Bug 2403284 - Touchscreen mapping doesn't adjust when screen resolution changes from 16:10 to 16:9
Summary: Touchscreen mapping doesn't adjust when screen resolution changes from 16:10 ...
Keywords:
Status: CLOSED DEFERRED
Alias: None
Product: Fedora
Classification: Fedora
Component: gnome-shell
Version: 42
Hardware: x86_64
OS: Linux
unspecified
high
Target Milestone: ---
Assignee: GNOME SIG Unassigned
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2025-10-11 14:37 UTC by otheos
Modified: 2025-10-11 20:03 UTC (History)
5 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed: 2025-10-11 20:03:09 UTC
Type: ---
Embargoed:


Attachments (Terms of Use)

Description otheos 2025-10-11 14:37:24 UTC
This has been tested on a ThinkBook 14 2-in-1 and a ThinkPad X13 Yoga Gen 3. 
Both laptops have a touchscreen (with pen input) and run at 1920x1200.
At the native resolution the touchscreen is mapped to the screen perfectly, so the touch appears below the fingertip.

Changing the resolution to 1920x1080 (16:9), as is sometimes needed to mirror with external screens/projectors, breaks the mapping of the touchscreen.

On the centre line (half way up), the mapping stays perfect. Above the centre line the touch is lower than the the fingertip and below the centre line the touch is above the fingertip. The distance between fingertip and touch increases as you move away from the centre line.

The mapping of the touchscreen either stays on 1920x1200 or it is wrong when at 1920x1080.

In general, any 16:10 resolution (eg 1680x1050) works fine, and any 16:9 resolution (eg 1600x900) has the issue.

This is obviously an issue as once an external screen is connected that cannot do 1920x1200 and needs a 16:9 resolution to maintain its geometry, the touch control of the laptop(s) is finicky at best. 

The pen input is also affected, and it's impossible to use the pen to write.

Reproducible: Always

Steps to Reproduce:
1. Set resolution to any 16:9 from 16:10 (from 1920:1200 to 1920:1080)
2. Try to move windows by grabbing the header bar.  The higher above the centre line the header bar is, the further up your fingertip must be from it to grab it. 
Actual Results:
The fingertip and the touch point on the desktop are off. The pen tip and the line drawn are off. They are perfectly aligned on the centre line of the screen, but once you are above the centre line (closer to the top of the screen) the line appears below the pen tip (and touch below the finger tip), and if you go below the centre line (close to the bottom of the screen), the line appears above the pen tip (and the touch also above the finger tip).

Expected Results:
The line appears at the tip of the pen everywhere on the screen. 

Additional Information:
I've played with some udev rules and I can change the mapping when at 1080p but I cannot find how to fix the offset as it is not constant.

Comment 1 Fedora Admin user for bugzilla script actions 2025-10-11 14:37:31 UTC
Bug reports for this component on Red Hat Bugzilla are not actively monitored. Please consider reporting your issue directly to GNOME at https://gitlab.gnome.org/GNOME/ to improve the chances that your issue will be resolved. This issue should only be kept open if it:

1. Relates to Fedora packaging or integration with other Fedora components
2. Is required for Fedora release processes, such as blocker bugs and freeze exceptions

If this issue isn't needed for either of these two reasons, please:

 * create an issue with GNOME
 * add a link to the GNOME issue here
 * close this issue as CLOSED/UPSTREAM

Thank you!

Comment 2 otheos 2025-10-11 20:03:09 UTC
(In reply to Fedora Admin user for bugzilla script actions from comment #1)
> Bug reports for this component on Red Hat Bugzilla are not actively
> monitored. Please consider reporting your issue directly to GNOME at
> https://gitlab.gnome.org/GNOME/ to improve the chances that your issue will
> be resolved. This issue should only be kept open if it:
> 
> 1. Relates to Fedora packaging or integration with other Fedora components
> 2. Is required for Fedora release processes, such as blocker bugs and freeze
> exceptions
> 
> If this issue isn't needed for either of these two reasons, please:
> 
>  * create an issue with GNOME
>  * add a link to the GNOME issue here
>  * close this issue as CLOSED/UPSTREAM
> 
> Thank you!

Thank you

I have tested this on Ubuntu 25.04 and it is indeed Gnome related. I have now filed a bug at Gnome. I think this bug can be archived.

Thank you again.


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