Merge pull request 'ADR 0212: a seat says what it receives, and the machine's hotkeys are a seat' (#366) from decision/0212-contributions-to-a-seat-and-hotkeys into main

2026-10-04 14:42:31 +00:00
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+---
+topic: the mesh
+status: accepted
+date: 2026-10-04
+deciders: jochen
+reconstructed: false
+extends: 02-DECISIONS/0210-a-tools-configuration-is-its-seat-holders-and-every-other-module-extends-it-through-the-seat.md
+---
+
+# 212. A seat says what it receives, and the machine's hotkeys are a seat
+
+## Context
+
+[ADR 0210](0210-a-tools-configuration-is-its-seat-holders-and-every-other-module-extends-it-through-the-seat.md)
+decided that a tool's configuration belongs to its seat's holder, and that every other module extends
+it with a contribution to the seat (§2), in a grain the seat defines (§5). The controller knows only
+three such grains:
+- the environment ([ADR 0203](0203-the-accounts-environment-is-one-modules-and-every-module-contributes-to-it.md));
+- shell code in named slots ([ADR 0204](0204-a-module-contributes-shell-code-to-the-login-shell-in-named-slots.md));
+- the power moments ([ADR 0211](0211-a-machines-power-is-a-node-seat-its-moments-take-contributions-and-its-states-are-events.md)).
+
+Each was a field of its own, with a renderer of its own. Two more appeared on the first workstation:
+
+- **The window manager.** Four modules, the launcher, the clipboard, the wallpaper and the bar, wrote
+  files of their own into its include directory, and so did the laptop's model module. That is what
+  ADR 0210 forbids.
+- **The keys the window manager never sees.** A laptop's vendor keys reach only a hotkey daemon, which
+  reads trigger lines (a key, a state, a command). The daemon's configuration was the laptop module's,
+  although the daemon is a general piece that more than one module has keys for.
+
+A field and a renderer per grain would make every new seat a change to the controller's schema.
+
+## Considered Options
+
+1. **A field per grain,** as before. Rejected: the manifest and the controller grow with every seat
+   that takes contributions.
+2. **Contributions as files in the holder's drop-in directory,** each contributor writing its own.
+   Rejected by ADR 0210: a path in another module's territory.
+3. **One general contribution: a seat, a kind the seat receives, and text in the tool's own grammar.**
+   The seat lists the kinds it receives. The holder places each kind with one placeholder, and the
+   controller concatenates the contributions in module order, each under a comment naming its module.
+   Chosen.
+
+## Decision
+
+**1. A module contributes with `contributions`.** Each entry names:
+- a **seat**;
+- a **kind**, which that seat receives;
+- **content**, text in the tool's own grammar, which the controller does not read.
+
+**2. A seat lists the kinds it receives,** with the comment prefix of its tool's grammar. A
+contribution of a kind its seat does not list is refused at registration.
+
+**3. The holder places a kind with `${contribution:<seat>:<kind>}`** in its own files. The placeholder
+is filled with every module's contribution of that kind on the node:
+- in module order;
+- each preceded by a comment line naming the module;
+- empty when there is none.
+
+A placeholder in a module that does not claim the seat is refused, as ADR 0204 refuses shell slots.
+
+**4. A contribution depends on its seat** (ADR 0210 §3), derived and refused as
+[ADR 0207](0207-a-module-depends-on-the-node-seats-that-apply-its-resources.md) says.
+
+**5. Two seats receive first:**
+
+| seat | kind | what it is |
+|---|---|---|
+| `node-display-session` | `config` | window-manager configuration lines: bindings, start-up commands, rules |
+| `node-hotkeys` (new, node scope) | `trigger` | hotkey-daemon trigger lines: a key, a state, a command |
+
+`node-hotkeys` is in the mesh's own set. Its holder runs the daemon that sees the keys the window
+manager does not, and owns that daemon's configuration and service.
+
+## Consequences
+
+- The window-manager fragments become `config` contributions of their modules: the launcher, the
+  clipboard, the wallpaper, the bar and the laptop model. The window manager's module places them
+  instead of including other modules' files.
+- A hotkey module holds `node-hotkeys`. The laptop's model module contributes its vendor keys
+  instead of writing the daemon's trigger file, and keeps only what is its own: the scripts the keys
+  run.
+- The three earlier grains stay as they are. Folding them into this form is a later change, not
+  required by this record.
+- **What got harder:** a contribution is text the controller does not read, so a malformed line
+  reaches the tool. The holder checks the composed file with the tool's own check where the tool has
+  one (the window manager's), before it reloads.
+
+## How it is checked
+
+| Rule | Checked by |
+|---|---|
+| A contribution names a seat and a kind that seat receives | the catalogue check, which registration runs |
+| The placeholder fills with every module's contribution, in module order, each named | the controller's contribution tests |
+| A placeholder outside the seat's holder is refused | the catalogue check |
+| A contribution derives a dependency on its seat | the controller's resolve tests |
+| `node-hotkeys` is a node seat of the mesh's own set | the seat table's tests |
+
+## References
+
+- [ADR 0203](0203-the-accounts-environment-is-one-modules-and-every-module-contributes-to-it.md),
+  [ADR 0204](0204-a-module-contributes-shell-code-to-the-login-shell-in-named-slots.md),
+  [ADR 0208](0208-the-graphical-session-is-one-module-per-piece-on-the-meshs-seats.md),
+  [ADR 0210](0210-a-tools-configuration-is-its-seat-holders-and-every-other-module-extends-it-through-the-seat.md),
+  [ADR 0211](0211-a-machines-power-is-a-node-seat-its-moments-take-contributions-and-its-states-are-events.md)
+- [To-be 42](../03-DESIGN/01-to-be/42-the-machines-modules-in-order.md)
@@ -193,6 +193,7 @@ python3 00-META/checks/index.py            fail if stale
 - **0202** — [A provider declares what it derives for each consumer, and the mesh tells both ends](0202-a-provider-declares-what-it-derives-for-each-consumer.md)
 - **0207** — [A module depends on the node seats that apply its resources](0207-a-module-depends-on-the-node-seats-that-apply-its-resources.md)
 - **0210** — [A tool's configuration is its seat holder's, and every other module extends it through the seat](0210-a-tools-configuration-is-its-seat-holders-and-every-other-module-extends-it-through-the-seat.md)
+- **0212** — [A seat says what it receives, and the machine's hotkeys are a seat](0212-a-seat-says-what-it-receives-and-the-machines-hotkeys-are-a-seat.md)

