Bug 493956

When I alt-tab or click between apps on KWin Wayland on an old computer, sometimes a previous Ctrl-C operation gets delivered as a "c" keystroke to a new app, or the Tab keystroke gets delivered to the previous app (even though Alt was pressed first).

STEPS TO REPRODUCE
1. Boot into KWin Wayland.
2. Start apps and type into them.
3. Alt-tab between them.

OBSERVED RESULT
Randomly keystrokes get delivered to the wrong app.

EXPECTED RESULT
Keystrokes do not get delivered to the wrong app.

SOFTWARE/OS VERSIONS
I have encountered this problem on Fedora 40 on Ivy Bridge iGPU (slow), and Arch Linux on Ryzen CPU and RX 570 GPU (fast). I thought it could be a keyboard switch bounce issue, but I encountered both the erroneous tab insertion and Ctrl-C delivered to the wrong app on both computers with different keyboards (my Ryzen PC's mechanical keyboard has never acted up in this way, in extensive usage on X11 and Windows, and just now I remember I let go of Ctrl+C *before* switching apps but a `c` keystroke was delivered *after* I released the key).

Operating System: Arch Linux 
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.6.0
Qt Version: 6.7.3
Kernel Version: 6.10.10-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 5600X 6-Core Processor
Memory: 15.5 GiB of RAM
Graphics Processor: AMD Radeon RX 570 Series
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: B550M DS3H

ADDITIONAL INFORMATION