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Modder API

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DooDesch edited this page Jun 26, 2026 · 1 revision

Modder API

Hotline gives any mod a ready-made panel in the unified overlay, and it is a zero-overhead no-op when Hotline is not installed - so you can ship the integration unconditionally with no hard dependency. Full working example: ScheduleOne-HotlineExample.

Add the shim

  • Copy-in source (recommended): drop Hotline.cs (from the example repo) into your mod project. It compiles into your DLL - nothing extra to ship.
  • Reference the DLL: reference Hotline.Api.dll.

Both bind to the running Hotline host by reflection, so they share no type with it and work regardless of load order (registrations queue until the host is up).

Register a panel

using Hotline.Api;   // Hud, Panel, HotlineKey, LogLevel

Hud.RegisterPanel("MyMod", "My Mod")
   .Text(() => "queue = " + _queue.Count)                  // a free, multi-line readout
   .Action("Reload", Reload)                               // a button (replaces a debug hotkey)
   .Toggle("Verbose", () => _verbose, v => _verbose = v)   // an on/off control
   .Hotkey("Reload", HotlineKey.F8, Reload)                // an optional central hotkey (Hotline polls it)
   .Log();                                                 // show this panel's log channel

That is the whole UI - no OnGUI, no uGUI, no per-mod hotkey. The player opens the overlay with the master key (F6); your panel is a window there, toggled from the Overview (or hotline panel MyMod on).

The builder

  • .Text(Func<string>) - a multi-line readout, polled by Hotline a few times a second.
  • .Action(string label, Action run) - a button; runs on the Unity main thread when clicked.
  • .Toggle(string label, Func<bool> get, Action<bool> set) - an on/off control.
  • .Hotkey(string label, HotlineKey key, Action run) - bind a key centrally; Hotline owns the polling and flags conflicts. Pass HotlineKey.None to skip the key.
  • .Log() - show this panel's log channel; send lines with .Write("...") or Hud.Log("MyMod", "...").

The lower-level static calls (Hud.RegisterPanel/RegisterAction/RegisterToggle/RegisterText/RegisterHotkey/Log) exist too if you prefer them to the builder.

Already using a raw function key?

If your mod polls a raw Input.GetKeyDown(KeyCode.Fx), Hotline auto-detects it and adds a button for it to your panel anyway (see Auto-Intercepted Hotkeys). Registering a panel as above is the clean way and gives you text, toggles and a log on top.

Rules

  • Call from the Unity main thread. Action/toggle/text delegates are invoked by Hotline on the main thread, so they may safely touch game objects.
  • Use your mod name as the panel id so an auto-detected hotkey lands in the same panel.
  • Every call is a no-op when Hotline is absent; there is no hard dependency.

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