https://bugs.kde.org/show_bug.cgi?id=487596
Bug ID: 487596
Summary: Screenshot region selection broken with fractional
scaling on multi-monitor setups (X11)
Classification: Applications
Product: Spectacle
Version: 23.08.5
Platform: Ubuntu
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: General
Assignee: noaha...@gmail.com
Reporter: m...@fsfe.org
CC: k...@david-redondo.de
Target Milestone: ---
SUMMARY
When Spectacle is used to select a rectangular region (i.e. executing
"spectacle --region") on setups using multiple monitors and fractional scaling
(on X11), the screen image where the rectangular selection happens shows a
distorted and shifted image of the screen.
This makes it impossible to select the correct region as the displayed image
does not match the actual screen contents.
STEPS TO REPRODUCE
1. Attach a secondary monitor.
2. Configure monitors to be side by side (see below).
3. In System Settings set global scaling to 125%.
4. Run "spectacle --region".
Excerpt from "~/.config/kdeglobals":
```
[KScreen]
ScaleFactor=1.25
ScreenScaleFactors=eDP-1=1.25;DP-1=1.25;DP-2=1.25;DP-3=1.25;
```
Example screen alignment as reported by `xrandr`:
```
eDP-1 connected 1600x900+0+180
DP-1 connected primary 1920x1080+1600+0
```
OBSERVED RESULT
The surface where the rectangular selection box is drawn on does not represent
the actual screen contents, it displays a distorted image of contents from both
screens where areas of the screens are repeated or shifted around.
This mainly affects the primary monitory but if the secondary monitor does not
have the same resolution as the primary one, it will also show a distorted
image.
After the screenshot has been taken it seems that the actual recording does
match the screen contents, only the preview is misrepresenting the state which
makes it almost impossible to select the correct region.
EXPECTED RESULT
The screen image during rectangular region selection should represent the
actual contents of screens.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kubuntu 24.04
KDE Plasma Version: 5.27.11
KDE Frameworks Version: 5.115.0
Qt Version: 5.15.13
Platform: X11
ADDITIONAL INFORMATION
Note 1
The issue can be reproduced using VirtualBox easily utilizing its functionality
to attach a second virtual display (if guest additions are installed) and
reproducing a screen arrangement as described above accordingly.
Note 2
The issue is not exclusive to Kubuntu.
It also affects the following NixOS configuration:
Linux/KDE Plasma: NixOS 23.11
KDE Plasma Version: 5.27.11
KDE Frameworks Version: 5.113.0
Qt Version: 5.15.12
Platform: X11
Note 3
LXQt's screenshot tool ("screengrab") seems to suffer from similar issues and
its author suspects it to be a Qt bug related to screen coordinates:
https://github.com/lxqt/screengrab/issues/211
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