59aff881ac
1.0: the acceptance test drops its reboot clause (a live system is the finish line) and passes. Schcom is kept with a job: the installer's GUI first, SchDE on top later (roadmap section 5). The old 'LDLS ships no Linux code' policy is gone from ldls/devices/licensing/Makefile/.gitignore/ldlsd; NOTICE records the r8169 modules (GPL-2.0-only) and the Realtek firmware. The download button points at the v0.1.0 release asset; the stale 64 MB ISO under docs/Website is removed. mkaroot.sh's -dumbSched comment no longer claims SchOS has no threads. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EVRhxi9zpdW2uDUN4FVcao
77 lines
4.7 KiB
Markdown
77 lines
4.7 KiB
Markdown
# The desktop: Xorg on the framebuffer
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The desktop is X11, on the framebuffer: Alpine's `xorg-server` with the `fbdev` video
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driver and the `evdev` input driver, Window Maker as the window manager, and `xterm`.
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`startx` runs `wmaker`. Nothing here is written by SchOS except the kernel interfaces it
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stands on and four small files in `tools/posix/mkaroot.sh`.
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**Xorg is the desktop for now, not for ever.** SchOS's own compositor, Schcom, is the road to a desktop of its own — the installer's
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GUI first, SchDE on top later ([../plan/roadmap.md](../plan/roadmap.md) §5).
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## Why X and not Wayland
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Every Wayland compositor worth running — labwc, and everything built on wlroots — needs
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DRM/KMS, libinput, udev and libseat. DRM/KMS is the largest of them by far: a kernel graphics
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subsystem, and in practice a great deal taken from Linux. Xorg runs on a plain framebuffer
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through `fbdev` and reads input through `evdev`, both interfaces SchOS already had. That is
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the shorter road to a desktop by a long way, and it brings the window managers with it.
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DRM/KMS is not planned; libinput, udev and libseat are worth having for their own sake and
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may come later.
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## What it stands on
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| **fbdev** | `/dev/fb0` speaks Linux's fbdev ([graphics.md](graphics.md#devfb0-and-how-xorg-draws)) |
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| **evdev** | `/dev/input/event0` (every keyboard) and `event1` (every mouse and touchpad) with Linux's queries, LED writes and key/button/relative-axis bits |
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| **VTs** | `/dev/tty0`, `VT_SETMODE(VT_PROCESS)`, `KD_GRAPHICS`, the release/acquire handshake ([terminals.md](terminals.md)) |
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| **dlopen** | Xorg loads its drivers as modules, so `exec` does dynamic linking ([kernel.md](kernel.md)) |
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| **sysfs** | `/sys/bus/pci/devices/*/{boot_vga,enable,graphics/fb0}`, which libpciaccess reads |
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| **ptys** | `xterm` runs its shell on a pseudo-terminal |
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| **Unix sockets** | the X11 socket, abstract names, `SO_PEERCRED`, `flock` |
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| **headers** | `<linux/*.h>` in the build sysroot, as `ports/linux-headers` |
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`cmd/xready` checks every one of the kernel calls Xorg makes before it draws anything — the
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evdev queries, the fbdev calls, the console calls, and the `/sys` files — one at a time, on a
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terminal of its own, and puts everything back. The calls were written against what the
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programs are documented to do; each step past it found one that was not, which is what running
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the real program is for.
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## The four files
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- **`/root/.xserverrc`** starts `X` on the VT `startx` was started from (startx works that
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out only when `uname -s` says Linux, and SchOS's says SchIFT) with **`-dumbSched`**. Xorg
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normally reads input on a thread of its own; when SchOS had no threads the server crashed
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the first time a client disconnected, in `pthread_join` on a thread that was never made, and
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`-dumbSched` is Xorg's own switch for input on the main loop. Threads exist now; the switch
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is still on, and nobody has run the server without it since.
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- **`/root/.xinitrc`** is `exec wmaker`. Without it xinit falls back to twm and an xterm, which
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are not in the image.
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- **`/etc/X11/xorg.conf.d/10-schos.conf`** names the input devices. Alpine's Xorg asks udev for
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them, SchOS has no udev, and X came up with no keyboard and no mouse: the pointer did not
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move and nothing could end the session. SchOS has exactly two input nodes whatever the
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machine, so a fixed list is the whole answer (`AutoAddDevices` off, Ctrl+Alt+Backspace
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enabled).
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- **`/etc/asound.conf`** is for sound, not X ([audio.md](audio.md)).
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## Using it
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Twelve virtual terminals, switched with Ctrl+Alt+F1–F12 — on the console and under X
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alike, because X owns the keyboard while it runs and switches only with that chord. `startx` on
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a terminal runs the desktop there; Ctrl+Alt+Backspace ends the session and gives the terminal
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back. Window Maker, `xterm`, `xeyes`, `xclock`, `xcalc`, DejaVu fonts; SDL 2 games
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(`lbreakouthd`) and NetSurf, a GTK 3 browser, run in it.
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Touchpads that sit on an I2C bus (most laptops) are driven by `kernel/acpi/i2c_hid.c`, found
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through ACPI, and reach X as a mouse: pointer, click and tap.
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## What it does not do
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- **No acceleration.** Software rendering to the framebuffer: no DRM, no glamor, no DRI, no
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OpenGL beyond what software gives. GPU drivers are a plan ([../plan/gpu.md](../plan/gpu.md)).
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- **No udev.** Input devices are named in a config file, not found; `/sys` has no `devices`
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tree and no uevent socket.
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- **Touchpads are mice**: no two-finger scroll, no gestures, no palm rejection.
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- **No resolution change from inside X.** The mode is the console's; `schmode` changes the
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`vgpud` head only, and the loader's menu is where a real panel's mode is chosen.
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- **Not a security boundary.** X runs as root on a system that enforces no file permissions.
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