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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        var contextAttributes = {
15          alpha: get(attrs, 'alpha', 1),
16          depth: get(attrs, 'depth', 1),
17          stencil: get(attrs, 'stencil', 8),
18          antialias: get(attrs, 'antialias', 1),
19          premultipliedAlpha: get(attrs, 'premultipliedAlpha', 1),
20          preserveDrawingBuffer: get(attrs, 'preserveDrawingBuffer', 0),
21          preferLowPowerToHighPerformance: get(attrs, 'preferLowPowerToHighPerformance', 0),
22          failIfMajorPerformanceCaveat: get(attrs, 'failIfMajorPerformanceCaveat', 0),
23          majorVersion: get(attrs, 'majorVersion', 2),
24          minorVersion: get(attrs, 'minorVersion', 0),
25          enableExtensionsByDefault: get(attrs, 'enableExtensionsByDefault', 1),
26          explicitSwapControl: get(attrs, 'explicitSwapControl', 0),
27          renderViaOffscreenBackBuffer: get(attrs, 'renderViaOffscreenBackBuffer', 0),
28        };
29        if (!canvas) {
30          SkDebug('null canvas passed into makeWebGLContext');
31          return 0;
32        }
33        // This check is from the emscripten version
34        if (contextAttributes['explicitSwapControl']) {
35          SkDebug('explicitSwapControl is not supported');
36          return 0;
37        }
38        // GL is an enscripten provided helper
39        // See https://github.com/emscripten-core/emscripten/blob/incoming/src/library_webgl.js
40        var ctx = GL.createContext(canvas, contextAttributes);
41
42        if (!ctx && contextAttributes.majorVersion > 1) {
43          contextAttributes.majorVersion = 1;  // fall back to WebGL 1.0
44          contextAttributes.minorVersion = 0;
45          ctx = GL.createContext(canvas, contextAttributes);
46        }
47        return ctx;
48      }
49
50      CanvasKit.GetWebGLContext = function(canvas, attrs) {
51        return makeWebGLContext(canvas, attrs);
52      };
53
54      // arg can be of types:
55      //  - String - in which case it is interpreted as an id of a
56      //          canvas element.
57      //  - HTMLCanvasElement - in which the provided canvas element will
58      //          be used directly.
59      // Width and height can be provided to override those on the canvas
60      // element, or specify a height for when a context is provided.
61      CanvasKit.MakeWebGLCanvasSurface = function(arg, width, height) {
62        var canvas = arg;
63        if (canvas.tagName !== 'CANVAS') {
64          canvas = document.getElementById(arg);
65          if (!canvas) {
66            throw 'Canvas with id ' + arg + ' was not found';
67          }
68        }
69        // we are ok with all the defaults
70        var ctx = this.GetWebGLContext(canvas);
71
72        if (!ctx || ctx < 0) {
73          throw 'failed to create webgl context: err ' + ctx;
74        }
75
76        if (!canvas && (!width || !height)) {
77          throw 'height and width must be provided with context';
78        }
79
80        var grcontext = this.MakeGrContext(ctx);
81
82        if (grcontext) {
83           // Bump the default resource cache limit.
84          var RESOURCE_CACHE_BYTES = 256 * 1024 * 1024;
85          grcontext.setResourceCacheLimitBytes(RESOURCE_CACHE_BYTES);
86        }
87
88
89        // Maybe better to use clientWidth/height.  See:
90        // https://webglfundamentals.org/webgl/lessons/webgl-anti-patterns.html
91        var surface = this.MakeOnScreenGLSurface(grcontext,
92                                                 width  || canvas.width,
93                                                 height || canvas.height);
94        if (!surface) {
95          SkDebug('falling back from GPU implementation to a SW based one');
96          // we need to throw away the old canvas (which was locked to
97          // a webGL context) and create a new one so we can
98          var newCanvas = canvas.cloneNode(true);
99          var parent = canvas.parentNode;
100          parent.replaceChild(newCanvas, canvas);
101          // add a class so the user can detect that it was replaced.
102          newCanvas.classList.add('ck-replaced');
103
104          return CanvasKit.MakeSWCanvasSurface(newCanvas);
105        }
106        surface._context = ctx;
107        surface.grContext = grcontext;
108        return surface;
109      };
110      // Default to trying WebGL first.
111      CanvasKit.MakeCanvasSurface = CanvasKit.MakeWebGLCanvasSurface;
112    });
113}(Module)); // When this file is loaded in, the high level object is "Module";
114