[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Nate Graham]

https://bugs.kde.org/show_bug.cgi?id=358472

Nate Graham  changed:

   What|Removed |Added

 Resolution|--- |FIXED
 Status|REOPENED|RESOLVED

--- Comment #35 from Nate Graham  ---
(In reply to idmresettrial from comment #34)
> I think I've solved the problem by switching the touchpad driver from
> synaptic to libinput.
> 
> You can close the bug if you want.

Your issue is more likely https://bugs.kde.org/show_bug.cgi?id=393202

Seems like the original issue is gone now, so I'll close this.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[idmresettrial]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #34 from idmresettrial  ---
I think I've solved the problem by switching the touchpad driver from synaptic
to libinput.

You can close the bug if you want.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[idmresettrial]

https://bugs.kde.org/show_bug.cgi?id=358472

idmresettrial  changed:

   What|Removed |Added

Version|5.5.3   |5.13.0
   Platform|Fedora RPMs |openSUSE RPMs

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[idmresettrial]

https://bugs.kde.org/show_bug.cgi?id=358472

idmresettrial  changed:

   What|Removed |Added

 CC||idmresettr...@gmail.com
 Status|RESOLVED|REOPENED
 Resolution|UPSTREAM|---

--- Comment #33 from idmresettrial  ---
Still happens with Qt 5.11 on openSUSE Tumbleweed 20180625



It happens with the Discover widget, Folder widget but not with Falkon,
Konsole, Dolphin.

A QML bug?

Screenshot: https://i.imgur.com/bXDALSx.png

The text will render correctly if I continue scrolling up/down some more
pixels.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Nate Graham]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #32 from Nate Graham  ---
Fantastic news!

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[akm]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #31 from akm  ---
hi,
it just reached Tumbleweed it seems as I am on libQT 5.10.0-3 and issue is gone
as far as I can tell. 

Thank you

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[David Edmundson]

https://bugs.kde.org/show_bug.cgi?id=358472

David Edmundson  changed:

   What|Removed |Added

 Status|CONFIRMED   |RESOLVED
 Resolution|--- |UPSTREAM

--- Comment #30 from David Edmundson  ---
A fix is now in Qt in the 5.9 branch, but I don't think targetting 5.9.4

See https://codereview.qt-project.org/#/c/212398/

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[akm]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #29 from akm  ---
Hello Lorenzo

Am on Tumbleweed, it has xf86-input-evdev installed.
did a diff between the already installed /etc/X11/xorg.conf.d/10-evdev.conf and
yours and they are a 100% match.
So at least on Tumbleweed it's not a work around.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Lorenzo Murarotto]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #28 from Lorenzo Murarotto  ---
Found a workaround (for arch linux):
1. Install xf86-input-evdev
2. Create file /etc/X11/xorg.conf.d/10-evdev.conf (Delete existing if needed).
3. Put https://pastebin.com/Y5cePdTj in said file.
4. Reboot.

Tell me if it worked :)

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[David Edmundson]

https://bugs.kde.org/show_bug.cgi?id=358472

David Edmundson  changed:

   What|Removed |Added

 CC||lnz...@gmail.com

--- Comment #27 from David Edmundson  ---
*** Bug 388701 has been marked as a duplicate of this bug. ***

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Nate Graham]

https://bugs.kde.org/show_bug.cgi?id=358472

Nate Graham  changed:

   What|Removed |Added

 CC||pointedst...@zoho.com

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Dr . Chapatin]

https://bugs.kde.org/show_bug.cgi?id=358472

Dr. Chapatin  changed:

   What|Removed |Added

 CC||yy...@gmx.com

--- Comment #26 from Dr. Chapatin  ---
Created attachment 105735
  --> https://bugs.kde.org/attachment.cgi?id=105735=edit
fonts corrupted in desktop themes kcm

Fonts corrupted in desktop themes kcm, see the screenshot.
I use Arch, plasma 5.9.5.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[David Edmundson]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #24 from David Edmundson  ---
Upstream bug report: https://bugreports.qt.io/browse/QTBUG-59261

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[David Edmundson]

https://bugs.kde.org/show_bug.cgi?id=358472

David Edmundson  changed:

   What|Removed |Added

 CC||andy...@mail.ru

--- Comment #25 from David Edmundson  ---
*** Bug 380248 has been marked as a duplicate of this bug. ***

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Alex Tucker]

https://bugs.kde.org/show_bug.cgi?id=358472

Alex Tucker  changed:

   What|Removed |Added

 CC||a...@floop.org.uk

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[David Edmundson]

https://bugs.kde.org/show_bug.cgi?id=358472

David Edmundson  changed:

   What|Removed |Added

 Ever confirmed|0   |1
 Status|UNCONFIRMED |CONFIRMED

--- Comment #23 from David Edmundson  ---
This is a combo bug in both Qt's XCB backend and ScrollArea in QtQuickControls

scrolling has two modes, moving by n pixels or by n "ticks".
In QWheelEvent terms:
 - pixelDelta and angleDelta

A libinput change has meant that Qt's detection of "is it a scroll wheel or
not" is broken. 
I think libinput seems to trying to artificially say how far things should
scroll at an input level rather than it being up to the application.

