04 · Interface

Everything the player sees that is not the 3D world: menus, dialogs, the HUD, chat, and messages.

All of it is client side. See Client/server split if you are not sure which side your code is running on.

Page	Read it for
GUI system	`.gui` files, control profiles, Canvas, dialogs, the GUI editor
HUD	In-game HUD controls, reticles, weapon and inventory HUD registration
Text and messaging	Chat, `bottomPrint`, colour codes, tagged strings, message callbacks

The shape of it

flowchart TD
    CANVAS["Canvas<br/>the root — one content, a stack of dialogs"]
    CONTENT["Content control<br/>e.g. PlayGui in game, LobbyGui in the shell"]
    DLG["Dialog stack<br/>pushDialog / popDialog"]
    PROF["GuiControlProfile<br/>shared font, colour, bitmap, sound"]
    CTRL["Controls<br/>GuiTextCtrl, GuiButtonCtrl, ShellPaneCtrl, …"]

    CANVAS --> CONTENT
    CANVAS --> DLG
    CONTENT --> CTRL
    DLG --> CTRL
    PROF -.styles.-> CTRL

Canvas has exactly one content control at a time and a stack of dialogs on top of it. The shipped scripts call pushDialog / popDialog 183 times between them and setContent 29 times [script] — dialogs are the normal way to show something, and content switches are reserved for major mode changes (shell → loading → game).

Where the files are

base/scripts.vl2
├── gui/           136 .gui files — the layouts
└── scripts/       the .cs partners holding the behaviour
    ├── LobbyGui.cs, GameGui.cs, OptionsDlg.cs, ChatGui.cs, …
    ├── hud.cs, inventoryHud.cs, objectiveHud.cs, chatMenuHud.cs
    └── message.cs, centerPrint.cs

A .gui file is a layout; its behaviour lives in a same-named .cs. Both are loaded from console_end.cs [script].

Under the community patches

This is the section the patches change most. If you are writing a UI mod, read the “Under the community patches” section on each page here before you start.

The headline items:

Change	Page
Every vanilla font is substituted for a `.sdft` — layouts tuned to vanilla metrics will shift	GUI system
Render scale, UI scale, and UI aspect are user-controlled — the 640×480 assumption no longer holds	GUI system
The Video options panel is torn down and rebuilt	GUI system
The HUD repositions by aspect ratio; two opacity defaults change	HUD
Inbound chat is tag-filtered and optionally word-filtered	Text and messaging

What does not change: .gui syntax, control classes, GuiControlProfile fields, the Canvas dialog stack, onWake / onSleep, GuiMLTextCtrl markup, the $WeaponsHudData registration mechanism, and the whole messageClient / clientCmd API.