CSS: Remove filter from style when setting opacity to 1 - Fixes #6652 - REMOVE...

CSS: Remove filter from style when setting opacity to 1 - Fixes #6652 - REMOVE FILTER:ALPHA(OPACITY=100) AFTER ANIMATION

src/css.js

@@ -2,6 +2,7 @@
 
 var ralpha = /alpha\([^)]*\)/i,
 	ropacity = /opacity=([^)]*)/,
+	rfilter = /filter:[^;]*;?/i,
 	// fixed for IE9, see #8346
 	rupper = /([A-Z]|^ms)/g,
 	rnumpx = /^-?\d+(?:px)?$/i,
@@ -211,18 +212,28 @@ if ( !jQuery.support.opacity ) {
 
 		set: function( elem, value ) {
 			var style = elem.style,
-				currentStyle = elem.currentStyle;
+				currentStyle = elem.currentStyle,
+				opacity = jQuery.isNaN( value ) ? "" : "alpha(opacity=" + value * 100 + ")",
+				filter = currentStyle && currentStyle.filter || style.filter || "";
 
 			// IE has trouble with opacity if it does not have layout
 			// Force it by setting the zoom level
 			style.zoom = 1;
 
-			// Set the alpha filter to set the opacity
-			var opacity = jQuery.isNaN( value ) ?
-				"" :
-				"alpha(opacity=" + value * 100 + ")",
-				filter = currentStyle && currentStyle.filter || style.filter || "";
+			// if setting opacity to 1, and no other filters exist - attempt to remove filter attribute #6652
+			if ( value >= 1 && jQuery.trim( filter.replace( ralpha, "" ) ) === "" ) {
+
+				// Setting style.filter to null, "" & " " still leave "filter:" in the cssText
+				// if "filter:" is present at all, clearType is disabled, we want to avoid this
+				style.cssText = style.cssText.replace( rfilter, "" );
+
+				// if there there is no filter style applied in a css rule, we are done
+				if ( currentStyle && !currentStyle.filter ) {
+					return;
+				}
+			}
 
+			// otherwise, set new filter values
 			style.filter = ralpha.test( filter ) ?
 				filter.replace( ralpha, opacity ) :
 				filter + " " + opacity;