broken kerning

[Hadmut Danisch]

Hi,

I am just trying to debug a problem with impress I have after upgrading from 18.04 to 20.04:

On some, not on all slides, text becomes

- unreadable due to negative kerning, i.e. characters are shifted so close together that they are overlapping

- one slide even invisible.

Strangely, the effect occurs
- with libreoffice as a debian package
- with libreoffice as an AppImage downloaded from libreoffice.org
- *but not* with libreoffice as a snap (which doesn't solve the problem because of other problems of accessing local fonts)

Unfortunately, I can't give the slides as an example, they're strictly confidential. But I'm trying to build an example.

Just to bring people together who experience the same problem.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: libreoffice 1:6.4.3-0ubuntu0.20.04.1
ProcVersionSignature: Ubuntu 5.4.0-31.35-generic 5.4.34
Uname: Linux 5.4.0-31-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.2
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: LXQt
Date: Sat May 30 01:43:40 2020
InstallationDate: Installed on 2020-05-27 (2 days ago)
InstallationMedia: Lubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: libreoffice
UpgradeStatus: No upgrade log present (probably fresh install)

[Hadmut Danisch (hadmut)]

Example file:

Slide 1: Vertical negative distance
Slide 2: Horizontal negativ kerning

[Heather Ellsworth (hellsworth)]

Hmm I tried this on a VM that was installed as 18.04 and then upgraded to 20.04 but the test4.odp looked fine in both series.

When you observed the problem, was it in slideshow mode or just the regular edit mode?
After upgrading, did you do an autoremove?

[Hadmut Danisch (hadmut)]

Fresh Install with Lubuntu 20.04, verified with the origial slide show (confidential) and the attachted test file on several machines. Even a completely fresh and untouched install.

Error occurs both in presention/slideshow mode and in edit mode, but in main editor window.

Basically, just start impress with the given file and see it immediately.

However, it was not an upgraded version. But that's a good hint. I'll try a regular Ubuntu installation to see if the problem persists. If you can't see the problem with an upgraded 18.04->20.04 (which is not really a clean test), then it might have something to do with the libraries.

Maybe it's specific to Lubuntu.

[Hadmut Danisch (hadmut)]

I'll attach two screenshots taken from the editor window (Lubuntu 20.04, /usr/bin/libreoffice coming as the regular debian/ubuntu package).

Same looking good and normal on a 18.04 machine.

[Hadmut Danisch (hadmut)]

Second screenshot

[Heather Ellsworth (hellsworth)]

Ah ok I missed the LXQt desktop.. my guess is it is specific to LUbuntu since I tested regular gnome based ubuntu. Ill try it on a fresh LUbuntu system tomorrow.

[Hadmut Danisch (hadmut)]

This morning I've tested a regular ubuntu 20.04,

- freshly installed from iso image (in virtualbox)
- just apt upgrade (where an update for libreoffice came in)
- virtualbox guest additions

and the problem does _not_ occur on that.

So there's some relevant difference between Ubuntu 20.04 and Lubuntu 20.04.

[Heather Ellsworth (hellsworth)]

Hadmut, thanks for testing to confirm my suspicion!

[Hadmut Danisch (hadmut)]

Some progress:

I tried to compare the strace of the process on both Ubuntu and Lubuntu, which was not feasible due to a very different set of Libraries under Ubuntu (gnome) and Lubunt (Qt).

In order to neutralize these differences I started libreoffice with the environment variables completely wiped (except vor PATH and DISPLAY) and the bug does not occur.

So the problem is somehow caused by different environment variables.

[Hadmut Danisch (hadmut)]

I found it.

It's the environment variable

SAL_USE_VCLPLUGIN=qt5

unset it and the bug does not occure.

But I currently don't know what's the meaning of this variable.

[Heather Ellsworth (hellsworth)]

This is very interesting.. I wonder, could you please try setting SAL_USE_VCLPLUGIN=gen when you run libreoffice and tell me if the problem reoccurs?

I ask because there has been another recent bug regarding SAL_USE_VCLPLUGIN: https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/1880416

[Hadmut Danisch (hadmut)]

When setting it to gen, it works well as well.

What's the meaning of setting it to 'gen' ?

[Hadmut Danisch (hadmut)]

The env variable SAL_USE_VCLPLUGIN seems to select which plugin from

/usr/lib/libreoffice/program/libvclplug_*lo.so

to load, maybe some sort of desktop integration driver.

In this case the plugin comes with the package

libreoffice-qt5

which seems to be compiled from the libreoffice source itself.

But still unclear whether this is a problem of this plugin itself or of that many Q5t libraries it is linked against.