Kaolin

A flexible, immediate-mode UI layout library for Rust, inspired by Clay. Kaolin provides a powerful and intuitive API for creating responsive layouts that work across different rendering backends.

Features

• Immediate-mode UI: Build layouts using a declarative, function-based API
• Flexible layout engine: Supports complex flex-box style layouts with growth, shrinking, and constraint-based sizing
• Multi-backend support: Works with Raylib, embedded graphics, and custom renderers
• Type-safe styling: Comprehensive styling system with compile-time safety
• Text rendering: Built-in text layout with wrapping and multi-line support
• No-std compatible: Can be used in embedded environments

Quick Start

Add Kaolin to your Cargo.toml:

[dependencies]
kaolin = "0.1"

# For Raylib support
kaolin = { version = "0.1", features = ["raylib"] }

# For embedded graphics support  
kaolin = { version = "0.1", features = ["embedded"] }

Basic Usage

Here's a simple "Hello, World!" example using the Raylib renderer:

use kaolin::{
    Kaolin, grow, sizing,
    renderers::KaolinRenderer,
    style::{
        FlexStyle, TextStyle,
        layout::{Alignment, Justification, Layout},
    },
};

fn main() {
    use kaolin::renderers::raylib::RaylibRenderer;
    use raylib::color::Color;

    let mut renderer = RaylibRenderer::new(800, 600);
    
    while !renderer.should_close() {
        renderer.draw(|k| {
            k.with(
                FlexStyle::new()
                    .background_color(Color::WHITE)
                    .layout(Layout::new()
                        .alignment(Alignment::Center)
                        .justification(Justification::Center))
                    .sizing(sizing!(grow!())),
                |k| {
                    k.text("Hello, World!", 
                           TextStyle::new()
                               .font_size(48.0)
                               .color(Color::BLACK))
                }
            )
        });
    }
}

Core Concepts

Layout Structure

Kaolin uses a tree-based layout system where each element can contain child elements. The layout is built using a functional, immediate-mode API:

kaolin.draw(|k| {
    k.with(container_style, |k| {
        k.text("Some text", text_style)
         .with(nested_container_style, |k| {
             k.text("Nested content", text_style)
         })
    })
})

Sizing Modes

Kaolin supports several sizing modes for flexible layouts:

Fixed Sizing

// Fixed dimensions
sizing!(fixed!(200.0), fixed!(100.0))  // 200px width, 100px height
sizing!(fixed!(150.0))                 // 150px for both dimensions

Fit-to-Content Sizing

// Fits to content size
sizing!(fit!())                        // No constraints
sizing!(fit!(max_width))               // Maximum width constraint
sizing!(fit!(min_width, max_width))    // Min and max constraints

Growth-based Sizing

// Grows to fill available space
sizing!(grow!())                       // Default growth factor (1.0)
sizing!(grow!(2.0))                    // Custom growth factor
sizing!(grow!(1.0, min, max))          // Growth with constraints

Layout Direction and Alignment

Control how child elements are arranged:

Layout::new()
    .direction(Direction::LeftToRight)     // or TopToBottom, RightToLeft, BottomToTop
    .alignment(Alignment::Center)          // Cross-axis: Start, End, Center, Stretch
    .justification(Justification::Center)  // Main-axis: Start, End, Center, SpaceBetween, SpaceAround
    .gap(10.0)                            // Spacing between children

Styling

Style containers and text with comprehensive options:

// Container styling
FlexStyle::new()
    .background_color(Color::BLUE)
    .corner_radius(8.0)
    .padding(Padding::all(16.0))
    .border(Border::new().width(2.0).color(Color::BLACK))

// Text styling  
TextStyle::new()
    .font_size(24.0)
    .font_id(1)
    .color(Color::WHITE)

