---
url: /glimpse/developers.md
---
# How glimpse fits together

glimpse is a set of small programs, each a systemd user service with one job. They read the same
configuration and talk over the session bus. Exec applets are separate programs that the panel starts for
you.

```mermaid
flowchart LR
    target["glimpse-session.target"]
    panel["glimpse-panel"]
    providers["notifications, idle,<br/>settings-daemon, sunset"]
    weather["weather, screenshot portal"]
    others["wallpaper, lock"]
    systemd["systemd user manager"]
    applets["exec applets"]
    target -->|"wants"| panel
    target -->|"wants"| providers
    target -->|"wants"| others
    panel -->|"D-Bus calls"| providers
    panel -->|"D-Bus activation"| weather
    panel -->|"StartTransientUnit"| systemd
    systemd -->|"runs"| applets
    applets -->|"unix socket"| panel
```

## Who owns what

* Each program owns its own state. Nothing else writes it; others ask over D-Bus.
* The panel starts no applet process itself. Every exec applet is a transient systemd unit, so
  systemd owns its process, restarts, memory limit and logs.
* `config.toml` and `panel.toml` are the only configuration. Every program reloads its part when a
  file changes, and only the panel reads `panel.toml`.

[How an applet runs](/developers/exec-applets) follows one applet from config to screen.
[systemd and D-Bus](/developers/systemd) lists the units, bus names and the applet host interface.