Do not force screen compositing if X server does not support it.
main: only enable screen compositing if requested and available.
Creating a DisplayInfo
object checks if the X server supports
compositing, but the initialization code discarded this information and
forcefully enabled screen compositing if compositing support was
compiled into xfwm4 and it was not explicitly disabled via the command
line switch (default: on
).
On recent X servers, this doesn't seem to cause visual issues at first
glance (tested via Xephyr and the COMPOSITE
extension disabled), but
X2Go/NX breaks in horrible ways - each window has a black frame around
it (where shadows are supposed to be) and screen updates are not working
properly.
In any case, screen compositing should not be enabled if the X server
does not support it to begin with, so respect what
compositorInitDisplay()
detected.