packt-publishing-tutorials/web-development-tutorials/webgl-beginners-guide/ch1_GL_Context.html at master · learning-software-development/packt-publishing-tutorials · GitHub

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<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>WebGL Beginner's Guide - Setting up the canvas</title>
</head>

<body onLoad="getGLContext()">
  <canvas id="canvas-element-id" width="800" height="600">
    Your browser does not support HTML5
  </canvas>

  <style type="text/css">
    canvas {
      border: 2px dotted blue;
    }
  </style>

  <script>
    var gl = null;
    function getGLContext() {
      var canvas = document.getElementById("canvas-element-id");
      if (canvas == null) {
        alert("there is no canvas on this page");
        return;
      }

      var names = [
        "webgl",
        "experimental-webgl",
        "webkit-3d",
        "moz-webgl"
      ];

      for (var i = 0; i < names.length; ++i) {
        try {
          gl = canvas.getContext(names[i]);
        }
        catch (e) { }
        if (gl) break;
      }

      if (gl == null) {
        alert("WebGL is not available");
      }
      else {
        alert("Hooray! You got a WebGL context");
      }
    }
  </script>
</body>

</html>