Created attachment 185928 [details]
Error banner on the gui

SUMMARY
Trying to capture any WINDOWED steam proton game window via spectacle's Active Window capture method results in the below error - while the shortcut Meta+PrtScr works normally.

FULLSCREENED proton games either screenshot the below window or give the same below error.

An error occurred while taking a screenshot.
KWin screenshot request failed:
Invalid window requested
Potentially relevant information:
- Method: CaptureActiveWindow
- Method specific arguments: QMap(("include-shadow", QVariant(bool, false))("native-resolution", QVariant(bool, true)))

STEPS TO REPRODUCE
1. Start any steam proton game
2. Switch to windowed mode
3. Restart the game
4. Press PrtScr
5. From the bottom toolbar press New Screenshot->Active Window
6. Spectacle GUI pops up with kwin screenshot request failed banner

OBSERVED RESULT
Unable to screenshot steam proton games via active window method

EXPECTED RESULT
Able to screenshot steam proton games via active window method

SOFTWARE/OS VERSIONS
kinfo of both below machines where it happens:

Operating System: Arch Linux
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0
Kernel Version: 6.17.3-zen2-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ i5-8250U CPU @ 1.60GHz
Memory: 40 GiB of RAM (38.9 GiB usable)
Graphics Processor: Intel® UHD Graphics 620

Operating System: Manjaro Linux 
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.18.0
Qt Version: 6.10.0
Kernel Version: 6.18.0-rc0-3-MANJARO (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5800X3D 8-Core Processor
Memory: 128 GiB of RAM (125.4 GiB usable)
Graphics Processor: AMD Radeon RX 7900 XTX

ADDITIONAL INFORMATION
- I also tried aur/spectacle-git:6.5.0.r4.g8a7d4fb-1 but it happens there too.
- On the Arch machine it also happened pre-update with Plasma: 6.4.4, Frameworks: 6.17, Qt: 6.9.2
- Tried different proton versions.
- On the desktop pc tried unplugging multi-monitors.
- NATIVE WINDOWED steam games work
    tested: teeworlds, ballisticng, amnesia, slipstream
- NATIVE FULLSCREEN steam games capture the below window without an error
    tested: teeworlds, ballisticng, amnesia, slipstream

Looking at the kwin debug console the proton game window to be captured loses active status as soon as PrtScr is pressed and the "When launching Spectacle: Take Rectangular screenshot" overlay spawns. However the same "losing active status" also happens with system apps like Kate where the Active Window capture method still works normally.

Related and possibly duplicate of this bug:
https://bugs.kde.org/show_bug.cgi?id=501593#c9