Bug 474954

SUMMARY
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Spectacle's box-select tool is designed to show you the underlying display so that you can select a region of it to save or copy to the clipboard. In my current setup, this interface is bugged, such that on my primary monitor about the left one-third of the underlying display is shown correctly, but the same image is repeated starting about one-third of the way across the screen. This results in two copies of the left one-third of the underlying display visible simultaneously: when in the box-select tool, the left one-third of the screen or so is the left one-third of the underlying display, the middle one-third is the left one-third of the underlying display repeated again, and the right one-third is the middle one-third of the underlying display.

Notably, this bug does not affect the image that is taken by the tool; if I select an area of the bugged offset two-thirds, the resulting image is the correct area of the underlying display. This means that taking screenshots is incredibly unwieldy unless they're entirely within the correct left one-third of the display - in order to select the correct area to produce the image I want, I have to estimate where on the screen is the correct position based on whatever cues I can gather from what is displayed - using the correct left one-third and/or mentally correcting for the shifted duplicated screen area.

This seems to be the result of my multiple-monitor setup; when I have one monitor connected, Spectacle behaves correctly. My current setup involves a TV set up as placed to the left of my primary monitor, and notably Spectacle *also* behaves correctly on the TV when the TV is on and connected. The bug only occurs on my primary monitor when the secondary display is also connected.
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STEPS TO REPRODUCE
1. Connect two monitors to your system, such that the right of the pair is considered primary
2. Open the box-select tool via either the hotkey or the button in Spectacle's dedicated UI
3. Observe that, on the primary right-side monitor, suddenly the right two thirds of the underlying display are hidden behind a duplicate of the left two thirds
4. Take a screenshot of anywhere in the duplicated area, observing that the resulting screenshot is not of the duplicate that was visible when you took it, but instead correctly represents the area of the unmodified display you selected

OBSERVED RESULT
On the primary monitor, the box-select tool shows an incorrect representation of the display area you're trying to select from

EXPECTED RESULT
The box-select tool's interface should simply reproduce the underlying display exactly on all displays

SOFTWARE/OS VERSIONS
Manjaro kernel version: 6.1.53-1-MANJARO (64 bit)
KDE Plasma Version: 5.27.8
KDE Frameworks Version: 5.110.0
Qt Version: 5.15.10

ADDITIONAL INFORMATION