1// Adds compile-time JS functions to augment the CanvasKit interface.
2// Specifically, anything that should only be on the GPU version of canvaskit.
3(function(CanvasKit){
4    CanvasKit._extraInitializations = CanvasKit._extraInitializations || [];
5    CanvasKit._extraInitializations.push(function() {
6      function get(obj, attr, defaultValue) {
7        if (obj && obj.hasOwnProperty(attr)) {
8          return obj[attr];
9        }
10        return defaultValue;
11      }
12
13      function makeWebGLContext(canvas, attrs) {
14        // These defaults come from the emscripten _emscripten_webgl_create_context
15        var contextAttributes = {
16          'alpha': get(attrs, 'alpha', 1),
17          'depth': get(attrs, 'depth', 1),
18          'stencil': get(attrs, 'stencil', 0),
19          'antialias': get(attrs, 'antialias', 1),
20          'premultipliedAlpha': get(attrs, 'premultipliedAlpha', 1),
21          'preserveDrawingBuffer': get(attrs, 'preserveDrawingBuffer', 0),
22          'preferLowPowerToHighPerformance': get(attrs, 'preferLowPowerToHighPerformance', 0),
23          'failIfMajorPerformanceCaveat': get(attrs, 'failIfMajorPerformanceCaveat', 0),
24          'majorVersion': get(attrs, 'majorVersion', 1),
25          'minorVersion': get(attrs, 'minorVersion', 0),
26          'enableExtensionsByDefault': get(attrs, 'enableExtensionsByDefault', 1),
27          'explicitSwapControl': get(attrs, 'explicitSwapControl', 0),
28          'renderViaOffscreenBackBuffer': get(attrs, 'renderViaOffscreenBackBuffer', 0),
29        };
30        if (!canvas) {
31          SkDebug('null canvas passed into makeWebGLContext');
32          return 0;
33        }
34        // This check is from the emscripten version
35        if (contextAttributes['explicitSwapControl']) {
36          SkDebug('explicitSwapControl is not supported');
37          return 0;
38        }
39        return GL.createContext(canvas, contextAttributes);
40      }
41
42      // arg can be of types:
43      //  - String - in which case it is interpreted as an id of a
44      //          canvas element.
45      //  - HTMLCanvasElement - in which the provided canvas element will
46      //          be used directly.
47      //  - int - in which case it will be used as a WebGLContext. Only 1.0
48      //          contexts are known to work for now.
49      // Width and height can be provided to override those on the canvas
50      // element, or specify a height for when a context is provided.
51      CanvasKit.MakeWebGLCanvasSurface = function(arg, width, height) {
52        var ctx = arg;
53        // ctx is only > 0 if it's an int, and thus a valid context
54        if (!(ctx > 0)) {
55          var canvas = arg;
56          if (canvas.tagName !== 'CANVAS') {
57            canvas = document.getElementById(arg);
58            if (!canvas) {
59              throw 'Canvas with id ' + arg + ' was not found';
60            }
61          }
62          // we are ok with all the defaults
63          ctx = makeWebGLContext(canvas);
64        }
65
66        if (!ctx || ctx < 0) {
67          throw 'failed to create webgl context: err ' + ctx;
68        }
69
70        if (!canvas && (!width || !height)) {
71          throw 'height and width must be provided with context';
72        }
73
74        // Maybe better to use clientWidth/height.  See:
75        // https://webglfundamentals.org/webgl/lessons/webgl-anti-patterns.html
76        var surface = this._getWebGLSurface(ctx, width || canvas.width,
77                                            height || canvas.height);
78        if (!surface) {
79          SkDebug('falling back from GPU implementation to a SW based one');
80          return CanvasKit.MakeSWCanvasSurface(arg);
81        }
82        return surface;
83      };
84      // Default to trying WebGL first.
85      CanvasKit.MakeCanvasSurface = CanvasKit.MakeWebGLCanvasSurface;
86    });
87}(Module)); // When this file is loaded in, the high level object is "Module";
88