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text_dropin.html
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<!-- vim: sw=4 ts=4 expandtab smartindent ft=javascript
-->
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>WebGL Demo</title>
<style> document, body { margin: 0px; padding: 0px; overflow: hidden; } </style>
</head>
<body>
<canvas id="glcanvas"></canvas>
<script>
/*
* [ ] reuse gpu buffers 'cross frames
* [ ] don't invert mat4 in drawText
* [ ] have frame ring buffer for scratch mats
*/
function lerp(v0, v1, t) { return (1 - t) * v0 + t * v1; }
function inv_lerp(min, max, p) { return (p - min) / (max - min); }
function mat4_create() {
let out = new Float32Array(16);
out[0] = 1;
out[5] = 1;
out[10] = 1;
out[15] = 1;
return out;
}
function mat4_ortho(out, left, right, bottom, top, near, far) {
let lr = 1 / (left - right);
let bt = 1 / (bottom - top);
let nf = 1 / (near - far);
out[0] = -2 * lr;
out[1] = 0;
out[2] = 0;
out[3] = 0;
out[4] = 0;
out[5] = -2 * bt;
out[6] = 0;
out[7] = 0;
out[8] = 0;
out[9] = 0;
out[10] = 2 * nf;
out[11] = 0;
out[12] = (left + right) * lr;
out[13] = (top + bottom) * bt;
out[14] = (far + near) * nf;
out[15] = 1;
return out;
}
const ALIGN_LEFT = 0;
const ALIGN_CENTER = 1;
/* higher number = prettier text using more VRAM */
const SDF_FONT_SIZE = 48;
/* one draw call's worth of font data (text geometry, scale, color) */
class FontBuf {
/**
* @param {AtlasSDF} sdfs font atlas data associated with this font's SDFs
*/
constructor(sdfs, dynamic_scale, color) {
this.sdfs = sdfs;
this.dynamic_scale = dynamic_scale;
this.color = color;
this.z = -0.2;
this.text_vbuf_pos = [];
this.text_vbuf_uv = [];
}
drawText(str, x, y, align) {
const { sdfs } = this;
const fontsize = SDF_FONT_SIZE;
const buf = fontsize / 8;
const width = fontsize + buf * 2; // glyph width
const height = fontsize + buf * 2; // glyph height
const bx = 0; // bearing x
const scale = this.dynamic_scale / fontsize;
const lineWidth = str.length * fontsize * scale;
const pen = { x, y };
if (align == ALIGN_CENTER) {
pen.x -= (str.split('').reduce((a, c) => a + sdfs[c].glyph.glyphAdvance, 0) / 2) * scale;
}
for (let i = 0; i < str.length; i++) {
const posX = sdfs[str[i]].x; // pos in sprite x
const posY = sdfs[str[i]].y; // pos in sprite y
const advance = sdfs[str[i]].glyph.glyphAdvance;
const by = sdfs[str[i]].glyph.glyphTop - (fontsize / 2 + buf); // bearing y
this.text_vbuf_pos.push(
pen.x + ((bx - buf) * scale) , pen.y - by * scale , this.z,
pen.x + ((bx - buf + width) * scale), pen.y - by * scale , this.z,
pen.x + ((bx - buf) * scale) , pen.y + (height - by) * scale, this.z,
pen.x + ((bx - buf + width) * scale), pen.y - by * scale , this.z,
pen.x + ((bx - buf) * scale) , pen.y + (height - by) * scale, this.z,
pen.x + ((bx - buf + width) * scale), pen.y + (height - by) * scale, this.z
);
this.text_vbuf_uv.push(
posX, posY,
posX + width, posY,
posX, posY + height,
posX + width, posY,
posX, posY + height,
posX + width, posY + height
);
pen.x = pen.x + advance * scale;
}
}
clear() {
this.text_vbuf_pos = [];
this.text_vbuf_uv = [];
}
}
class TextRenderer {
constructor(gl) {
this.pMatrix = mat4_create();
/* maps character to location in spritesheet/font_atlas */
this.sdfs = {};
this.font_atlas = gl.createTexture();
this.font_bufs = [];
this.buf = {
text_vbuf_pos: gl.createBuffer(),
text_vbuf_uv: gl.createBuffer()
};
/* compile shaders */
{
const vs_text = `
attribute vec3 a_pos;
attribute vec2 a_texcoord;
uniform mat4 u_matrix;
uniform vec2 u_texsize;
varying vec2 v_texcoord;
void main() {
gl_Position = u_matrix * vec4(a_pos.xyz, 1);
v_texcoord = a_texcoord / u_texsize;
}`;
const fs_text = `
precision mediump float;
uniform sampler2D u_texture;
uniform vec4 u_color;
uniform float u_buffer;
uniform float u_gamma;
