blurred/transparent frame includes window client area and flickers (experimental backends)

[mikejzx]

Platform

Gentoo

GPU, drivers, and screen setup

NVIDIA GTX 1050, nvidia-drivers 495.46-r10

name of display: :0
display: :0  screen: 0
direct rendering: Yes
Memory info (GL_NVX_gpu_memory_info):
    Dedicated video memory: 2048 MB
    Total available memory: 2048 MB
    Currently available dedicated video memory: 1711 MB
OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: NVIDIA GeForce GTX 1050/PCIe/SSE2
OpenGL core profile version string: 4.6.0 NVIDIA 495.46
OpenGL core profile shading language version string: 4.60 NVIDIA
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile

OpenGL version string: 4.6.0 NVIDIA 495.46
OpenGL shading language version string: 4.60 NVIDIA
OpenGL context flags: (none)
OpenGL profile mask: (none)

OpenGL ES profile version string: OpenGL ES 3.2 NVIDIA 495.46
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20

Environment

openbox

picom version

vgit-31e58 (experimental backends)

Diagnostics

**Version:** vgit-31e58

### Extensions:

* Shape: Yes
* XRandR: Yes
* Present: Present

### Misc:

* Use Overlay: No
  (Another compositor is already running)
* Config file used: /home/mike/.config/picom.con

### Drivers (inaccurate):

NVIDIA

### Backend: glx

* Driver vendors:
 * GLX: NVIDIA Corporation
 * GL: NVIDIA Corporation
* GL renderer: NVIDIA GeForce GTX 1050/PCIe/SSE2

Configuration:

Configuration file

backend = "glx";
glx-no-stencil = true;
glx-no-rebind-pixmap = true;
glx-copy-from-front = false;
use-damage = true;
refresh-rate = 60;
vsync = true;
xrender-sync-fence = false;

mark-wmwin-focused = true;
mark-ovredir-focused = true;
use-ewmh-active-win = true;
unredir-if-possible = true;

detect-client-opacity = false;
detect-transient = true;
detect-client-leader = true;
inactive-opacity-override = false;
frame-opacity=0.6;
blur-background = true;
blur-background-frame = true;
blur-background-fixed = true;
blur:
{
        method = "dual_kawase";
        strength = 3;
}

... rest is omitted for brevity

Steps of reproduction

Specifc reproduction steps may be difficult as it isn't always consistent. However, it seems that it is somehow affected by which workspaces the windows are on, and that all windows on only some workspaces (at seemingly random times) suffer from the effect

Expected behavior

Blurred+transparent frames should only contain what is actually behind the window (window client area is part of the window, not behind it)

Current Behavior

The window frame seems to sometimes render "above" the client area and hence causes a strange "bleeding" effect. This is accompanied by a "flicker" on window updates

Other details

see example video; I've exaggerated the size and transparency of the frame to make the effect more obvious

https://user-images.githubusercontent.com/42143005/148721156-0fc68357-5b9c-42b3-b673-8f40028f0434.mp4

Thanks! (also for this great piece of software)