SUMMARY
Resizing any window with Plastik style on X11 uses more and more GPU memory. It doesn't happen with Oxygen and Breeze styles. The GPU memory can be freed on kwin_x11 restart. I can observe this problem on Radeon (Mesa) and NVIDIA with proprietary drivers.


STEPS TO REPRODUCE
1. Run X11 session.
2. Set Plastik KWin style.
3. Resize any window for a long time (e.g 1 minute).

OBSERVED RESULT
GPU memory usage increases on every window resize.

EXPECTED RESULT
GPU memory usage doesn't increase on window resize.

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.24.2
KDE Frameworks Version:  5.91.0
Qt Version: 5.12.2
Mesa: 21.3.6
Nvidia: 510.54

ADDITIONAL INFORMATION
GPU memory monitoring:
- `watch -t -n 1 "vulkaninfo 2> /dev/null | grep -A 2 'memoryHeaps\['"`
- `watch -n 1 nvidia-smi`
- `sudo radeontop`

AMD Radeon 6900XT, before resizing:
        memoryHeaps[0]:
                size   = 17163091968 (0x3ff000000) (15.98 GiB)
                budget = 17118306304 (0x3fc54a000) (15.94 GiB)
--
        memoryHeaps[1]:
                size   = 17163091968 (0x3ff000000) (15.98 GiB)
                budget = 14769287168 (0x370517000) (13.75 GiB)

AMD Radeon 6900XT, after 60 seconds of resizing:
        memoryHeaps[0]:
                size   = 17163091968 (0x3ff000000) (15.98 GiB)
                budget = 8399335424 (0x1f4a3b000) (7.82 GiB)
--
        memoryHeaps[1]:
                size   = 17163091968 (0x3ff000000) (15.98 GiB)
                budget = 1272381440 (0x4bd70000) (1.18 GiB)

It consumed over 16 GiB memory visible by the GPU!