Visual artifacts when using blur with use-damage

[yshui]

GPU, drivers, and screen setup

NVIDIA GTX 1060, driver version: 410.73

Compton version

git-v0.1_beta2-87-g316eac0-2017-04-30

Compton configuration:

backend = "xrender";
blur-background = true;
clear-shadow = true;

Steps of reproduction

Start compton, place a transparent window on top of another window that updates frequently

Expected behavior

No artifacts

Current Behavior

Artifacts, see attached clip

Other details

This bug is caused by incorrect handling of pixels at the edge of damage area in compton's blur code.

blur_artifacts.zip

[yshui]

This is not very hard to fix, except when multi-pass blur is used. Therefore I think it is probably better to remove the multi-pass blur feature.

Object here if you want to keep the feature.

[yshui]

There is a undocumented option resize-damage that makes the damage area bigger to hack around this problem.

This is not an ideal solution, please don't use that.

[yshui]

should have long been fixed. although corner cases creeps back up from time to time. no reason to keep this one open.