Created attachment 172818 [details]
showcase of the wrong selection size indication

SUMMARY
The size of a selection of a rectangular region, indicated by a text positioned somewhere around the selection region, is not correct. It is happening with fractional scaling (125%) on Wayland. I've attached a short clip showcasing the issue.

STEPS TO REPRODUCE
1. Open Spectacle
2.  Select "Rectangular Region" screenshot mode
3.  Make a selection of the entire screen
4. Observe the indicated size in a text box on the bottom of the screen

OBSERVED RESULT
The size doesn't match the monitor's resolution, when the entire screen space of the monitor is selected.

EXPECTED RESULT
The size should match (±1 pixel) the resolution of the display, which can be found in the system settings.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 40 KDE Spin
KDE Plasma Version:  6.1.4
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2

ADDITIONAL INFORMATION
Display: 1920x1080@125%
Graphics Platform: Wayland