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Check for the will-change: 'transform' background image performance hack #6

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Merged
kabel merged 1 commit into from
May 31, 2016
Merged

Check for the will-change: 'transform' background image performance hack #6

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5 changes: 3 additions & 2 deletions HTMLCS.js
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Original file line number Diff line number Diff line change
Expand Up @@ -671,14 +671,15 @@ var HTMLCS = new function()
*
* @returns {Object}
*/
this.style = function(element) {
this.style = function(element, pseudo) {
var computedStyle = null;
var window = this.getElementWindow(element);
var pseudo = pseudo || null;

if (element.currentStyle) {
computedStyle = element.currentStyle;
} else if (window.getComputedStyle) {
computedStyle = window.getComputedStyle(element, null);
computedStyle = window.getComputedStyle(element, pseudo);
}

return computedStyle;
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17 changes: 17 additions & 0 deletions Standards/WCAG2AAA/Sniffs/Principle1/Guideline1_4/1_4_3_Contrast.js
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Expand Up @@ -98,6 +98,23 @@ var HTMLCS_WCAG2AAA_Sniffs_Principle1_Guideline1_4_1_4_3_Contrast = {
if (parentStyle.position == 'absolute') {
isAbsolute = true;
}

//Search for the smooth scrolling willChange: 'transform' background hack
//See http://fourkitchens.com/blog/article/fix-scrolling-performance-css-will-change-property
var beforeStyle = HTMLCS.util.style(parent, ':before');
if (
beforeStyle
&& beforeStyle.position == 'fixed'
&& beforeStyle.willChange == 'transform'
//Make sure it is trying to cover the entire content area
&& beforeStyle.width == parentStyle.width
&& parseInt(beforeStyle.height, 10) <= parseInt(parentStyle.height, 10)
//And finally it needs a background image
&& beforeStyle.backgroundImage !== 'none'
) {
hasBgImg = true;
break;
}

parent = parent.parentNode;
}//end while
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