optimization; avoid reading computed styles unless necessary
parent
9f1856d55b
commit
db9c346b41
21
js/reveal.js
21
js/reveal.js
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@ -1131,18 +1131,27 @@
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if( data.backgroundPosition ) contentElement.style.backgroundPosition = data.backgroundPosition;
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if( data.backgroundOpacity ) contentElement.style.opacity = data.backgroundOpacity;
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// If this slide has a background color, add a class that
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// If this slide has a background color, we add a class that
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// signals if it is light or dark. If the slide has no background
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// color, no class will be set
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var computedBackgroundStyle = window.getComputedStyle( element );
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if( computedBackgroundStyle && computedBackgroundStyle.backgroundColor ) {
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var rgb = colorToRgb( computedBackgroundStyle.backgroundColor );
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// color, no class will be added
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var contrastColor = data.backgroundColor;
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// If no bg color was found, check the computed background
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if( !contrastColor ) {
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var computedBackgroundStyle = window.getComputedStyle( element );
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if( computedBackgroundStyle && computedBackgroundStyle.backgroundColor ) {
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contrastColor = computedBackgroundStyle.backgroundColor;
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}
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}
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if( contrastColor ) {
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var rgb = colorToRgb( contrastColor );
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// Ignore fully transparent backgrounds. Some browsers return
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// rgba(0,0,0,0) when reading the computed background color of
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// an element with no background
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if( rgb && rgb.a !== 0 ) {
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if( colorBrightness( computedBackgroundStyle.backgroundColor ) < 128 ) {
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if( colorBrightness( contrastColor ) < 128 ) {
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slide.classList.add( 'has-dark-background' );
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}
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else {
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