I am not entirely intimate with plan9, so take this with a grain of salt.
IIRC, everything was a file, down to the graphical UI. This allowed you to interact with the GUI trough the file system, script things, etc. Network connections and computers are also available trough files.
But even more impressive is that this filesystem builds on a relatively simple protocol[1]. Programs and computers can implement this to expose a filesystem view of their internals. The protocol is still used quite a bit, to share files across VMs for instance [2], and more generally when serializing filesystem data over a network link is needed.
I think this allows you to do fancy stuff such as remotely controlling a window on another device, or displaying it on an arbitrary number of machines.
I wish Linux used the filesystem that extensively, to replace things such as d-bus, pulseaudio, gobject, gstreamer, wayland, etc. GNU Hurd has a similar, very interesting mechanism, translators [3] (basically first-class FUSE objects).
Essentially yes. Here's how you get a graphical session on a remote machine: export your local /dev/draw, /dev/mouse, etc. via 9P to the remote machine, then run the GUI on that remote machine. It'll write to /dev/draw, read from /dev/mouse, and so on with no idea that all those file operations are actually traversing the network.
Thinking about it a bit more, indeed. Unless you compress the data of course, which could theoretically be done transparently by the graphical session that owns the framebuffer device.
But I think that /dev/draw (as the name implies) was likely a drawing API? A bit like X11, when the only thing GUI apps did was to draw primitives like circles, lines, text...
IIRC, everything was a file, down to the graphical UI. This allowed you to interact with the GUI trough the file system, script things, etc. Network connections and computers are also available trough files.
But even more impressive is that this filesystem builds on a relatively simple protocol[1]. Programs and computers can implement this to expose a filesystem view of their internals. The protocol is still used quite a bit, to share files across VMs for instance [2], and more generally when serializing filesystem data over a network link is needed.
I think this allows you to do fancy stuff such as remotely controlling a window on another device, or displaying it on an arbitrary number of machines.
I wish Linux used the filesystem that extensively, to replace things such as d-bus, pulseaudio, gobject, gstreamer, wayland, etc. GNU Hurd has a similar, very interesting mechanism, translators [3] (basically first-class FUSE objects).
[1] https://en.wikipedia.org/wiki/9P_(protocol)
[2] https://wiki.qemu.org/Documentation/9psetup
[3] https://www.gnu.org/software/hurd/hurd/translator.html