First look at css hooks. These hooks provide a way to change how jQuery...

First look at css hooks. These hooks provide a way to change how jQuery handles getting and setting certain css properties. This means normalizing properties like background-position can easily be done via plugins.

They are similar in concept to the special event hooks. Return false from the hook to revert control back to jQuery's normal processes for getting and setting certain css properties.

src/css.js

@@ -35,22 +35,30 @@ jQuery.fn.css = function( name, value ) {
 };
 
 jQuery.extend({
-	style: function( elem, name, value ) {
-		// don't set styles on text and comment nodes
-		if ( !elem || elem.nodeType === 3 || elem.nodeType === 8 ) {
-			return undefined;
+	cssHooks: {
+		opacity: {
+			get: function( elem, force ) {
+				var style = elem.style;
+				if ( jQuery.support.opacity && !style.filter ) {
+					return false; // move along, nothing to see here
 				}
 
-		// ignore negative width and height values #1599
-		if ( (name === "width" || name === "height") && parseFloat(value) < 0 ) {
-			value = undefined;
-		}
+				// IE uses filters for opacity
+				var ret = ropacity.test(elem.currentStyle.filter || "") ?
+							(parseFloat(RegExp.$1) / 100) + "" :
+							"";
 
-		var style = elem.style || elem, set = value !== undefined;
+				return ret === "" ?
+					"1" :
+					ret;
+			},
+
+			set: function( elem, value ) {
+				var style = elem.style;
+				if ( jQuery.support.opacity && !style.filter ) {
+					return false; // move along, nothing to see here
+				}
 
-		// IE uses filters for opacity
-		if ( !jQuery.support.opacity && name === "opacity" && style.filter ) {
-			if ( set ) {
 				// IE has trouble with opacity if it does not have layout
 				// Force it by setting the zoom level
 				style.zoom = 1;
@@ -60,12 +68,22 @@ jQuery.extend({
 				var filter = style.filter || jQuery.curCSS( elem, "filter" ) || "";
 				style.filter = ralpha.test(filter) ? filter.replace(ralpha, opacity) : opacity;
 			}
+		}
+	},
 
-			return style.filter && style.filter.indexOf("opacity=") >= 0 ?
-				(parseFloat( ropacity.exec(style.filter)[1] ) / 100) + "":
-				"";
+	style: function( elem, name, value ) {
+		// don't set styles on text and comment nodes
+		if ( !elem || elem.nodeType === 3 || elem.nodeType === 8 ) {
+			return undefined;
 		}
 
+		// ignore negative width and height values #1599
+		if ( (name === "width" || name === "height") && parseFloat(value) < 0 ) {
+			value = undefined;
+		}
+
+		var style = elem.style || elem, set = value !== undefined;
+
 		// Make sure we're using the right name for getting the float value
 		if ( rfloat.test( name ) ) {
 			name = styleFloat;
@@ -73,9 +91,20 @@ jQuery.extend({
 
 		name = name.replace(rdashAlpha, fcamelCase);
 
+		var hooks = jQuery.cssHooks[name] || {};
+
 		if ( set ) {
+			if ( !('set' in hooks) || hooks.set( elem, value ) === false ) {
 				style[ name ] = value;
 			}
+		}
+
+		if ( 'get' in hooks ) {
+			var cssHookReturn = hooks.get( elem, false );
+			if ( cssHookReturn !== false ) {
+				return cssHookReturn;
+			}
+		}
 
 		return style[ name ];
 	},
@@ -98,24 +127,17 @@ jQuery.extend({
 	},
 
 	curCSS: function( elem, name, force ) {
-		var ret, style = elem.style, filter;
-
-		// IE uses filters for opacity
-		if ( !jQuery.support.opacity && name === "opacity" && elem.currentStyle ) {
-			ret = ropacity.test(elem.currentStyle.filter || "") ?
-				(parseFloat(RegExp.$1) / 100) + "" :
-				"";
-
-			return ret === "" ?
-				"1" :
-				ret;
-		}
+		var ret, style = elem.style, filter, hooks = jQuery.cssHooks[name] || {};
 
 		// Make sure we're using the right name for getting the float value
 		if ( rfloat.test( name ) ) {
 			name = styleFloat;
 		}
 
+		if ( 'get' in hooks && ( ret = hooks.get( elem, force ) ) !== false ) {
+			return ret;
+		}
+
 		if ( !force && style && style[ name ] ) {
 			ret = style[ name ];