Moving the mouse repainted the whole screen. At 1280x800 that is a
million pixels of desktop fill, every surface re-blitted, and a 4 MB copy
to the framebuffer -- per event. Under emulation the pointer lagged the
mouse by whole seconds, and that was not the emulation's fault: moving a
10x10 cursor does not require touching four megabytes.
Two changes, and the second matters as much as the first.
Damage tracking: one rectangle, unioned from whatever actually changed,
and only those rows are redrawn and copied out. A pointer move damages
where it was and where it is; a commit damages that surface; a client
going away damages what it had. One rectangle rather than a list, because
in practice the changes are a cursor and the window under it, and a list
costs more bookkeeping than it saves.
Draining input: a single mouse movement produces a burst of EV_REL ending
in EV_SYN, and the loop handled one event per poll and repainted. So the
compositor rendered every intermediate position of a cursor that was
never seen at those positions. Both queues are now drained before
anything is painted. handle_input grew a distinct "queue empty" return
for it -- EV_SYN changes nothing but is not the end of the burst, and a
drain that stopped there would leave the rest queued.
Also cuts the loader's resolution prompt from four seconds to one and a
half, on both the BIOS and UEFI paths. Four was mine and it was too long:
it is paid on every unattended boot, and adding four seconds to every
start to offer a menu nobody usually wants makes the common case worse to
serve the rare one.
schcom-test passes, including two overlapping clients and stacking order.
bootcheck 108 [ok].
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Clients connect over a Unix socket, are handed a shared buffer, draw into
it and commit; Schcom composites and presents. Both of the hard blockers
its README listed -- unix domain sockets and raw input events -- have been
done for a while, so nothing was in the way.
The model is Wayland's, on purpose. A surface is not a window: it is a
rectangle of pixels with no policy attached, because placement belongs to
SchWM and the moment this program starts deciding where windows go the
split has failed. Nothing is shown until COMMIT, so a client halfway
through drawing is never presented. The compositor tells clients when to
draw rather than letting them render frames nobody sees.
Wayland is MIT-licensed and supporting it later is intended, so the
divergences are the ones that are cheap to undo: a buffer handle is a
System V shm id rather than an fd over SCM_RIGHTS, and the message
carries a handle_kind field so switching is a new value rather than a
protocol break. Every message carries its own length, so an unknown
message is skipped instead of desynchronising the stream -- which is what
lets a v0 compositor survive a v1 client.
The compositor owns the shm segment, not the client: it has to survive a
client crashing mid-frame, and it must not be something a client can
resize underneath it. A dropped connection takes its surfaces and their
segments with it.
Composites into a back buffer and copies once, because compositing
straight into the framebuffer shows every intermediate state -- the
flicker would be the whole desktop being repainted under the user's eyes.
projects/ gets build glue for the first time: `make projects` builds
against the sysroot's libc and stages into sysroot/bin. It is not a
dependency of anything above it, and `make` never descends there.
Verified by `make schcom-test`, which boots SchOS, runs the compositor and
a client, screendumps the framebuffer and asserts the pixels on the host.
That last part is the point -- the compositor reporting that it
composited something proves nothing, and a screenshot nobody inspects
proves less. It checks the client's colour mid-surface, the compositor's
background, and the white border exactly at the requested origin, so
"arrived" and "arrived at the wrong offset" cannot pass for each other.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
