Qt5 incorrectly interpret keypresses from remote VNC keyboard

Bug #1831505 reported by Norbert on 2019-06-03
This bug affects 1 person
Affects Status Importance Assigned to Milestone
qtbase-opensource-src (Debian)
Fix Released
qtbase-opensource-src (Ubuntu)

Bug Description

Qt applications incorrectly interpret keyboard input when running over some VNC clients such as TightVNC.

[Test Case]
1. Have Ubuntu 18.04 LTS installed with VNC server
2. Connect to Ubuntu 18.04 LTS from other machine with VNC client
3. Launch any Qt5 based application such as `assistant`, `kate` or `retext`
4. Press keyboard combination on VNC client

Expected results:
all keypresses are recognized successfully

Actual results:
* <Shift> produces `1`
* <Alt> produces `5`
* <`> produces `p`
* <Delete> and <Backspace> are not working
* all letters are messed

[Proposed Fix]
The proposed fix is a backport of two upstream commits: the second being the actual fix, the first one is some refactoring of the code to make it easier to write the second. The commits are:

- https://code.qt.io/cgit/qt/qtbase.git/commit/?id=f8b164e1c37ca901
- https://code.qt.io/cgit/qt/qtbase.git/commit/?id=3edcd9420e3ad661

[Regression Potential]
Most of the new code is triggered only when the keymap is missing rules, models, or layout (i.e. rmlvo_is_incomplete == true). This minimizes the risk of regressions when working with simple X11 server. In any case, the potential regressions will be related to input handling.

[Other Info]
only Qt applications are affected, the GTK-based work as expected (including Chromium from which I write this bug-report)

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: qt5-assistant 5.9.5-0ubuntu1
Uname: Linux 4.4.78-perf+ aarch64
NonfreeKernelModules: wlan exfat
ApportVersion: 2.20.9-0ubuntu7
Architecture: armhf
CurrentDesktop: MATE
Date: Tue Jun 4 00:46:55 2019
 PATH=(custom, no user)
SourcePackage: qttools-opensource-src
UpgradeStatus: No upgrade log present (probably fresh install)

Norbert (nrbrtx) wrote :
Norbert (nrbrtx) wrote :

The CPU architecture is not the problem.
Got the same behavior on amd64 <-> amd64 connection with default settings of TightVNC server.

tags: added: amd64
Norbert (nrbrtx) wrote :
Dmitry Shachnev (mitya57) wrote :

The Debian bug is marked as fixed in Qt 5.11. Can you please check if this bug is present in Disco (which has 5.12)?

Norbert (nrbrtx) on 2019-06-04
tags: added: cosmic
tags: added: xenial
removed: cosmic
Norbert (nrbrtx) wrote :

You are right, bug is fixed in Ubuntu 18.10 (cosmic) and 19.04 (disco).
I can type text in Kate even without XKB.

no longer affects: qttools-opensource-src (Ubuntu)
no longer affects: tightvnc (Ubuntu)
Changed in qtbase-opensource-src (Ubuntu):
status: New → Fix Released
Changed in qtbase-opensource-src (Debian):
status: Unknown → Fix Released
Dmitry Shachnev (mitya57) wrote :

Can you please try packages from https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3731/+packages and see if they fix the issue?

Norbert (nrbrtx) wrote :

Just tested packages from your PPA on amd64. Problem is fixed.
Thank you!

It would be great if you SRU them to bionic.

Does the SRU for 16.04 possible?

Dmitry Shachnev (mitya57) wrote :

It was quite difficult to backport this even to 18.04, as I had to change the code in several places to make it compile.

That was backporting only two releases back (5.11 → 5.9). 16.04 has 5.5 so that sounds impossible, however patches are welcome.

description: updated
Łukasz Zemczak (sil2100) wrote :

The two patches seem a bit big (with all that refactoring), but I guess I didn't see any follow up changes to this code upstream. Also, with the regression potential well defined, I'm inclined to accept it.

Changed in qtbase-opensource-src (Ubuntu Bionic):
status: New → Fix Committed
tags: added: verification-needed verification-needed-bionic

Hello Norbert, or anyone else affected,

Accepted qtbase-opensource-src into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/qtbase-opensource-src/5.9.5+dfsg-0ubuntu2.3 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-bionic to verification-done-bionic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-bionic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

All autopkgtests for the newly accepted qtbase-opensource-src (5.9.5+dfsg-0ubuntu2.3) for bionic have finished running.
There have been regressions in tests triggered by the package. Please visit the sru report page and investigate the failures.


Norbert (nrbrtx) wrote :

Packages from bionic-proposed fix the issue.

Dmitry Shachnev (mitya57) wrote :

> Packages from bionic-proposed fix the issue.

Thanks, marking as verified then.

tags: added: verification-done verification-done-bionic
removed: verification-needed verification-needed-bionic
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