Detect WebGL - Web APIs 编辑

Feature-detecting WebGL

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This example demonstrates how to detect a WebGL rendering context and reports the result to the user.

In this first example we are going to check whether the browser supports WebGL. To that end we will try to obtain the WebGL rendering context from a canvas element. The WebGL rendering context is an interface, through which you can set and query the state of the graphics machine, send data to the WebGL, and execute draw commands.

Saving the state of the graphics machine within a single context interface is not unique to WebGL. This is also done in other graphics {̣{Glossary("API")}}, such as the canvas 2D rendering context. However, the properties and variables you can tweak are different for each API.

<p>[ Here would go the result of WebGL feature detection ]</p>
<button>Press here to detect WebGLRenderingContext</button>

body {
  text-align : center;
}
button {
  display : block;
  font-size : inherit;
  margin : auto;
  padding : 0.6em;
}

// Run everything inside window load event handler, to make sure
// DOM is fully loaded and styled before trying to manipulate it.
window.addEventListener("load", function() {
  var paragraph = document.querySelector("p"),
    button = document.querySelector("button");
  // Adding click event handler to button.
  button.addEventListener("click", detectWebGLContext, false);
  function detectWebGLContext () {
    // Create canvas element. The canvas is not added to the
    // document itself, so it is never displayed in the
    // browser window.
    var canvas = document.createElement("canvas");
    // Get WebGLRenderingContext from canvas element.
    var gl = canvas.getContext("webgl")
      || canvas.getContext("experimental-webgl");
    // Report the result.
    if (gl && gl instanceof WebGLRenderingContext) {
      paragraph.textContent =
        "Congratulations! Your browser supports WebGL.";
    } else {
      paragraph.textContent = "Failed to get WebGL context. "
        + "Your browser or device may not support WebGL.";
    }
  }
}, false);

The source code of this example is also available on GitHub.

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