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: 400px;
    height: 600px;
  }
  #choice {
    border: 1px solid blue;
    box-sizing: border-box;
    width: 400px;
    height: 400px;
    padding: 10px;
    font-size: 3em;
    display: flex;
    flex-direction: column;
  }
  #choice label {
    display: flex;
    align-items: center;
    gap: 0.3em;
  }
  #choice input[type="radio"] {
    width: 0.8em;
    height: 0.8em;
  }
  #choice button {
    font-size: 0.5em;
    margin-top: 0.4em;
    padding: 0.2em 0.6em;
  }
  .message {
    border: 1px solid blue;
    box-sizing: border-box;
    width: 400px;
    height: 400px;
    padding: 10px;
    font-size: 2em;
    display: flex;
    flex-direction: column;
  }
  .message button {
    font-size: 0.5em;
    margin-top: 0.4em;
    padding: 0.2em 0.6em;
  }
</style>

<!-- Note: content=drawable is the new API and layoutsubtree has been left -->
<!-- only for temporary backwards compatibility. -->
<canvas id="gl-canvas" width="400" height="600" content="drawable" layoutsubtree>
  <div drawable id="choice">
    <label><input type="radio" id="chk-english" name="language" value="english" checked> English</label>
    <label><input type="radio" id="chk-spanish" name="language" value="spanish"> Español</label>
    <label><input type="radio" id="chk-hindi" name="language" value="hindi"> हिंदी</label>
    <label><input type="radio" id="chk-korean" name="language" value="korean"> 한국어</label>
    <button id="flip-btn" onclick="flip()">Flip</button>
  </div>
  <div drawable id="english" class="message" inert>
    <p lang="en">Internationalized text made easy with HTML-in-Canvas</p>
    <button onclick="flip()">Flip</button>
  </div>
  <div drawable id="spanish" class="message" inert>
    <p lang="es">Texto internacionalizado hecho fácil con HTML-in-Canvas</p>
    <button onclick="flip()">Flip</button>
  </div>
  <div drawable id="hindi" class="message" inert>
    <p lang="hi">HTML-in-Canvas के साथ अंतर्राष्ट्रीयकृत पाठ आसान बना</p>
    <button onclick="flip()">Flip</button>
  </div>
  <div drawable id="korean" class="message" inert>
    <p lang="ko">HTML-in-Canvas로 쉬워진 국제화 텍스트</p>
    <button onclick="flip()">Flip</button>
  </div>
</canvas>

<script>
  let canvas_css_width = 400;
  let canvas_css_height = 600;
  let choice_in_front = true;
  let card_rotation = 0.0;
  let cardTargetRotation = 0.0;
  let currentTime = 0;
  let deltaTime = 0;
  let render_context = null;

  // Determine which element texture is visible
  function getVisibleElement() {
    if (cardTargetRotation > 0.0) {
      choice_in_front = false;
      var checked_elmt = document.querySelector('input[name="language"]:checked');
      return document.getElementById(checked_elmt.value);
    } else {
      choice_in_front = true;
      return document.getElementById("choice");
    }
  }

  // Update the inert status when the card is flipped. This keeps the
  // accessibility information up to date and determines which elements are
  // hit tested.
  function setInert() {
    const messages = ["english", "spanish", "hindi", "korean"];
    var visible_element = getVisibleElement();
    var choice_elmt = document.getElementById("choice");
    if (choice_elmt == visible_element) {
      choice_elmt.removeAttribute("inert");
    } else {
      choice_elmt.setAttribute("inert", true);
    }
    for (id in messages) {
      var elmt = document.getElementById(messages[id]);
      if (elmt == visible_element) {
        elmt.removeAttribute("inert");
      } else {
        elmt.setAttribute("inert", true);
      }
    }
  }

  // Flip the card, which involves triggering the animation and resetting the
  // inert status of elements.
  function flip() {
    if (cardTargetRotation > 0.0) {
      cardTargetRotation = 0.0;
    } else {
      cardTargetRotation = Math.PI;
    }
    setInert();
  }

  function updateElementGeometry(model_to_screen_matrix) {
    var top_left = vec4.fromValues(-1, -1, 0.1, 1);
    var bottom_right = vec4.fromValues(1, 1, 0.1, 1);
    vec4.transformMat4(top_left, top_left, model_to_screen_matrix);
    vec4.transformMat4(bottom_right, bottom_right, model_to_screen_matrix);
    var gl_screen_rect = new DOMRect();
    gl_screen_rect.x = top_left[0] / top_left[3];
    gl_screen_rect.y = top_left[1] / top_left[3];
    gl_screen_rect.width = bottom_right[0] / bottom_right[3] - gl_screen_rect.x;
    gl_screen_rect.height = bottom_right[1] / bottom_right[3] - gl_screen_rect.y;

    // The GL rectangle origin (-1,-1) size (2,2) covers the canvas area. Map
    // GL coordinates into canvas CSS coordinates.
    const canvas = document.querySelector('#gl-canvas');
    var canvas_rect = new DOMRect();
    canvas_rect.x = (gl_screen_rect.x + 1) * canvas_css_width / 2;
    canvas_rect.y = (gl_screen_rect.y + 1) * canvas_css_height / 2;
    canvas_rect.width = gl_screen_rect.width * canvas_css_width / 2;
    canvas_rect.height = gl_screen_rect.height * canvas_css_height / 2;