varying vec2 v_texcoord;
void main() {
float dist = texture2D(u_texture, v_texcoord).r;
float alpha = smoothstep(u_buffer - u_gamma, u_buffer + u_gamma, dist);
gl_FragColor = vec4(u_color.rgb, alpha * u_color.a);
}`;
function createProgram(gl, vertexSource, fragmentSource) {
function createShader(gl, type, source) {
const shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
throw new Error(gl.getShaderInfoLog(shader));
}
return shader;
}
const program = gl.createProgram();
const vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexSource);
const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fragmentSource);
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
throw new Error(gl.getProgramInfoLog(program));
}
const wrapper = {program};
const numAttributes = gl.getProgramParameter(program, gl.ACTIVE_ATTRIBUTES);
for (let i = 0; i < numAttributes; i++) {
const attribute = gl.getActiveAttrib(program, i);
wrapper[attribute.name] = gl.getAttribLocation(program, attribute.name);
}
const numUniforms = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
for (let i = 0; i < numUniforms; i++) {
const uniform = gl.getActiveUniform(program, i);
wrapper[uniform.name] = gl.getUniformLocation(program, uniform.name);
}
return wrapper;
}
this.shaders = {
text: createProgram(gl, vs_text, fs_text),
}
}
/* mapbox's TinySDF - https://github.com/mapbox/tiny-sdf */
let TinySDF;
{
const INF = 1e20;
class _TinySDF {
constructor({
fontSize = 24,
buffer = 3,
radius = 8,
cutoff = 0.25,
fontFamily = 'sans-serif',
fontWeight = 'normal',
fontStyle = 'normal'
} = {}) {
this.buffer = buffer;
this.cutoff = cutoff;
this.radius = radius;
// make the canvas size big enough to both have the specified buffer around the glyph
// for "halo", and account for some glyphs possibly being larger than their font size
const size = this.size = fontSize + buffer * 4;
const canvas = this._createCanvas(size);
const ctx = this.ctx = canvas.getContext('2d', {willReadFrequently: true});
ctx.font = `${fontStyle} ${fontWeight} ${fontSize}px ${fontFamily}`;
ctx.textBaseline = 'alphabetic';
ctx.textAlign = 'left'; // Necessary so that RTL text doesn't have different alignment
ctx.fillStyle = 'black';
// temporary arrays for the distance transform
this.gridOuter = new Float64Array(size * size);
this.gridInner = new Float64Array(size * size);
this.f = new Float64Array(size);
this.z = new Float64Array(size + 1);
this.v = new Uint16Array(size);
}
_createCanvas(size) {
const canvas = document.createElement('canvas');
canvas.width = canvas.height = size;
return canvas;
}
draw(char) {
const {
width: glyphAdvance,
actualBoundingBoxAscent,
actualBoundingBoxDescent,
actualBoundingBoxLeft,
actualBoundingBoxRight
} = this.ctx.measureText(char);
// The integer/pixel part of the top alignment is encoded in metrics.glyphTop
// The remainder is implicitly encoded in the rasterization
const glyphTop = Math.ceil(actualBoundingBoxAscent);
const glyphLeft = 0;
// If the glyph overflows the canvas size, it will be clipped at the bottom/right
const glyphWidth = Math.max(0, Math.min(this.size - this.buffer, Math.ceil(actualBoundingBoxRight - actualBoundingBoxLeft)));
const glyphHeight = Math.min(this.size - this.buffer, glyphTop + Math.ceil(actualBoundingBoxDescent));
const width = glyphWidth + 2 * this.buffer;
const height = glyphHeight + 2 * this.buffer;
const len = Math.max(width * height, 0);
const data = new Uint8ClampedArray(len);
const glyph = {data, width, height, glyphWidth, glyphHeight, glyphTop, glyphLeft, glyphAdvance};
if (glyphWidth === 0 || glyphHeight === 0) return glyph;
const {ctx, buffer, gridInner, gridOuter} = this;
ctx.clearRect(buffer, buffer, glyphWidth, glyphHeight);
ctx.fillText(char, buffer, buffer + glyphTop);
