start it like...

SAL_USE_VCLPLUGIN=gtk lowriter

... the rendering is good, even in LibreOffice 5.0.
Comment 18 Buovjaga 2015-10-09 08:17:24 UTC
Repro on Kubuntu 15.04 64-bit, LibO 5.0.2.2 (KDE integration).
I get the ugly result with 85% zoom no matter what vcl export I use.
Comment 19 S. 2015-10-09 13:37:28 UTC
As for the importance of "minor" assigned to this bug, I think that for those of us who spend the entire day or even longer staring at a LibreOffice screen, lack of good font rendering is hardly a "minor" concern. :)
Comment 20 Buovjaga 2015-10-09 14:10:58 UTC
(In reply to S. from comment #19)
> As for the importance of "minor" assigned to this bug, I think that for
> those of us who spend the entire day or even longer staring at a LibreOffice
> screen, lack of good font rendering is hardly a "minor" concern. :)

Here is the flowchart for determining those: https://wiki.documentfoundation.org/images/0/06/Prioritizing_Bugs_Flowchart.jpg
In general it is quite hard to prioritize and determine severity. That is why we restrict the fields from regular users.

We do need new QA people desperately as the report flow is not slowing down. Please consider contributing: https://wiki.documentfoundation.org/QA/Triage_For_Beginners
Comment 21 Robinson Tryon (qubit) 2015-12-14 05:32:47 UTC Comment hidden (obsolete)
Comment 22 Chris Sherlock 2016-02-16 05:57:03 UTC
OS X build on slightly old copy of master doesn't actually seem to be picking up the Ubuntu font on my workstation... investigating.
Comment 23 Chris Sherlock 2016-02-16 08:27:17 UTC
OK, I'm grabbing the bibisect tar file. Will see where this started to occur.
Comment 24 Chris Sherlock 2016-02-20 04:27:51 UTC
Sorry this is taking so long, I'm having some bibisect problems.
Comment 25 Chris Sherlock 2016-02-20 04:35:36 UTC
Created attachment 122811 [details]
screenshot 85% zoom on master - Ubuntu Linux
Comment 26 Chris Sherlock 2016-02-20 04:36:21 UTC
Created attachment 122812 [details]
screenshot 110% zoom on master - Ubuntu Linux
Comment 27 S. 2016-02-20 04:44:29 UTC
Thanks a lot Chris for looking into this!
Comment 28 Chris Sherlock 2016-02-20 04:47:11 UTC
Beluga, S. - I'm running this in a VM that doesn't have GL acceleration and I'm not seeing the problem you are evidentally seeing. I've tried with GTK, GTK3 and KDE, fonts look fine. 

Unfortunately I don't have access to a Linux system that can use accelerated OpenGL graphics. 

Perhaps someone else could bibisect this one?
Comment 29 Chris Sherlock 2016-02-20 04:49:20 UTC
S. - any chance you could bibisect this?

Unfortunately the tar file is massive, but it would help to pinpoint where things started going wrong. 

https://wiki.documentfoundation.org/QA/Bibisect/Linux
Comment 30 Buovjaga 2016-03-12 16:57:18 UTC
I started bibisecting this, but the problem is already in 4.3 alpha (oldest of 44max repo). I did it under Ubuntu 16.04.
Comment 31 QA Administrators 2017-05-22 13:19:31 UTC Comment hidden (obsolete)
Comment 32 S. 2017-05-22 15:13:28 UTC
I now use LibreOffice 5.3 on openSUSE Tumbleweed, and this bug doesn't appear to be present, so I'm marking it as fixed. But if any Arch/Manjaro users are still seeing this problem feel free to jump in.
Comment 33 Buovjaga 2017-05-22 15:33:20 UTC
I'm still seeing this. Note that this is not restricted to Arch: in 2015 I reproduced with Ubuntu.
If I double-click in a cell with the bad kerning and then defocus, it gets correct. Save & reload brings the badness back.

Arch Linux 64-bit, KDE Plasma 5
Version: 5.5.0.0.alpha0+
Build ID: 6b5fc059543c16759abd5eec2576b5b68e96883a
CPU threads: 8; OS: Linux 4.10; UI render: default; VCL: kde4; 
Locale: fi-FI (fi_FI.UTF-8); Calc: group
Built on May 21st 2017
Comment 34 QA Administrators 2018-05-23 02:35:14 UTC Comment hidden (obsolete)
Comment 35 Buovjaga 2018-07-12 12:41:49 UTC
(In reply to S. from comment #14)
> Created attachment 119296 [details]
> 4.4.5 85% good rendering PNG

I now get this result with master. Tried gen & gtk2 backends in addition to gtk3 just in case it would make a difference.

Closing as WFM.

Arch Linux 64-bit
Version: 6.2.0.0.alpha0+
Build ID: bd394492c165d27c96a44495d9ca694a242acb8f
CPU threads: 8; OS: Linux 4.17; UI render: default; VCL: gtk3; 
Locale: fi-FI (fi_FI.UTF-8); Calc: group threaded
Built on July 11th 2018