Bagl

A modern WebGL2 wrapper with deferred context binding, inspired by the original regl library.

Features

• Deferred Context Binding: Create resources and commands before a WebGL context is available
• WebGL2 Native: Built specifically for WebGL2 with modern features like VAOs and instanced rendering
• State Management: Efficient state caching and diffing for optimal performance
• TypeScript Support: Full TypeScript support with comprehensive type definitions
• Context Loss Handling: Graceful handling of WebGL context loss and restoration
• Resource Management: Automatic cleanup and resource lifecycle management
• Context Object: Built-in time, ticks, width, height tracking for animations
• Uniform Functions: Support for dynamic uniforms with context and props parameters

Installation

npm install bagl-js

Basic Usage

Immediate Context Binding

import { createBagl } from 'bagl-js';

const canvas = document.querySelector('canvas')!;
const bagl = createBagl(canvas);

const drawTriangle = bagl({
  vert: `
    #version 300 es
    precision mediump float;
    in vec2 position;
    void main() {
      gl_Position = vec4(position, 0.0, 1.0);
    }
  `,
  frag: `
    #version 300 es
    precision mediump float;
    out vec4 color;
    void main() {
      color = vec4(0.3, 0.7, 0.9, 1.0);
    }
  `,
  attributes: {
    position: bagl.buffer({
      data: new Float32Array([-1, -1, 1, -1, 0, 1]),
      size: 2 // 2 components per vertex (x, y)
    })
  },
  count: 3
});

bagl.frame(() => {
  bagl.clear({ color: [0, 0, 0, 1] });
  drawTriangle();
});

Deferred Context Binding

import { createBagl } from 'bagl-js';

// Create bagl without a canvas
const bagl = createBagl();

// Prepare resources and commands before DOM is ready
const vertices = bagl.buffer({
  data: new Float32Array([-1, -1, 1, -1, 0, 1]),
  size: 2
});

const drawTriangle = bagl({
  vert: `#version 300 es
         precision mediump float;
         in vec2 position;
         void main() { gl_Position = vec4(position, 0.0, 1.0); }`,
  frag: `#version 300 es
         precision mediump float;
         out vec4 color;
         void main() { color = vec4(0.3, 0.7, 0.9, 1.0); }`,
  attributes: { position: vertices },
  count: 3
});

// Set up render loop
bagl.frame(() => {
  bagl.clear({ color: [0, 0, 0, 1] });
  drawTriangle();
});

// Later, attach to canvas
const canvas = document.querySelector('canvas')!;
bagl.attach(canvas);

Animated Example with Context

import { createBagl } from 'bagl-js';

const bagl = createBagl();

const vertices = bagl.buffer({
  data: new Float32Array([-0.5, -0.5, 0.5, -0.5, 0.0, 0.5]),
  size: 2
});

const drawAnimatedTriangle = bagl({
  vert: `
    #version 300 es
    precision mediump float;
    in vec2 position;
    uniform float time;
    void main() {
      vec2 pos = position;
      pos.x += sin(time) * 0.1;
      pos.y += cos(time * 0.5) * 0.05;
      gl_Position = vec4(pos, 0.0, 1.0);
    }
  `,
  frag: `
    #version 300 es
    precision mediump float;
    uniform float time;
    out vec4 color;
    void main() {
      color = vec4(
        0.5 + 0.5 * sin(time), 
        0.3 + 0.3 * cos(time * 0.7), 
        0.7 + 0.3 * sin(time * 1.3), 
        1.0
      );
    }
  `,
  attributes: { position: vertices },
  uniforms: {
    time: (context, props) => context.time
  },
  count: 3
});

bagl.frame(() => {
  bagl.clear({ color: [0, 0, 0, 1] });
  drawAnimatedTriangle();
});

API Reference

Core Functions

createBagl(canvas?)

Creates a new bagl instance. If a canvas is provided, immediately attaches to it.

bagl.attach(target)

Attaches to a canvas or WebGL2 context.

bagl.detach()

Detaches from the current context and destroys all GPU resources.

bagl.destroy()

Destroys the bagl instance, cancels all animation loops, and cleans up resources.

bagl.attached

Boolean indicating if currently attached to a context.

Context Object

The bagl instance provides a context object with timing and dimension information:

bagl.context.time      // Current time in seconds
bagl.context.ticks     // Frame count
bagl.context.width     // Canvas width
bagl.context.height    // Canvas height
bagl.context.deltaTime // Time since last frame

Resource Creation

bagl.buffer(data)

Creates a buffer for vertex data.

const buffer = bagl.buffer({
  data: new Float32Array([...]),
  size: 3, // Number of components per vertex (1-4)
  type: 'array', // or 'elements'
  usage: 'static' // 'static', 'dynamic', or 'stream'
});

bagl.elements(data)

Creates an element buffer for indexed drawing.

const elements = bagl.elements({
  data: new Uint16Array([...]),
  usage: 'static'
});

bagl.texture(options)

Creates a 2D texture.

const texture = bagl.texture({
  data: imageData,
  width: 512,
  height: 512,
  format: 'rgba',
  min: 'linear',
  mag: 'linear'
});

bagl.cube(options)

Creates a cubemap texture.

bagl.framebuffer(options)

Creates a framebuffer for render-to-texture.

const fbo = bagl.framebuffer({
  color: 1,
  depth: true,
  width: 512,
  height: 512
});

Drawing Commands

bagl(description)

Creates a draw command.

