CosG

A wgpu-based UI library for Rust with a dark violet aesthetic. Built for use in CosinusOS and beyond.

Features

• wgpu renderer — GPU-accelerated rect rendering with SDF rounded corners
• Widget system — Button, Label, Container, Grid out of the box
• ESC system — optional extra style controls per widget (border_radius, shadow, opacity, border)
• Theme system — violet dark theme by default, fully customizable

Quick Start

Add to your Cargo.toml:

[dependencies]
cosg = "0.1.0"

Basic example:

use cosg::*;

fn main() {
    App::new(
        AppConfig {
            title:  "My App".into(),
            width:  800,
            height: 600,
            theme:  Theme::violet_dark(),
        },
        || {
            let btn = Button::new()
                .label("Click me")
                .esc(Esc::new().border_radius(12.0))
                .on_press(|| println!("pressed!"));

            Box::new(
                Container::new()
                    .padding(24.0)
                    .add(Label::new("Hello CosG"))
                    .add(btn),
            )
        },
    )
    .run();
}

Architecture

Widget Trait

Every UI element implements Widget:

pub trait Widget {
    fn layout(&mut self, bounds: Rect, theme: &Theme);
    fn draw(&self, theme: &Theme) -> Vec<DrawRect>;
    fn handle_event(&mut self, event: &WidgetEvent);
    fn rect(&self) -> Rect;
}

Layout is driven top-down — the parent calls layout() on each child with the bounds it allocates.

ESC System

ESC (Extra Style Controls) is a separate layer of optional visual properties that sits on top of the theme. The theme controls colors and font sizes globally; ESC lets you override specific visual properties per widget:

let btn = Button::new()
    .esc(Esc::new()
        .border_radius(8.0)
        .shadow(4.0)
        .opacity(0.9)
        .border_width(1.0)
    );

Theme

let theme = Theme::violet_dark(); // default

You can construct a custom Theme by filling in the struct fields directly — colors are [f32; 4] RGBA.

Layout Primitives

Container — vertical stack with padding:

Container::new()
    .padding(16.0)
    .add(widget_a)
    .add(widget_b)

Grid — place widgets at (col, row):

Grid::new(2, 2)
    .gap(8.0)
    .place(label,  0, 0)
    .place(button, 1, 0)

Roadmap

• Text rendering via glyphon
• TextInput widget
• Horizontal layout in Container
• Focus management (keyboard, Tab)
• Hover/press animations
• colspan / rowspan in Grid
• Scrollable containers
• Shadow rendering in shader

License

MIT