alpymist

ADR 0030

A game for a screen with no desktop, and for systems that are not ours

accepted View source

Context

Solitaire (ADR 0029's addenda) is a window on the desktop. Its rules, its table and the hand that plays it are a library with no window in it, and Denise draws to a display through DRM/KMS and reads a mouse and a keyboard from the kernel without a compositor: the login screen, the installer and the splash are made that way.

So the same game can be shown on a text console, on a machine with no desktop installed, on a Raspberry Pi. That is a program somebody may want who does not run Alpymist, which nothing of ours has been until now: everything else is a package for our own repository.

Decision

alpymist-solitaire-console is the game on a screen with no desktop. A crate of its own in the console build group, over alpymist-solitaire built without its window: the display opened as the login screen opens it, the mouse, a touch screen and the keyboard from denise-evdev, and the pointer painted by the program. Everything a hand does and everything a game shows is the library's play, the same as in the window. For that, alpymist-widget's Wayland host is a feature, on by default; without it that crate is the fonts, the colours and the controls.

It is given away as one file, and not as a package. Each release attaches alpymist-solitaire-console-ARCH, with its SHA-256, for x86_64, aarch64 and armv7: linked statically against musl, so it asks the system it runs on for nothing. ci/build-standalone.sh builds all three on one machine with the linker and the C runtime that come with each Rust target, and no cross compiler. The packages stay dynamic, as Alpine's are (ADR 0004); this is built apart from them, in a directory of its own.

It does not fail a release. The job that builds it may fail without failing the run stable is published from. Fewer files on the release than there should be is how that shows.

Alpymist does not install it. It needs the display and the input devices, which is root, or an account in video and input. An account in input can read every keystroke typed on the machine, and ADR 0011 keeps accounts out of it; a package that only worked for someone who had undone that would be an invitation to. Where there is a desktop there is the window. Someone on Alpymist's own text console can download the file like anyone else, and run it as root.

It leaves by Ctrl+Q, Ctrl+C or a Quit button on the bar, since there is no window to close, and asks first when a game is under way.

The table is painted once and kept. A frame is that memory copied where the pointer and the cards in the hand were and are; a button lit, a clock's second and a letter typed into a panel are painted again only inside what they cover. On a Raspberry Pi 3A+ a table painted whole is 48 ms, a card carried 3 ms and a button lit under one. It is what Denise's own examples do with a tree's damage, done by hand for a game with no tree.

It carries no font. Where the theme's is not installed it writes with the first plain sans-serif the system has, DejaVu, Liberation or Noto, and with Denise's built-in bitmap where there is none.

Consequences

  • The first thing of ours that is for other systems. It is a game, takes nothing from the machine but a screen and a hand, and keeps one file, ~/.local/state/alpymist/solitaire: the back, the way of turning and the best games. Nothing is sent anywhere.
  • While it runs, another console cannot be switched to: it holds the display and has muted the console's keyboard. The login screen lets go for another console and this does not yet.
  • It looks at the mouse every 3 ms and does not sleep until the mouse moves, as Denise's examples do: that takes a wait on the devices' own descriptors, which the input crate does not hand out without unsafe.
  • --nearly-out, a game five cards from its end, and --bench, what a frame costs on the machine, are there and not in the usage.
  • 2.4 MiB a file, with the cards and the backs in it.
  • Tried: played on a virtual machine's text console and on a Raspberry Pi 3A+ running Alpine, both aarch64, with a mouse and a keyboard; the aarch64 file started on Debian 12 in a container. Not tried: the armv7 and x86_64 files run at all, a touch screen, a second display, Raspberry Pi OS, and a system with none of the fonts looked for.