html-in-canvas/Examples/webGL.html at main · WICG/html-in-canvas · GitHub

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<!doctype html>
<meta charset="utf-8" />
<title>Demo of complex text in WebGL</title>
<script
  src="https://cdnjs.cloudflare.com/ajax/libs/gl-matrix/2.8.1/gl-matrix-min.js"
  integrity="sha512-zhHQR0/H5SEBL3Wn6yYSaTTZej12z0hVZKOv3TwCUXT1z5qeqGcXJLLrbERYRScEDDpYIJhPC1fk31gqR783iQ=="
  crossorigin="anonymous"
  defer>
</script>
<script src="webGLSetup.js"></script>
<style>
  canvas {
    border: 1px solid blue;
    width: 638px;
    height: 318px;
  }
  #draw_element {
    border: 1px solid blue;
    width: 400px;
    height: 400px;
    padding: 10px;
  }
</style>

<canvas id="gl-canvas" width="638" height="318" layoutsubtree="true">
  <!-- inert to prevent hit testing in this example. -->
  <div id="draw_element" inert>
    Hello world!<br>I'm multi-line, <b>formatted</b>,
    rotated text with emoji (&#128512;), RTL text
    <span dir=rtl>من فارسی صحبت میکنم</span>,
    vertical text,
    <p style="writing-mode: vertical-rl;">
      这是垂直文本
    </p>
    an inline image (<img width="150" src="wolf.jpg">), and
    <svg width="50" height="50">
      <circle cx="25" cy="25" r="20" fill="green" />
      <text x="25" y="30" font-size="15" text-anchor="middle" fill="#fff">
        SVG
      </text>
    </svg>!
  </div>
</canvas>

<script>
  let cubeRotation = 0.0;
  let currentTime = 0;
  let deltaTime = 0;
  let render_context = null;

  //
  // Initialize a texture and load an image.
  // When the image finished loading copy it into the texture.
  //
  function loadTexture(gl) {
    const texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);

    const level = 0;
    const internalFormat = gl.RGBA;
    const srcFormat = gl.RGBA;
    const srcType = gl.UNSIGNED_BYTE;

    gl.texElementImage2D(gl.TEXTURE_2D, level, internalFormat,
                            srcFormat, srcType, draw_element);

    // Linear texture filtering produces better results than mipmap with text.
    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);

    return texture;
  }

  // Draw the scene repeatedly
  function render() {
    let new_time = performance.now() * 0.001; // convert to seconds
    deltaTime = new_time - currentTime;
    currentTime = new_time;

    if (render_context === null) {
      return;
    }

    drawScene(render_context.gl,
              render_context.program,
              render_context.buffers,
              render_context.texture,
              cubeRotation);

    cubeRotation += deltaTime;
    requestAnimationFrame(render);
  }

  function main() {
    const canvas = document.querySelector('#gl-canvas');
    // Initialize the GL context
    const gl = canvas.getContext('webgl2');

    // Only continue if WebGL is available and working
    if (gl === null) {
      alert(
        'Unable to initialize WebGL. Your browser or machine may not support it.',
      );
      return;
    }

    // Vertex shader program
    const vsSource = `
      attribute vec4 aVertexPosition;
      attribute vec2 aTextureCoord;

      uniform mat4 uModelViewMatrix;
      uniform mat4 uProjectionMatrix;

      varying highp vec2 vTextureCoord;

      void main(void) {
        gl_Position = uProjectionMatrix * uModelViewMatrix * aVertexPosition;
        vTextureCoord = aTextureCoord;
      }
    `;

    // Fragment shader program
    const fsSource = `
      varying highp vec2 vTextureCoord;

      uniform sampler2D uSampler;

      void main(void) {
        gl_FragColor = texture2D(uSampler, vTextureCoord);
      }
    `;

    // Initialize a shader program; this is where all the lighting
    // for the vertices and so forth is established.
    const shaderProgram = initShaderProgram(gl, vsSource, fsSource);

    // Collect all the info needed to use the shader program.
    // Look up which attribute our shader program is using
    // for aVertexPosition and look up uniform locations.
    const programInfo = {
      program: shaderProgram,
      attribLocations: {
        vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
        textureCoord: gl.getAttribLocation(shaderProgram, 'aTextureCoord'),
      },
      uniformLocations: {
        projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),
        modelViewMatrix: gl.getUniformLocation(shaderProgram, 'uModelViewMatrix'),
        uSampler: gl.getUniformLocation(shaderProgram, 'uSampler'),
      },
    };

    const buffers = initBuffers(gl);

    // Load texture
    const texture = loadTexture(gl);
    // Flip image pixels into the bottom-to-top order that WebGL expects.
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);

    render_context = {
      gl: gl,
      program: programInfo,
      buffers: buffers,
      texture:texture,
    };

    requestAnimationFrame(render);
  }

  onload = () => {
    const canvas = document.querySelector('#gl-canvas');
    canvas.onpaint = () => {
      main();
    }
    canvas.requestPaint();

    const observer = new ResizeObserver(([entry]) => {
      canvas.width = entry.devicePixelContentBoxSize[0].inlineSize;
      canvas.height = entry.devicePixelContentBoxSize[0].blockSize;
    });
    observer.observe(canvas, {box: 'device-pixel-content-box'});
  }
</script>