experimental/skottiekit/gpu.js

(function(SkottieKit){
SkottieKit._extraInitializations = SkottieKit._extraInitializations || [];
SkottieKit._extraInitializations.push(function() {
  function get(obj, attr, defaultValue) {
    if (obj && obj.hasOwnProperty(attr)) {
      return obj[attr];
    }
    return defaultValue;
  }

  function makeWebGLContext(canvas, attrs) {
    var contextAttributes = {
      alpha: get(attrs, 'alpha', 1),
      depth: get(attrs, 'depth', 1),
      stencil: get(attrs, 'stencil', 8),
      antialias: get(attrs, 'antialias', 1),
      premultipliedAlpha: get(attrs, 'premultipliedAlpha', 1),
      preserveDrawingBuffer: get(attrs, 'preserveDrawingBuffer', 0),
      preferLowPowerToHighPerformance: get(attrs, 'preferLowPowerToHighPerformance', 0),
      failIfMajorPerformanceCaveat: get(attrs, 'failIfMajorPerformanceCaveat', 0),
      majorVersion: get(attrs, 'majorVersion', 2),
      minorVersion: get(attrs, 'minorVersion', 0),
      enableExtensionsByDefault: get(attrs, 'enableExtensionsByDefault', 1),
      explicitSwapControl: get(attrs, 'explicitSwapControl', 0),
      renderViaOffscreenBackBuffer: get(attrs, 'renderViaOffscreenBackBuffer', 0),
    };
    if (!canvas) {
      SkDebug('null canvas passed into makeWebGLContext');
      return 0;
    }
    // This check is from the emscripten version
    if (contextAttributes['explicitSwapControl']) {
      SkDebug('explicitSwapControl is not supported');
      return 0;
    }
    // GL is an enscripten provided helper
    // See https://github.com/emscripten-core/emscripten/blob/incoming/src/library_webgl.js
    var ctx = GL.createContext(canvas, contextAttributes);

    if (!ctx && contextAttributes.majorVersion > 1) {
      contextAttributes.majorVersion = 1;  // fall back to WebGL 1.0
      contextAttributes.minorVersion = 0;
      ctx = GL.createContext(canvas, contextAttributes);
    }
    return ctx;
  }

  SkottieKit.GetWebGLContext = function(canvas, attrs) {
    return makeWebGLContext(canvas, attrs);
  };

  // arg can be of types:
  //  - String - in which case it is interpreted as an id of a
  //          canvas element.
  //  - HTMLCanvasElement - in which the provided canvas element will
  //          be used directly.
  // Width and height can be provided to override those on the canvas
  // element, or specify a height for when a context is provided.
  SkottieKit.MakeWebGLCanvasSurface = function(arg, width, height) {
    var canvas = arg;
    if (canvas.tagName !== 'CANVAS') {
      canvas = document.getElementById(arg);
      if (!canvas) {
        throw 'Canvas with id ' + arg + ' was not found';
      }
    }
    // we are ok with all the defaults
    var ctx = this.GetWebGLContext(canvas);

    if (!ctx || ctx < 0) {
      throw 'failed to create webgl context: err ' + ctx;
    }

    if (!canvas && (!width || !height)) {
      throw 'height and width must be provided with context';
    }

    var grcontext = this.MakeGrContext(ctx);

    // if (grcontext) {
    //    // Bump the default resource cache limit.
    //   var RESOURCE_CACHE_BYTES = 256 * 1024 * 1024;
    //   grcontext.setResourceCacheLimitBytes(RESOURCE_CACHE_BYTES);
    // }


    // Maybe better to use clientWidth/height.  See:
    // https://webglfundamentals.org/webgl/lessons/webgl-anti-patterns.html
    var surface = this.MakeOnScreenGLSurface(grcontext,
                                             width  || canvas.width,
                                             height || canvas.height);
    if (!surface) {
      SkDebug('falling back from GPU implementation to a SW based one');
      // we need to throw away the old canvas (which was locked to
      // a webGL context) and create a new one so we can
      var newCanvas = canvas.cloneNode(true);
      var parent = canvas.parentNode;
      parent.replaceChild(newCanvas, canvas);
      // add a class so the user can detect that it was replaced.
      newCanvas.classList.add('ck-replaced');

      return SkottieKit.MakeSWCanvasSurface(newCanvas);
    }
    surface._context = ctx;
    surface.grContext = grcontext;
    return surface;
  };
  // Default to trying WebGL first.
  SkottieKit.MakeCanvasSurface = SkottieKit.MakeWebGLCanvasSurface;
});
}(Module)); // When this file is loaded in, the high level object is "Module";