 ### Its tiers, from the bottom up

@@ -15,6 +15,7 @@ decisions:
  - 02-DECISIONS/0205-software-the-distribution-does-not-package-ships-as-a-pinned-archive-of-the-module.md
  - 02-DECISIONS/0207-a-module-depends-on-the-node-seats-that-apply-its-resources.md
  - 02-DECISIONS/0208-the-graphical-session-is-one-module-per-piece-on-the-meshs-seats.md
+  - 02-DECISIONS/0212-a-seat-says-what-it-receives-and-the-machines-hotkeys-are-a-seat.md
  - 02-DECISIONS/0211-a-machines-power-is-a-node-seat-its-moments-take-contributions-and-its-states-are-events.md
  - 02-DECISIONS/0210-a-tools-configuration-is-its-seat-holders-and-every-other-module-extends-it-through-the-seat.md
 ---
@@ -111,6 +112,11 @@ not write into its include directory. Each contribution is a dependency on the s
 so assigning one of them without a window manager is refused. The first versions, which still write
 the include files themselves, move to contributions once the controller derives the dependency.

+**Added 2026-10-04.** `triggerhappy` holds `node-hotkeys` on both workstations ([ADR 0212](../../02-DECISIONS/0212-a-seat-says-what-it-receives-and-the-machines-hotkeys-are-a-seat.md)). The
+laptop model's vendor keys become its contribution. The window-manager fragments of the launcher, the
+clipboard, the wallpaper, the bar and the laptop model become `config` contributions to
+`node-display-session`.
+
 ## Phase 3 — one machine model

 The laptop's hardware module (vendor daemon, GPU mode, charge limit, logind, brightness and vendor keys)