const imgData = ctx.getImageData(buffer, buffer, glyphWidth, glyphHeight);
// Initialize grids outside the glyph range to alpha 0
gridOuter.fill(INF, 0, len);
gridInner.fill(0, 0, len);
for (let y = 0; y < glyphHeight; y++) {
for (let x = 0; x < glyphWidth; x++) {
const a = imgData.data[4 * (y * glyphWidth + x) + 3] / 255; // alpha value
if (a === 0) continue; // empty pixels
const j = (y + buffer) * width + x + buffer;
if (a === 1) { // fully drawn pixels
gridOuter[j] = 0;
gridInner[j] = INF;
} else { // aliased pixels
const d = 0.5 - a;
gridOuter[j] = d > 0 ? d * d : 0;
gridInner[j] = d < 0 ? d * d : 0;
}
}
}
edt(gridOuter, 0, 0, width, height, width, this.f, this.v, this.z);
edt(gridInner, buffer, buffer, glyphWidth, glyphHeight, width, this.f, this.v, this.z);
for (let i = 0; i < len; i++) {
const d = Math.sqrt(gridOuter[i]) - Math.sqrt(gridInner[i]);
data[i] = Math.round(255 - 255 * (d / this.radius + this.cutoff));
}
return glyph;
}
}
// 2D Euclidean squared distance transform by Felzenszwalb & Huttenlocher https://cs.brown.edu/~pff/papers/dt-final.pdf
function edt(data, x0, y0, width, height, gridSize, f, v, z) {
for (let x = x0; x < x0 + width; x++) edt1d(data, y0 * gridSize + x, gridSize, height, f, v, z);
for (let y = y0; y < y0 + height; y++) edt1d(data, y * gridSize + x0, 1, width, f, v, z);
}
// 1D squared distance transform
function edt1d(grid, offset, stride, length, f, v, z) {
v[0] = 0;
z[0] = -INF;
z[1] = INF;
f[0] = grid[offset];
for (let q = 1, k = 0, s = 0; q < length; q++) {
f[q] = grid[offset + q * stride];
const q2 = q * q;
do {
const r = v[k];
s = (f[q] - f[r] + q2 - r * r) / (q - r) / 2;
} while (s <= z[k] && --k > -1);
k++;
v[k] = q;
z[k] = s;
z[k + 1] = INF;
}
for (let q = 0, k = 0; q < length; q++) {
while (z[k + 1] < q) k++;
const r = v[k];
const qr = q - r;
grid[offset + q * stride] = f[r] + qr * qr;
}
}
TinySDF = _TinySDF;
}
const FONT_SIZE = 40;
const FONT_NAME = "GraphLabelFont";
const font = new FontFace(
FONT_NAME,
"url(AvenirNext_Variable.ttf)",
{ weight: "bold" }
);
/* invoke now-established TinySDF in a for loop to make the font atlas */
return font.load().then(() => {
document.fonts.add(font);
/* use tiny sdf + a for loop to get a texture atlas canvas */
let sdfImage;
{
const chars = ' abcdefghijklmnopqrstuvwxyzZABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%^&*()1234567890<,>./?;:\'"\\|{}[]';
const fontCanvas = document.createElement('canvas');
fontCanvas.width = fontCanvas.height = 1024
const ctx = fontCanvas.getContext('2d');
// Convert alpha-only to RGBA so we can use `putImageData` for building the composite bitmap
function makeRGBAImageData(alphaChannel, width, height) {
const imageData = ctx.createImageData(width, height);
for (let i = 0; i < alphaChannel.length; i++) {
imageData.data[4 * i + 0] = alphaChannel[i];
imageData.data[4 * i + 1] = alphaChannel[i];
imageData.data[4 * i + 2] = alphaChannel[i];
imageData.data[4 * i + 3] = 255;
}
return imageData;
}
const charWidths = Array.from({ length: chars.length }, _ => 0);
ctx.clearRect(0, 0, fontCanvas.width, fontCanvas.height);
const fontSize = +SDF_FONT_SIZE;
const buffer = Math.ceil(fontSize / 8);
const radius = Math.ceil(fontSize / 3);
const sdf = new TinySDF({fontSize, buffer, radius, fontFamily: FONT_NAME });
const size = fontSize + buffer * 2;
const now = performance.now();
let i = 0;
for (let y = 0; y + size <= fontCanvas.height && i < chars.length; y += size) {
for (let x = 0; x + size <= fontCanvas.width && i < chars.length; x += size) {
const glyph = sdf.draw(chars[i]);
const {data, width, height} = glyph;
delete glyph.data;
this.sdfs[chars[i]] = { x, y, glyph };
ctx.putImageData(makeRGBAImageData(data, width, height), x, y);
i++;
}
}
console.log(`${i} characters (${fontSize}px, with ${buffer}px buffer) rendered in ${Math.round(performance.now() - now)}ms.`)
