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 // GL is an enscripten provided helper 40 // See https://github.com/emscripten-core/emscripten/blob/incoming/src/library_webgl.js 41 return GL.createContext(canvas, contextAttributes); 42 } 43 44 CanvasKit.GetWebGLContext = function(canvas, attrs) { 45 return makeWebGLContext(canvas, attrs); 46 }; 47 48 // arg can be of types: 49 // - String - in which case it is interpreted as an id of a 50 // canvas element. 51 // - HTMLCanvasElement - in which the provided canvas element will 52 // be used directly. 53 // Width and height can be provided to override those on the canvas 54 // element, or specify a height for when a context is provided. 55 CanvasKit.MakeWebGLCanvasSurface = function(arg, width, height) { 56 var canvas = arg; 57 if (canvas.tagName !== 'CANVAS') { 58 canvas = document.getElementById(arg); 59 if (!canvas) { 60 throw 'Canvas with id ' + arg + ' was not found'; 61 } 62 } 63 // we are ok with all the defaults 64 var ctx = CanvasKit.GetWebGLContext(canvas); 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 var grcontext = this.MakeGrContext(ctx); 75 // Maybe better to use clientWidth/height. See: 76 // https://webglfundamentals.org/webgl/lessons/webgl-anti-patterns.html 77 var surface = this.MakeOnScreenGLSurface(grcontext, 78 width || canvas.width, 79 height || canvas.height); 80 if (!surface) { 81 SkDebug('falling back from GPU implementation to a SW based one'); 82 return CanvasKit.MakeSWCanvasSurface(arg); 83 } 84 return surface; 85 }; 86 // Default to trying WebGL first. 87 CanvasKit.MakeCanvasSurface = CanvasKit.MakeWebGLCanvasSurface; 88 }); 89 }(Module)); // When this file is loaded in, the high level object is "Module"; 90
