The screenshot with region selection behaves weird under i3wm about slop

[naelstrof]

Try using the --opengl mode, slop doesn't actually clear the color of the inner window. Which is dumb, sorry. Default slop is at the mercy of X whether it has junk pixels in it, but clearing the entire window using pure x11 is incredibly slow so I simply don't do it.

--opengl mode is hardware accelerated where I do clear the screen every frame, you'll need slop compiled with it enabled.

You can also use neato shaders with it.

slop --opengl --shader hippie

@naelstrof It works! Thank you!