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let canvas, gl;
const createShader = (gl, type, source) => {
const shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
const success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
if (success) return shader;
console.error(gl.getShaderInfoLog(shader));
gl.deleteShader(shader);
};
const createProgram = (gl, vertexShader, fragmentShader) => {
const program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
const success = gl.getProgramParameter(program, gl.LINK_STATUS);
if (success) return program;
console.error(gl.getProgramInfoLog(program));
gl.deleteProgram(program);
};
const initGL = () => {
const vertexShaderSource = `
attribute vec2 a_position;
uniform vec2 u_resolution;
void main() {
vec2 inverted = vec2(a_position.x, u_resolution.y - a_position.y - 1.0); // !! :)
vec2 zeroToOne = inverted / u_resolution;
vec2 zeroToTwo = zeroToOne * 2.0;
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace, 0, 1);
}`;
const fragmentShaderSource = `
precision mediump float;
uniform vec4 u_color;
void main() {
gl_FragColor = u_color;
}`;
const vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexShaderSource);
const fragmentShader = createShader(
gl,
gl.FRAGMENT_SHADER,
fragmentShaderSource,
);
const program = createProgram(gl, vertexShader, fragmentShader);
const positionAttributeLocation = gl.getAttribLocation(program, "a_position");
const colorUniformLocation = gl.getUniformLocation(program, "u_color");
const resolutionUniformLocation = gl.getUniformLocation(
program,
"u_resolution",
);
const positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
gl.useProgram(program);
gl.uniform2f(resolutionUniformLocation, gl.canvas.width, gl.canvas.height);
gl.enableVertexAttribArray(positionAttributeLocation);
gl.vertexAttribPointer(positionAttributeLocation, 2, gl.FLOAT, false, 0, 0);
return (positions, color) => {
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
gl.uniform4f(colorUniformLocation, ...color);
gl.drawArrays(gl.TRIANGLE_FAN, 0, 4);
};
};
let draw;
self.onmessage = (msg) => {
if (msg.data == "clear") {
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
} else if ("canvas" in msg.data) {
canvas = msg.data.canvas;
gl = canvas.getContext("webgl", { preserveDrawingBuffer: true });
if (!gl) alert("no webgl");
gl.viewport(0, 0, canvas.width, canvas.height);
draw = initGL();
} else {
[color, x, y, width, height] = msg.data;
draw([x, y + height, x + width, y + height, x + width, y, x, y], color);
}
};
// self.onmessage = (msg) => {
// if (msg.data == "clear") {
// gl.clearRect(0, 0, canvas.width, canvas.height);
// } else if ("canvas" in msg.data) {
// canvas = msg.data.canvas;
// gl = canvas.getContext("2d");
// } else {
// [color, x, y, width, height] = msg.data;
// if (width < 2 || height < 2) return;
// gl.fillStyle = color;
// gl.fillRect(x, y, width, height);
// }
// };
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