Examples

Responsive Layout

Create layouts that adapt to different screen sizes:

k.with(
    FlexStyle::new()
        .layout(Layout::new().direction(Direction::TopToBottom))
        .sizing(sizing!(grow!())),
    |k| {
        // Header
        k.with(
            FlexStyle::new()
                .background_color(Color::DARKBLUE)
                .sizing(sizing!(grow!(), fixed!(60.0))),
            |k| k.text("Header", TextStyle::new().color(Color::WHITE))
        )
        // Content area
        .with(
            FlexStyle::new()
                .background_color(Color::LIGHTGRAY)
                .sizing(sizing!(grow!())),
            |k| {
                k.text("Main Content", TextStyle::new())
            }
        )
        // Footer
        .with(
            FlexStyle::new()
                .background_color(Color::DARKGRAY)
                .sizing(sizing!(grow!(), fixed!(40.0))),
            |k| k.text("Footer", TextStyle::new().color(Color::WHITE))
        )
    }
)

Multi-Column Layout

k.with(
    FlexStyle::new()
        .layout(Layout::new().gap(20.0))
        .sizing(sizing!(grow!())),
    |k| {
        // Sidebar
        k.with(
            FlexStyle::new()
                .background_color(Color::GRAY)
                .sizing(sizing!(fixed!(200.0), grow!())),
            |k| k.text("Sidebar", TextStyle::new())
        )
        // Main content
        .with(
            FlexStyle::new()
                .background_color(Color::WHITE)
                .sizing(sizing!(grow!())),
            |k| k.text("Main Content", TextStyle::new())
        )
    }
)

Rendering Backends

Raylib

Perfect for desktop applications and games:

use kaolin::renderers::raylib::RaylibRenderer;

let mut renderer = RaylibRenderer::new(800, 600);
while !renderer.should_close() {
    renderer.draw(|k| {
        // Your layout here
    });
}

Embedded Graphics

Ideal for embedded systems and small displays:

use kaolin::renderers::embedded::EmbeddedRenderer;
use embedded_graphics_simulator::{SimulatorDisplay, Window};

let mut display = SimulatorDisplay::new(Size::new(128, 64));
let renderer = EmbeddedRenderer::new(&fonts, display.bounding_box());

renderer.onto(&mut display).draw(|k| {
    // Your layout here
});

Custom Renderers

Implement the KaolinRenderer trait to create your own backend:

impl KaolinRenderer for MyRenderer {
    type Color = MyColor;
    
    fn draw(&mut self, draw_fn: impl Fn(Kaolin<Self::Color>)) {
        // Implementation
    }
}

Advanced Features

Text Wrapping

Kaolin automatically handles text wrapping within constrained widths:

k.with(
    FlexStyle::new().sizing(sizing!(fixed!(200.0), fit!())),
    |k| {
        k.text("This is a long text that will automatically wrap to multiple lines", 
               TextStyle::new())
    }
)

Proportional Layouts

Use growth factors to create proportional layouts:

k.with(FlexStyle::new().sizing(sizing!(grow!(1.0))), |k| k)  // Takes 1/4 of space
 .with(FlexStyle::new().sizing(sizing!(grow!(3.0))), |k| k)  // Takes 3/4 of space

Nested Layouts

Create complex layouts by nesting containers:

k.with(outer_container, |k| {
    k.with(inner_container_1, |k| {
        k.text("Content 1", style)
    })
    .with(inner_container_2, |k| {
        k.with(deeply_nested, |k| {
            k.text("Nested content", style)
        })
    })
})

Performance

Kaolin is designed for immediate-mode rendering with minimal allocations:

• Layout calculations are performed each frame but are highly optimized
• Text measurement is cached when possible
• Memory allocations are minimized through careful API design
• No-std compatibility for resource-constrained environments

Contributing

Contributions are welcome! Please feel free to submit issues, feature requests, or pull requests.

License

See the LICENSE file for details.

Inspiration

Kaolin is heavily inspired by Clay, bringing similar concepts to the Rust ecosystem with type safety and zero-cost abstractions.