d0f7acf9eb
An x86-64 operating system built from xv6, now largely rewritten: SMP, a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF rasteriser, and a Linux-numbered syscall ABI. No history before this point -- the tree was never under version control. This commit exists so the rename that follows has something to undo to.
1.8 KiB
Schcom — the Schunix Compositor
Owns the display. Every pixel that reaches the screen goes through it.
Clients do not draw to the framebuffer; they draw into their own buffers and hand them over. Schcom decides what is on top of what, composites the result, and presents it. It also owns input: it reads the raw event devices and sends each event to whichever client should have it.
That is the whole job. Window placement is not part of it — that is SchWM's, and Schcom exposes a protocol for it rather than implementing policy itself.
Status
Not started. Scoped only.
What it needs from the kernel first
| Need | State |
|---|---|
Shared memory (shmget/shmat/shmdt) |
done |
mmap of /dev/fb0 |
done |
| Framebuffer geometry via the fbdev ioctls | done |
Unix domain sockets, with SCM_RIGHTS |
missing — socket() is a NO_LINUX stub |
| Raw input events — key down/up with modifiers | missing — input only arrives cooked, through the tty line discipline |
| Mode setting and double buffering | missing — needs the virtio-gpu driver |
The two marked missing are hard blockers, not inconveniences. A client and the compositor have to pass a buffer handle between them, and a pipe cannot carry one. And a compositor that reads the tty gets line-buffered text delivered to a single foreground process, which is not input in any sense it can use.
Design notes, so far
- Buffers are shared memory, not pipes. A pipe means copying every frame; at 800×600×32 that is 1.9 MB per frame per client. shm exists for this.
- One protocol, versioned from the start. SchWM and SchDE are separate programs, so the protocol is a real compatibility surface from day one, not after the fact.
- Policy belongs to SchWM. If Schcom starts deciding where windows go, the split has already failed.