Graphics

The machine boots to a graphical interface: a framebuffer, a text renderer, a graphical terminal, and a window manager with a compositor.

The four layers

virtio-gpu framebuffer (virtio_gpu.zig) — the spec 2D path: GET_DISPLAY_INFO → CREATE_2D (B8G8R8X8) → ATTACH_BACKING → SET_SCANOUT → TRANSFER → FLUSH, into a 4K-aligned BSS framebuffer at 1280×720.
Text (text.zig) — a built-in 8×8 bitmap font, putc/puts, cursor, line wrap, and a bounded 128-line scrollback ring.
Road Pops (road_pops.zig) — a tee console: every byte still reaches serial first (the shared evidence seam), and the same banner, prompt, and replies are painted on screen, one present per output batch.
Driving Award (driving_award.zig) — a bounded window registry, z-order, focus, topmost hit-testing, and a dirty-rect compositor that repaints from the lowest dirty window up.

Driving Award

The window manager makes Road Pops window 0 (the full-screen terminal) and a 1 Hz clock overlay window 1 (amber title bar, navy body). win reports the registry; win focus/win raise/win hit manipulate it, and the keyboard read path is gated on terminal focus.

The compositor paints one transfer + flush per dirty batch. Windows are fixed-BSS back-buffers; the fixed terminal and clock are kernel-owned.

Windows from EL0

The syscall seam exposes windows to user programs through slots 12–20: open, fill, present, close, move, raise, get, query, and set_visible — all owner-restricted, with per-process ownership and auto-close on exit.

A desktop on top

Milestone eleven built the zero-heap ui.zig micro-widget toolkit (buttons, text inputs, list views — pure static BSS, no allocation) on top of the window seam, and four applications on top of that: CALC.BIN (calculator), NOTEPAD.BIN (editor), TOP.BIN (process monitor with click-to-kill), and the DESKTOP.BIN launcher — later joined by the FILE.BIN file browser (milestone thirteen). Windows and clicks reach these apps as events through milestone nine's per-process event queues (sys_poll_event/sys_wait_event).