    // Determine the DOMMatrix transform that maps the element bounding box
    // onto the GL rect for the texture area. The element bounding box is
    // 400x400.
    var visible_elmt = getVisibleElement();
    var canvas_transform = new DOMMatrix();
    canvas_transform.a = canvas_rect.width / 400;
    canvas_transform.d = canvas_rect.height / 400;
    canvas_transform.e = canvas_rect.x;
    canvas_transform.f = canvas_rect.y;

    if (canvas.updateElementGeometry !== undefined) {
      // New html-in-canvas approach for updating the element's geometry from
      // the canvas transform.
      canvas.updateElementGeometry(visible_elmt, {canvasTransform: canvas_transform});
    } else {
      // Older approach (do not use).
      visible_elmt.style.transform = canvas_transform.toString();
    }
  }

  // Create an initial empty texture for binding.
  function createEmptyTexture(gl) {
    const texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);

    // 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/update the element's visual onto the specified texture
  function updateTexture(gl, texture, element) {
    gl.bindTexture(gl.TEXTURE_2D, texture);
    const internalFormat = gl.RGBA8;

    try {
      // Pre-allocate texture backing with pre-determined size.
      let elementImage = gl.canvas.captureElementImage(element);
      gl.texImage2D(
          /* target */ gl.TEXTURE_2D,
          /* level */ 0,
          /* internalformat */ gl.RGBA8,
          /* width */ elementImage.width,
          /* height */ elementImage.height,
          /* border */ 0,
          /* format */ gl.RGBA,
          /* type */ gl.UNSIGNED_BYTE,
          /* srcData */ null);
      gl.texElementSubImage2D(gl.TEXTURE_2D, /*level*/0, /*xoffset*/0, /*yoffset*/0, element);
    } catch (e) {
      try {
        // The texElementImage2D API was recently changed (see:
        // https://github.com/WICG/html-in-canvas#idl-changes). This snippet
        // supports the old syntax temporarily so that the demos do not break.
        const level = 0;
        const srcFormat = gl.RGBA;
        const destType = gl.UNSIGNED_BYTE;
        gl.texElementImage2D(gl.TEXTURE_2D, level, internalFormat,
                                srcFormat, destType, element);
        console.log('Note: using old texElementImage2D API');
      } catch (e) {
        // The texElementImage2D API was recently changed (see:
        // https://github.com/WICG/html-in-canvas#idl-changes). This snippet
        // supports the old syntax temporarily so that the demos do not break.
        gl.texElementImage2D(gl.TEXTURE_2D, internalFormat, element);
        console.log('Note: using old texElementImage2D API');
      }
    }
  }

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

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

    var model_to_screen_matrix = drawScene(render_context.gl,
                                           render_context.program,
                                           render_context.buffers,
                                           render_context.texture_checkboxes,
                                           render_context.texture_choice,
                                           card_rotation);

    updateElementGeometry(model_to_screen_matrix);

    if (card_rotation < cardTargetRotation) {
      card_rotation += deltaTime;
      if (card_rotation > cardTargetRotation) {
        card_rotation = cardTargetRotation;
      }
    } else if (card_rotation > cardTargetRotation) {
      card_rotation -= deltaTime;
      if (card_rotation < cardTargetRotation) {
        card_rotation = cardTargetRotation;
      }
    }
  }

  function setupGL() {
    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);
      }
    `;

    const shaderProgram = initShaderProgram(gl, vsSource, fsSource);

    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);

    // Initialize textures without drawing immediately, waiting for onpaint to fill them
    const texture_checkboxes = createEmptyTexture(gl);
    const texture_choice = createEmptyTexture(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_checkboxes: texture_checkboxes,
      texture_choice: texture_choice,
    };
  }

  onload = () => {
    const canvas = document.querySelector('#gl-canvas');
    let initialized_gl = false;
    let lastLangId = null;

    // The main paint event loop.
    canvas.onpaint = (event) => {
      if (!initialized_gl) {
        setupGL();
        initialized_gl = true;
      }

      if (event.changedElements && event.changedElements.length) {
        // Convert elements into an array if they are not already to safely use array methods
        const changedArray = Array.from(event.changedElements);
        const choiceEl = document.getElementById("choice");
        const checkedLang = document.querySelector('input[name="language"]:checked');
        const langId = checkedLang ? checkedLang.value : "english";
        const langEl = document.getElementById(langId);

        // Update the checkboxes texture if the choice element changed
        if (changedArray.includes(choiceEl)) {
          updateTexture(render_context.gl, render_context.texture_checkboxes, choiceEl);
        }

        // Update the choice texture if its content changed, or if the user selected a new language
        if (changedArray.includes(langEl) || langId !== lastLangId) {
          updateTexture(render_context.gl, render_context.texture_choice, langEl);
          lastLangId = langId;
        }
      }

      render();

      // Loop to continuously fire canvas paint events.
      canvas.requestPaint();
    }
    canvas.requestPaint();

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