agg-gui

agg-gui is an immediate-mode Rust GUI library built on Anti-Grain Geometry (AGG). It provides widgets, flex layout, text editing, markdown, SVG/image rendering, theming, hit-tested input, and optional native/WASM adapter helpers while keeping the rendering model simple: full redraw every frame, deterministic layout, and Y-up coordinates throughout.

Part of the rust-apps suite — a collection of Rust graphics and geometry libraries by Lars Brubaker.

Live Demo

Open interactive WASM demo →

Install

cargo add agg-gui

Optional features:

Feature	Enables
`winit-adapter`	`agg_gui::winit_adapter` — maps winit `MouseButton` / `Modifiers` / `Key` / `CursorIcon` to the crate's input types
`clipboard`	`arboard`-backed system clipboard integration

[dependencies]
agg-gui = { version = "0.1", features = ["winit-adapter", "clipboard"] }

Widgets And Layout

Widget	Description
`Label`	Static text, theme-aware color, left/center/right alignment
`Button`	Themeable background, focus ring, disabled state, click callback
`CollapsingHeader`	Expand/collapse section with animated disclosure
`Checkbox`	Animated check mark, shared state cell for two-way binding
`ComboBox`	Popup-backed single-selection control
`ColorPicker`	Interactive color selection widget
`Slider`	Linear value control with focus ring and keyboard nudge
`DragValue`	Click-drag to increment/decrement numeric values
`RadioGroup`	Single-selection group with shared state
`ProgressBar`	Filled track with optional label
`ToggleSwitch`	Animated on/off toggle
`TextField`	Full text editing: cursor, selection, clipboard, undo/redo
`TextArea`	Multi-line text editing
`Hyperlink`	Underlined link text with click callback
`ImageView`	Image display widget
`ScrollView`	Vertical scroll with drag-thumb and mouse-wheel support
`Window`	Floating panel: draggable title bar, close button, resize handles, collapse
`FlexColumn`	Vertical flex layout with gap, padding, fixed + growing children
`FlexRow`	Horizontal flex layout
`Stack`	Z-ordered overlay layout (for floating windows)
`SizedBox`	Fixed-size constraint wrapper
`Splitter`	Draggable divider between two panes
`TabView`	Tabbed panel switcher with persistable active-tab cell
`TreeView`	Hierarchical list with expand/collapse and drag-and-drop
`Container`	Border + background decorator
`MarkdownView`	Markdown renderer: headings, paragraphs, lists, code blocks, images
`MenuBar` / `PopupMenu` / `Tooltip`	Menu and transient overlay primitives
`Separator`	Horizontal or vertical rule
`Spacer` / `Padding`	Layout utility widgets

Features

Theme system — dark / light / system themes, runtime-switchable; every widget reads colors from ctx.visuals() (no hardcoded colors).
Flex layout — fixed + growing children, per-child margins, cross-axis anchoring, min/max constraints, inner padding.
Event system — Y-up mouse events routed by hit-test with proper Z-order. Capture semantics for drag. Keyboard focus with Tab navigation and focus rings.
Multi-touch — gesture aggregator (current_multi_touch()) exposes per-frame zoom / rotation / translation / pressure deltas. Works on mobile browsers and touchscreen laptops.
Drawing API — DrawCtx covers paths, fills, strokes, rounded rects, circles, arcs, Bézier curves, text, transforms, clipping, compositing layers, image blitting, SVG rendering, and inline GL content. Two implementations: software AGG rasterizer
- halo-AA GL path.
Platform adapters — crate-owned event, cursor, clipboard, font, device-scale, screenshot, and platform types, with optional winit and WASM helper modules.
Inspector — built-in widget-tree inspector overlay highlighting hovered widgets, showing bounds and properties, reporting hover position.

Quick Start

use agg_gui::{App, FlexColumn, Label, Button};
use std::sync::Arc;

let font = Arc::new(agg_gui::Font::from_slice(FONT_BYTES).unwrap());

let root = FlexColumn::new()
    .with_gap(8.0)
    .with_padding(16.0)
    .add(Box::new(Label::new("Hello, world!", Arc::clone(&font))))
    .add(Box::new(
        Button::new("Click me", Arc::clone(&font))
            .on_click(|| println!("clicked"))
    ));

let mut app = App::new(Box::new(root));
// Feed OS events via `app.on_mouse_*` / `app.on_key_down`;
// call `app.layout(size)` + `app.paint(&mut ctx)` each frame.

See the demo shell for a complete example covering 28+ demo windows, themes, persistence, and a GL 3-D cube.

Design Principles

Y-up coordinates everywhere — origin at bottom-left, positive Y upward. One conversion at event ingestion; no per-widget flipping.
Direct-to-surface rendering — AGG paths rasterize straight to the target surface. No retained scene graph, no layout cache to invalidate.
Full redraw every frame — no dirty regions, no incremental update complexity.
Theme via thread-local — set_visuals() writes to a thread-local read by every DrawCtx::visuals() call. Zero plumbing required in widget constructors.
Two-way state binding — Rc<Cell<T>> shared between widgets keeps UI in sync without callbacks.
No unsafe, no RefCell pervasion — the widget tree is owned by App; mutable traversal uses index-based child access to satisfy the borrow checker cleanly.

License

MIT

agg-gui 0.2.0