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Revert "Fix: Add blend mode fallbacks if not supported (#758)" (#769)
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This reverts commit 95def3b.
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Jeremy Press authored Apr 12, 2018
1 parent 60e2af4 commit b80dafc
Showing 1 changed file with 0 additions and 24 deletions.
24 changes: 0 additions & 24 deletions src/lib/polyfill.js
Original file line number Diff line number Diff line change
@@ -392,28 +392,4 @@ if (!String.prototype.startsWith) {
return this.substr(!pos || pos < 0 ? 0 : +pos, search.length) === search;
};
}

// Provides a partial workaround when blend modes are not supported (IE11).
// See issue https://github.com/mozilla/pdf.js/issues/5264.
// NOTE: This is not a full blend mode polyfill, but a way to see blended content
// that would otherwise be unviewable.way to see blended content that would otherwise be unviewable.
const canvas = document.createElement('canvas');
const ctx = canvas.getContext('2d');
ctx.globalCompositeOperation = 'multiply';

// Check to see if the current browser supports globalCompositeOperation, which would be the case if the
// set value is respected.
if (ctx.globalCompositeOperation !== 'multiply') {
// Define custom behavior for blending when blend modes are not supported.
Object.defineProperty(CanvasRenderingContext2D.prototype, 'globalCompositeOperation', {
set: function(value) {
// We only manually blend if the mode is not 'source-over'
// which is the only supported blend mode that does no blending.
if (value !== 'source-over' && this.globalAlpha === 1) {
// Choose 50% to give equal visibility to top and bottom elements.
this.globalAlpha = 0.5;
}
}
});
}
/* eslint-enable */

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