sdfImage = ctx.getImageData(0, 0, fontCanvas.width, fontCanvas.height);
}
/* upload that canvas to a texture */
{
gl.useProgram(this.shaders.text.program);
gl.enableVertexAttribArray(this.shaders.text.a_pos);
gl.enableVertexAttribArray(this.shaders.text.a_texcoord);
const sdfBytes = new Uint8Array(sdfImage.data)
gl.bindTexture(gl.TEXTURE_2D, this.font_atlas);
gl.texImage2D(
/* target */ gl.TEXTURE_2D,
/* level */ 0,
/* internalformat */ gl.RGBA,
/* width */ sdfImage.width,
/* height */ sdfImage.height,
/* border, */ 0,
/* format, */ gl.RGBA,
/* type, */ gl.UNSIGNED_BYTE,
/* data */ sdfBytes
);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.uniform2f(this.shaders.text.u_texsize, sdfImage.width, sdfImage.height);
}
return this;
})
}
/**
* @param scale {Number} size of text vertically in pixels
*/
useFont(scale, color) {
const fb = new FontBuf(this.sdfs, scale, color);
this.font_bufs.push(fb);
return fb;
}
clear() {
for (const font_buf of this.font_bufs) {
font_buf.clear();
}
}
render(gl) {
const pMatrix = mat4_ortho(this.pMatrix, 0, gl.canvas.width, gl.canvas.height, 0, 1, -1);
gl.viewport(
0,
0,
gl.canvas.width,
gl.canvas.height
);
gl.useProgram(this.shaders.text.program);
/* set up premultiplied alpha */
gl.blendFuncSeparate(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA, gl.ONE, gl.ONE);
gl.enable(gl.BLEND);
for (const fb of this.font_bufs) {
const gamma = 2;
gl.uniformMatrix4fv(this.shaders.text.u_matrix, false, pMatrix);
gl.uniform4fv(this.shaders.text.u_color, fb.color);
gl.uniform1f(this.shaders.text.u_buffer, 0.75);
gl.uniform1f(this.shaders.text.u_gamma, gamma * 1.4142 / fb.dynamic_scale);
/* upload/bind geometry */
const vbuf_count = fb.text_vbuf_pos.length / 3;
{
gl.bindBuffer(gl.ARRAY_BUFFER, this.buf.text_vbuf_pos);
gl.vertexAttribPointer(this.shaders.text.a_pos, 3, gl.FLOAT, false, 0, 0);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(fb.text_vbuf_pos), gl.STATIC_DRAW);
gl.bindBuffer(gl.ARRAY_BUFFER, this.buf.text_vbuf_uv);
gl.vertexAttribPointer(this.shaders.text.a_texcoord, 2, gl.FLOAT, false, 0, 0);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(fb.text_vbuf_uv), gl.STATIC_DRAW);
}
/* bind texture */
{
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, this.font_atlas);
gl.uniform1i(this.shaders.text.u_texture, 0);
}
gl.drawArrays(gl.TRIANGLES, 0, vbuf_count);
}
}
}
(async () => {
const canvas = document.getElementById('glcanvas');
const gl = canvas.getContext('webgl', {antialias: false});
if (!gl) { alert('Failed to initialize WebGL'); }
(window.onresize = () => {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
/* account for e.g. high-retina macbook screens */
if (window.devicePixelRatio > 1) {
canvas.style.width = `${canvas.width}px`;
canvas.style.height = `${canvas.height}px`;
canvas.width *= window.devicePixelRatio;
canvas.height *= window.devicePixelRatio;
}
})();
const tr = await new TextRenderer(gl);
const fonts = {
title: tr.useFont(125, [0.50, 0.25, 0.35, 1]),
subheading: tr.useFont( 50, [0.40, 0.25, 0.55, 1]),
};
requestAnimationFrame(function frame(timestamp) {
requestAnimationFrame(frame);
/* clear all */
gl.clearColor(0.93, 0.9, 0.89, 1);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
tr.clear();
{
const title_x = canvas.width /2;
const title_y = canvas.height/2;
fonts.title.drawText(
'accelerated instance graph',
title_x,
title_y - fonts.title.dynamic_scale*0.6,
ALIGN_CENTER
);
for (let i = 0; i < 20; i++) {
const x = title_x + Math.cos(Math.PI*2 * i/20 + Date.now()*0.0001) * 900;
const y = title_y + Math.sin(Math.PI*2 * i/20 + Date.now()*0.0001) * 900;
fonts.subheading.drawText("hi", x, y - fonts.subheading.dynamic_scale*0.6, ALIGN_CENTER);
}
}
tr.render(gl, canvas);
})
})()
</script>
</body>
</html>