66 lines
2.0 KiB
JavaScript
66 lines
2.0 KiB
JavaScript
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function LinearCanvasGradient(x1, y1, x2, y2) {
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this._shader = null;
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this._colors = [];
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this._pos = [];
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this.addColorStop = function(offset, color) {
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if (offset < 0 || offset > 1 || !isFinite(offset)) {
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throw 'offset must be between 0 and 1 inclusively';
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}
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color = parseColor(color);
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// From the spec: If multiple stops are added at the same offset on a
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// gradient, then they must be placed in the order added, with the first
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// one closest to the start of the gradient, and each subsequent one
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// infinitesimally further along towards the end point (in effect
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// causing all but the first and last stop added at each point to be
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// ignored).
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// To implement that, if an offset is already in the list,
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// we just overwrite its color (since the user can't remove Color stops
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// after the fact).
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var idx = this._pos.indexOf(offset);
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if (idx !== -1) {
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this._colors[idx] = color;
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} else {
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// insert it in sorted order
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for (idx = 0; idx < this._pos.length; idx++) {
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if (this._pos[idx] > offset) {
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break;
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}
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}
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this._pos .splice(idx, 0, offset);
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this._colors.splice(idx, 0, color);
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}
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}
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this._copy = function() {
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var lcg = new LinearCanvasGradient(x1, y1, x2, y2);
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lcg._colors = this._colors.slice();
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lcg._pos = this._pos.slice();
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return lcg;
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}
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this._dispose = function() {
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if (this._shader) {
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this._shader.delete();
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this._shader = null;
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}
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}
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this._getShader = function(currentTransform) {
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// From the spec: "The points in the linear gradient must be transformed
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// as described by the current transformation matrix when rendering."
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var pts = [x1, y1, x2, y2];
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CanvasKit.SkMatrix.mapPoints(currentTransform, pts);
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var sx1 = pts[0];
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var sy1 = pts[1];
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var sx2 = pts[2];
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var sy2 = pts[3];
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this._dispose();
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this._shader = CanvasKit.MakeLinearGradientShader([sx1, sy1], [sx2, sy2],
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this._colors, this._pos, CanvasKit.TileMode.Clamp);
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return this._shader;
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}
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}
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