breadpaper/EVENTS.md
Breadway 8d8be6ebb1 Add per-output wallpaper set, persist, and theme
Two monitors can keep different wallpapers. `set --output` targets one
awww output, writes that output's bread-theme files, and updates
~/.config/breadpaper/current.json without clobbering the other. Global
set still runs wal + bread-theme reload and stamps every known output.
`apply` and listen-on-monitor-connect restore the saved map. The library
picker binds to its monitor and applies to that output.
2026-08-16 13:06:17 +08:00

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# breadpaper — bread event integration
breadpaper is a wallpaper setter: it works exactly the same with or
without `breadd` running. When breadd *is* present, a successful
`breadpaper set` (or the bare-path shorthand) publishes `bread.paper.changed`
into the shared bread automation fabric, and `breadpaper listen` honors
`bread.command.paper.set` and `bread.command.paper.library`. See the parent `bread` repo's
`Documentation.md` — specifically its "Namespaces" and "Integrating a
bread\* app" sections — for the general convention this follows.
App id: **`paper`**. Transport: `bread-utils`'s `bread_client` module
(feature `bread-client`) — the CLI links it directly. One-shot
`set`/`get` use `BreadClient::connect("paper")` + `emit` only. The
long-running `listen` subcommand holds a `subscribe` open.
`breadpaper listen` is fail-silent if breadd is down: `subscribe`
reconnects with backoff and simply delivers nothing until the daemon
comes back. It also honors `bread.monitor.connected` by re-applying
`~/.config/breadpaper/current.json`. The one-shot `set`/`get`/`library`
/`apply` path does not require `listen`. Modules that want to change
the wallpaper without a listener can still shell out:
```lua
bread.exec("breadpaper set /path/to/image.png")
```
A workflow that publishes the command instead should wait for the
confirmation, not assume the emit finished the set:
```lua
bread.emit("bread.command.paper.set", { path = "/path/to/image.png" })
bread.wait("bread.paper.set.done", { timeout = 10000 })
```
## Events published (`bread.paper.*`)
| Event | Data | When |
|-------|------|------|
| `bread.paper.changed` | `{ "path": "<wallpaper>", "output"?: "<name>" }` | After a successful `set` / `set --output` (awww + palette + theme write), including when `listen` honors `bread.command.paper.set` or restores `current.json` after `bread.monitor.connected`. `path` is the canonical absolute path that was applied. `output` is the compositor output name when only one monitor was targeted; omit (or `null`) means every output. Not emitted on `get`, and not emitted if the set fails. |
| `bread.paper.set.done` | `{ "path": "<wallpaper>", "output"?: "<name>" }` | `bread.command.paper.set` was received and `set()` / `set_on()` succeeded. `path` is the canonical absolute path that was applied. `output` is present when the command targeted one monitor. Not emitted by the one-shot CLI `set` — that path only publishes `changed`. |
| `bread.paper.set.failed` | `{ "error": "<message>", "path"?: "<requested>", "output"?: "<name>" }` | `bread.command.paper.set` was received but `set()` / `set_on()` failed, or `data.path` was missing/not a string. `path` is the requested (not canonical) path when one was supplied. `output` is echoed when the command included one. |
| `bread.paper.library.done` | `{}` | `bread.command.paper.library` was received and a `breadpaper library` process was started. Not emitted by the one-shot CLI `library` / `browse`. |
| `bread.paper.library.failed` | `{ "error": "<message>" }` | `bread.command.paper.library` was received but the library process could not be spawned. |
## Commands honored (`bread.command.paper.*`)
Honored only while `breadpaper listen` is running. A
`bread-emit bread.command.paper.set` with no listener is a silent no-op
— that is the documented bread convention, not a breadpaper bug.
| Verb | Data | Effect |
|------|------|--------|
| `set` | `{ "path": "...", "output"?: "..." }` | Missing `output` calls `set()` (all live outputs, global `wal -i`, `bread-theme reload`). A string `output` calls `set_on()` (that monitor only; no global wal unless it is the focused Hyprland monitor). Emits `bread.paper.set.done` / `.failed`. A successful set also emits `bread.paper.changed`. |
| `library` | `{}` | Spawns `breadpaper library` (GTK picker). Emits `bread.paper.library.done` once the process is started, or `bread.paper.library.failed` if the spawn fails. Clicking a thumbnail in that window applies to the picker's output and publishes `bread.paper.changed`. |
### Not implemented: slideshow / random / next
`breadpaper library` / `browse` is the in-app picker. Do not invent
`bread.command.paper.next` / `.random` / `.cycle` (or matching events)
ahead of a real slideshow feature. Unrecognized verbs are ignored.
## Fail-safe behavior
- If breadd isn't installed or isn't running, `emit` is a silent no-op
(`BreadClient::emit` never blocks or errors the caller) — breadpaper
still sets the wallpaper, generates the palette, and reloads themes.
- `breadpaper listen` does not exit if breadd is down. The command
subscription reconnects automatically (`BreadClient::subscribe`'s
background thread has its own backoff loop); no restart of `listen`
is needed once breadd returns.