xfwm4 compositor and the root pixmap.

[Alistair Buxton]

When using compositing, xfwm4 fills it's background with solid grey,
and then drawing the user's wallpaper is left up to xfdesktop. That's
all fine, except that there's a few seconds after xfwm4 starts and
before xfdesktop starts where you can see the ugly grey. If your X11
login screen already set the user's wallpaper this looks bad, as it
goes grey, and then goes back to the correct image.

Xfwm4 has some code inside MONITOR_ROOT_PIXMAP defines which is not
normally enabled. This does two things: it copies any pixmap it finds
at startup, and then it constantly monitors the root for changes.

I think it would be a good idea to always copy the root pixmap on
startup, to avoid the few seconds of grey, even if MONITOR_ROOT_PIXMAP
is not defined. eg:

https://github.com/ali1234/xfwm4/commit/b7baa7aa60cdb80759e0872d0ab5a7cb59ec5c10

Also, the different atoms used by various software to control the
RetainPermanent root pixmaps has many different possible names. Does
it make sense to add these? As well as XROOTPMAP and XSETROOT it
already checks, there is also _XROOTPMAP_ID and ESETROOT_PMAP_ID which
all have exactly the same meaning as far as I can tell. It seems like
it would be easy to add these, at least for the initial copy.

What do you think about this?

-- 
Alistair Buxton
a.j.buxton at gmail.com