[colord] colord integration code examples to query display profile

[Pascal de Bruijn]

Hi,

Currently most programs use the _ICC_PROFILE X11 atom to get the
display ICC to apply before displaying anything on-screen. That
approach has limitations, dual-screen being one of them.

So I'm guessing the following is preferred whenever "Try to use system
profile" is enabled (in any application):

1. Ask colord which profile to apply
2. use _ICC_PROFILE
3. fall back to srgb if all else fails.

Is there any example code, to get a display ICC profile for whatever
display an application is currently placed on?

This is probably the single most common use-case of querying colord,
it would probably help adoption if there were near-drop-in example
code.

Regards,
Pascal de Bruijn