In QXcbConnection::xi2HandleScrollEvent scrollingDevice.verticalIncrement is 15
.

This matches what I see in xinput list which shows:
Class originated from: 11. Type: XIScrollClass
Scroll info for Valuator 2
  type: 2 (horizontal)
  increment: 15.00
  flags: 0x0

We then go into the

  // We do not set "pixel" delta if it is only measured in ticks.
if (scrollingDevice.horizontalIncrement > 1)
rawDelta.setX(delta);



In most Qt code this isn't a problem. Either pixel delta is ignored or it looks
about right anyway

In QtQuickControls QtQuickWheelArea we have a huge bug; as we now have valid
pixelDelta we go into a different code path that ignores the user scrollspeed.
It then randomly divides things by 2 to match some OS X behaviour.

This is what leads to things being slow and corrupted fonts. 


I'll probably have to close this as upstream once I file a bug report there.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #22 from Matthias Dahl  ---
(In reply to Dmitry Belyakin from comment #21)

> Could it be related to libinput?

The problem is with Qt -- and it has been located (= the commit that caused it
and why it is happening). I have provided a patch as a stepping-stone (so to
speak) to a final solution but thus far, I got no reaction at all on the Qt bug
tracker. Personally, I use my patch without any problems but it is _definitely_
not a final solution. I am planning on revisiting this issue once I have some
more free time on my hands -- and if it hasn't been fixed meanwhile.

It is really a pity that this hasn't been addressed yet and remains an open
issue, even though the cause has been located and a first patch was provided.
:-(

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Dmitry Belyakin]

https://bugs.kde.org/show_bug.cgi?id=358472

Dmitry Belyakin  changed:

   What|Removed |Added

 CC||d-belya...@ya.ru

--- Comment #21 from Dmitry Belyakin  ---
Could it be related to libinput?
I found this post:
https://forum.manjaro.org/t/kde-bad-font-rendering-when-scrolling/5175/2 but I
didn't try suggested solution

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Christoph Feck]

https://bugs.kde.org/show_bug.cgi?id=358472

Christoph Feck  changed:

   What|Removed |Added

 CC||k...@web.de

--- Comment #20 from Christoph Feck  ---
*** Bug 375091 has been marked as a duplicate of this bug. ***

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Ilya Bizyaev]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #19 from Ilya Bizyaev  ---
For some reason, this bug is not present in Kubuntu although is has the same Qt
version.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[akm]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #18 from akm  ---
(In reply to Ilya Bizyaev from comment #17)
> Same problem here.
> Fresh install of openSUSE Leap 42.2.

see the link from Matthias: https://bugreports.qt.io/browse/QTBUG-55638
it needs to be fixed by QT it seems.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Ilya Bizyaev]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #17 from Ilya Bizyaev  ---
Same problem here.
Fresh install of openSUSE Leap 42.2.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Ilya Bizyaev]

https://bugs.kde.org/show_bug.cgi?id=358472

Ilya Bizyaev  changed:

   What|Removed |Added

 CC||bizyaev.g...@yandex.ru

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Christian Stadelmann via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

Christian Stadelmann  changed:

   What|Removed |Added

URL||https://bugreports.qt.io/br
   ||owse/QTBUG-55638

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #15 from Matthias Dahl  ---
(In reply to akm from comment #14)
> can also confirm this on Thumbleweed, took me a while to find this bug
> report, just glad its not only me getting irritated by it :)

Thanks for reporting back here. It would be awesome if you could hop over to
the Qt bug, give that qml minimal working example a try I posted there and
report your findings as well as some system stats there as well. You can try
the mwe by simply opening it with "qmlscene". Thanks so much in advance...

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[akm via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

akm  changed:

   What|Removed |Added

 CC||a.vank...@chello.nl

--- Comment #14 from akm  ---
can also confirm this on Thumbleweed, took me a while to find this bug report,
just glad its not only me getting irritated by it :)

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #13 from Matthias Dahl  ---
A quick grep revealed that apart from KWIN, a few other places still use
ScrollView and would need adaptation as well to set the Flickable's
pixelAligned=true to avoid  the corruption.

