1 2function LinearCanvasGradient(x1, y1, x2, y2) { 3 this._shader = null; 4 this._colors = []; 5 this._pos = []; 6 7 this.addColorStop = function(offset, color) { 8 if (offset < 0 || offset > 1 || !isFinite(offset)) { 9 throw 'offset must be between 0 and 1 inclusively'; 10 } 11 12 color = parseColor(color); 13 // From the spec: If multiple stops are added at the same offset on a 14 // gradient, then they must be placed in the order added, with the first 15 // one closest to the start of the gradient, and each subsequent one 16 // infinitesimally further along towards the end point (in effect 17 // causing all but the first and last stop added at each point to be 18 // ignored). 19 // To implement that, if an offset is already in the list, 20 // we just overwrite its color (since the user can't remove Color stops 21 // after the fact). 22 var idx = this._pos.indexOf(offset); 23 if (idx !== -1) { 24 this._colors[idx] = color; 25 } else { 26 // insert it in sorted order 27 for (idx = 0; idx < this._pos.length; idx++) { 28 if (this._pos[idx] > offset) { 29 break; 30 } 31 } 32 this._pos .splice(idx, 0, offset); 33 this._colors.splice(idx, 0, color); 34 } 35 } 36 37 this._copy = function() { 38 var lcg = new LinearCanvasGradient(x1, y1, x2, y2); 39 lcg._colors = this._colors.slice(); 40 lcg._pos = this._pos.slice(); 41 return lcg; 42 } 43 44 this._dispose = function() { 45 if (this._shader) { 46 this._shader.delete(); 47 this._shader = null; 48 } 49 } 50 51 this._getShader = function(currentTransform) { 52 // From the spec: "The points in the linear gradient must be transformed 53 // as described by the current transformation matrix when rendering." 54 var pts = [x1, y1, x2, y2]; 55 CanvasKit.SkMatrix.mapPoints(currentTransform, pts); 56 var sx1 = pts[0]; 57 var sy1 = pts[1]; 58 var sx2 = pts[2]; 59 var sy2 = pts[3]; 60 61 this._dispose(); 62 this._shader = CanvasKit.MakeLinearGradientShader([sx1, sy1], [sx2, sy2], 63 this._colors, this._pos, CanvasKit.TileMode.Clamp); 64 return this._shader; 65 } 66}