reliable as a source of truth about which monitors and screens are
actually in use. Each one comes with its own collection of `crtc`,
but you can just skip the ones that return `null`, giving you a
reliable list of the "active and visible" screens that the user is
currently looking at. Excellent! This means that I'm one step closer
to having a viable solution!
I also discovered the [xcb_util](https://xcb.freedesktop.org/XcbUtil/)
library of helpful utilities has a function called
`xcb_aux_get_screen` for getting the root screen because everyone was
weirded out by that list traversal algorithm.
The source code to [xedgewarp](https://github.com/Airblader/xedgewarp)
was invaluable in revealing these secrets to me.
So far this little toy compiles down to only 35KB, and that includes
using `std::cout` and `std::vector`! I wonder how big the Rust
version will be. Yeah, yeah, I know, it cheats by having lots of
itself hidden in the kernel.
Next up: Actually knowing what the rotation status is.
monstrous things allocated in memory that you just have to "know" are
of a certain structure. In this case, we used `xcb_screen_next` to
say that we want the first (and all) screens attached to our current
X11 session. And we used
`xcb_setup_roots_iterator(xcb_get_setup(connection))` to initialize
our iterator to our connection object in local memory.
Other things we've learned along the way: the file description that
represents our connection can be a TCP/IP socket or a Unix Domain
socket (a filesystem socket, named or not), and the only way to know
which is to find if there's a hostname before the colon ':' in the
display name of the server. Not sure how that's going to work.
Also, found a really good reference: [Basic Graphics Tutorial with
XCB](https://www.x.org/releases/X11R7.6/doc/libxcb/tutorial/index.html).
It doesn't cover our specific use-case, but it's worth looking into.
Elf M. Sternberg