Created attachment 115820 [details]
Screen grab of the described rectangular blur artifact during desktop cube animation

SUMMARY

First bug report.

I use the desktop cube animate desktop effect to switch between virtual desktops.

Since the updated blur modifications introduced in Plasma 5.13 (I think) using desktop cube in combination with the blur desktop effect has led to the upper right quadrant of the screen blurring during transition from one virtual destop to another.

Disable the blur desktop effect and the upper right quadrant does not blur during virtual desktop transition via the desktop cube animation.


STEPS TO REPRODUCE
1. Enable desktop cube desktop effect in System Settings > Desktop Effects
2. Select the desktop cube animation in System Settings > Virtual Desktops
3. Enable the blur desktop effect in System Settings > Desktop Effects
4. Trigger desktop cube animation by moving from one virtual desktop to another

OBSERVED RESULT

There is a rectangular region in the upper right quadrant of the screen that blurs.

Screen grab of this rectangular region blur is attached.

EXPECTED RESULT

This rectangular region of the screen should not blur during virtual desktop transition.

Looks like it may be a hidden region used in desktop cube animation being mistakenly blurred.

Disabling the blur desktop effect is a workaround, but then I am unable to use blur in other parts of my system.

SOFTWARE VERSIONS

Distro: Manjaro
KDE Plasma Version: 5.14.1
KDE Frameworks Version: 5.51
Qt Version: 5.11.2

ADDITIONAL INFORMATION

Using an intel onboard gpu using standard i915 driver with xorg-server 1.20.2.

This issue was introduced in 5.13 and is still present in 5.14.1.

Looked for a similar bug before creating this, did not find one.