UQML for VS Code

Language support for UQML — a declarative, reactive language for Unity. UI Toolkit is its primary target, but the language is general-purpose and also describes non-visual, reactive objects. Compiles .uqml files to C#.

Powered by the uqml-lsp language server, bundled with the extension — no .NET install required.

What .uqml looks like

using UnityEngine.UIElements
using Uqml

public VisualElement {
    id: root
    property int count: 0
    property float glow: 1

    signal capped(value: int)              // an event this element can emit

    method increment() {                   // a method — callable from handlers
        count = count + 1
        if (count > 10) capped(count)
    }

    onCountChanged: fade.Start()           // property-change handler
    onCapped: (value) => { count = 0 }     // event handler

    NumberAnimation on glow {              // animate a property over time
        id: fade
        from: 0
        to: 1
        duration: 300
    }

    Label {
        text: "Count: " + count
        style.color: "#e0e0e0"             // a style property
        style.opacity: root.glow           // bound to the animated property
    }
    Button {
        text: "+1"
        onClicked: root.increment()
    }
}

Declare reactive property state, respond with on…Changed handlers, emit signal events, group logic into methods, set style.* properties, and attach NumberAnimations — all declaratively, with no manual change notifications.

Features

• Diagnostics — parse and type errors as you type, with the same UQ#### codes the Unity importer reports.
• Completion and hover — type-aware against your project's compiled assemblies (resolved reflection-only; your code never runs).
• Semantic highlighting, document symbols, and folding.
• Go to definition and find references across ids and members.
• Rename (with prepare) and document formatting.

Requirements

Open a folder (your Unity project). The server anchors diagnostics to the workspace root. Type-aware features light up once the project has been compiled by Unity at least once (they read Library/ScriptAssemblies).

Settings

• uqml.trace.server — trace LSP traffic (off | messages | verbose) to the uqml language server output channel.

Development

Running against a source checkout instead of the bundled server: set the UQML_LSP_DLL environment variable to a built uqml-lsp.dll, or open the uqml repo itself (the extension finds src/Uqml.LanguageServer/bin/…/uqml-lsp.dll).

Support & Feedback

• Discussions: Ask questions, share ideas, and get help.
• Issue Tracker: Report bugs or request features.