All things said though, this should not cause such a severe corruption after
all. I have tried all morning long to debug what is going on in Qt but right
now all I got is a head that is about to lift off from my shoulders. I hope the
Qt devs do consider the bug report and won't leave it to rot.

By the way, could someone set this to confirmed?

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Kai Uwe Broulik via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

Kai Uwe Broulik  changed:

   What|Removed |Added

 CC||k...@privat.broulik.de

--- Comment #12 from Kai Uwe Broulik  ---
We have a dedicated Plasma ScrollArea used everywhere where we could just
enable pixel alignment globally.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #11 from Matthias Dahl  ---
Like expected, this issue can be seen in other places as well. Pretty much
everywhere where something inherited from Flickable is issued, like the Widgets
browser (via "Add widgets...").

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #10 from Matthias Dahl  ---
Created attachment 100867
  --> https://bugs.kde.org/attachment.cgi?id=100867=edit
severe corruption in kickoff

Here another example screenshot where the corruption was more severe... which
is actually also the typical case. The corruption in the unscrollable area
below (Computer, Leave, ...) won't be fixed by scrolling or re-opening the
menu. Only "restarting" kickoff will fix it.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #9 from Matthias Dahl  ---
Since this also belongs here, I am copying and pasting from the Qt bug report
where I just added the following:

Ok, here what I have been able to debug:

Everything that uses something inherited from Flickable (like ListView) will
expose the issue. Scrolling will result in fractional positions for the content
which will cause (severe) font corruption. Since Flickable defaults
pixelAligned to false since its inception, those fractional positions are not
rounded. Switching pixelAligned to true, fixes the corruption entirely, like
expected. Most instances in KDE leave pixelAligned at its default, thus the
widespread problem.

As far as I know, subpixel positioning is currently only supported on Mac OS X.
Questions remains, how are those fractional positions handled on other
platforms – especially Linux? It seems like something is going terribly wrong
and corrupting the glyph cache.

Either way, I don't think fractional positions should result in a corrupted
type face whatsoever... or any kind of corruption.

Is there anything else I can do to further debug this and be of any help?

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #8 from Matthias Dahl  ---
Like expected, a minimal Qt example was asked for in the Qt bug report.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #7 from Matthias Dahl  ---
Meanwhile I have also tested this with a fresh OpenSuSE Tumbleweed Live iso in
a virtual machine and the issue is also 100% reproducible there as well.

I have also taken the liberty to report this upstream:
https://bugreports.qt.io/browse/QTBUG-55638

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #6 from Matthias Dahl  ---
I forgot to mention: I also tested this with Qt's 5.6 git branch as of today --
the corruption is absolutely the same, even though a lot of font and scrolling
related fixes went in after 5.6.1.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #5 from Matthias Dahl  ---
Created attachment 100847
  --> https://bugs.kde.org/attachment.cgi?id=100847=edit
font corruption after one wheel unit in application launcher

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #4 from Matthias Dahl  ---
Created attachment 100846
  --> https://bugs.kde.org/attachment.cgi?id=100846=edit
font corruption after one wheel unit in kcm desktop effects

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #3 from Matthias Dahl  ---
I can confirm this issue as well. It has been long-standing, unfortunately.

I will attach two more screenshots which show it rather prominently -- one from
the application launcher and one from the desktop effects kcm.

My experience is that this can only be triggered when scrolled via mouse wheel
and that way it is 100% reproducible and happens all the time.

For example:

1) Open the desktop effects kcm.
2) Scroll the list of effects one wheel unit down
--> Font corruption happens

If you scroll another wheel unit, everything looks fine again. Another wheel
unit, and the font is garbled again. And so forth.

I have tried to narrow this down but so far have failed. If there is anything I
can do at all to help track this bug down, please let me know.

I am seeing this on a fresh Gentoo x86_64 system w/ frameworks 5.25.0, plasma
5.7.4, Qt 5.6.1 and freetype 2.6.5. Xorg uses nvidia driver 370.23. KWIN
Compositor is using OpenGL 3.1. But neither of those latter ones make any
difference.

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Matthias Dahl via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

Matthias Dahl  changed:

   What|Removed |Added

 CC||ua_bugz_kde@binary-island.e
   ||u

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Christian Stadelmann via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #1 from Christian Stadelmann  ---
Created attachment 96810
  --> https://bugs.kde.org/attachment.cgi?id=96810=edit
software updates widget with corrupted fonts

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[plasmashell] [Bug 358472] plasma widgets: fonts get corrupted on scrolling vertically

[Christian Stadelmann via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=358472

--- Comment #2 from Christian Stadelmann  ---
Created attachment 96811
  --> https://bugs.kde.org/attachment.cgi?id=96811=edit
device manager with corrupted fonts

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