https://bugs.freedesktop.org/show_bug.cgi?id=105910
--- Comment #10 from Michel Dänzer michel@daenzer.net --- Things are increasingly pointing to this being an i3 bug. It creates a cairo surface with cairo_xcb_surface_create and copies from that to its parent window. But according to /usr/include/cairo/cairo.h, cairo doesn't initialize the contents of a surface created with cairo_xcb_surface_create, so i3 needs to initialize them explicitly.