const draw = bagl({
  vert: 'vertex shader source',
  frag: 'fragment shader source',
  attributes: { position: buffer },
  uniforms: { 
    time: (context, props) => context.time,
    resolution: (context, props) => [context.width, context.height]
  },
  count: 3,
  framebuffer: fbo
});

Attributes also support descriptor objects for interleaved layouts:

const interleaved = bagl.buffer({
  // [pos.x, pos.y, uv.x, uv.y] per vertex
  data: new Float32Array([
    -1, -1, 0, 0,
     1, -1, 1, 0,
     0,  1, 0.5, 1
  ]),
  size: 4
});

const drawInterleaved = bagl({
  vert: `
    #version 300 es
    precision mediump float;
    in vec2 position;
    in vec2 uv;
    out vec2 vUv;
    void main() {
      vUv = uv;
      gl_Position = vec4(position, 0.0, 1.0);
    }
  `,
  frag: `
    #version 300 es
    precision mediump float;
    in vec2 vUv;
    out vec4 color;
    void main() {
      color = vec4(vUv, 0.0, 1.0);
    }
  `,
  attributes: {
    position: { buffer: interleaved, size: 2, stride: 16, offset: 0 },
    uv: { buffer: interleaved, size: 2, stride: 16, offset: 8 }
  },
  count: 3
});

stride and offset are in bytes (matching gl.vertexAttribPointer). This is separate from command-level draw offset, which controls where drawing starts.

Uniform Functions

Uniforms can be static values or functions that receive context and props:

uniforms: {
  // Static value
  color: [1, 0, 0, 1],
  
  // Function with context
  time: (context, props) => context.time,
  
  // Function with context and props
  scale: (context, props) => props.scale || 1.0,
  
  // Dynamic matrix
  model: (context, props) => {
    const model = mat4.create();
    mat4.rotateY(model, model, context.time);
    return model;
  }
}

State Management

bagl.clear(options)

Clears the framebuffer.

bagl.clear({
  color: [0, 0, 0, 1],
  depth: 1,
  stencil: 0
});

bagl.frame(callback)

Sets up a render loop.

const cancel = bagl.frame(({ time, deltaTime, tick }) => {
  // Render frame
});

// Later, cancel the loop
cancel();

Context Information

bagl.limits

Access to WebGL2 limits.

bagl.extensions

Available WebGL2 extensions.

Advanced Features

3D Rendering with Lighting

import { createBagl } from 'bagl-js';
import * as mat4 from 'gl-mat4';

const bagl = createBagl();

// Create cube with normals
const positions = bagl.buffer({
  data: new Float32Array([/* cube vertices */]),
  size: 3
});

const normals = bagl.buffer({
  data: new Float32Array([/* cube normals */]),
  size: 3
});

const drawCube = bagl({
  vert: `
    #version 300 es
    precision mediump float;
    in vec3 position;
    in vec3 normal;
    uniform mat4 model, view, projection;
    out vec3 vNormal, vPosition;
    void main() {
      vPosition = position;
      vNormal = normal;
      gl_Position = projection * view * model * vec4(position, 1.0);
    }
  `,
  frag: `
    #version 300 es
    precision mediump float;
    uniform float time;
    uniform mat4 model;
    in vec3 vNormal, vPosition;
    out vec4 color;
    void main() {
      mat3 normalMatrix = mat3(model);
      vec3 worldNormal = normalize(normalMatrix * vNormal);
      vec3 lightDir = normalize(vec3(sin(time), cos(time), 0.5));
      float diffuse = max(dot(worldNormal, lightDir), 0.0);
      vec3 baseColor = vec3(0.8, 0.6, 0.4);
      color = vec4(baseColor * (0.2 + 0.8 * diffuse), 1.0);
    }
  `,
  attributes: { position: positions, normal: normals },
  uniforms: {
    model: (context, props) => {
      const model = mat4.create();
      mat4.rotateY(model, model, context.time * 0.5);
      return model;
    },
    view: (context, props) => {
      const view = mat4.create();
      mat4.translate(view, view, [0, 0, -3]);
      return view;
    },
    projection: (context, props) => {
      const projection = mat4.create();
      const aspect = context.width / context.height;
      mat4.perspective(projection, Math.PI / 4, aspect, 0.1, 100.0);
      return projection;
    },
    time: (context, props) => context.time
  },
  depth: { enable: true, func: 'less' },
  count: 36
});

bagl.frame(() => {
  bagl.clear({ color: [0, 0, 0, 1], depth: 1 });
  drawCube();
});

Context Loss Handling

canvas.addEventListener('webglcontextlost', (e) => {
  e.preventDefault();
  bagl.detach();
});

canvas.addEventListener('webglcontextrestored', () => {
  bagl.attach(canvas);
});

Resource Lifecycle

Resources are automatically managed, but you can manually destroy them:

const buffer = bagl.buffer({ data: new Float32Array([...]) });
// ... use buffer
buffer.destroy(); // Manually destroy

Performance Considerations

• State Diffing: Bagl automatically caches WebGL state and only updates what has changed
• VAOs: Uses WebGL2 Vertex Array Objects for efficient attribute binding
• Resource Pooling: Resources are reused when possible
• Lazy Compilation: Shaders are compiled only when needed
• Loop Management: Animation loops are automatically cancelled when the bagl instance is destroyed

Browser Support

• WebGL2 capable browsers
• Modern browsers with ES2015+ support
• TypeScript 4.0+

License

MIT