Fixes #7912. Make sure .cur() only returns 0 as fallback value when it needs to ("", auto, undefined, null).

This change makes .cur() more .cssHooks friendly. .cur() now returns the unmodified value by
.css() if it isn't a number, number-alike or a value that needs a fallback to 0.
This way fx.start doesn't need to be recalculated for complex values.

2 files changed, 45 insertions, 18 deletions

diff --git a/src/effects.js b/src/effects.js
index fd832ce4a..d9e9a8b31 100644
--- a/src/effects.js
+++ b/src/effects.js
@@ -185,7 +185,7 @@ jQuery.fn.extend({
 
 				} else {
 					var parts = rfxnum.exec(val),
-						start = e.cur() || 0;
+						start = e.cur();
 
 					if ( parts ) {
 						var end = parseFloat( parts[2] ),
@@ -336,8 +336,12 @@ jQuery.fx.prototype = {
 			return this.elem[ this.prop ];
 		}
 
-		var r = parseFloat( jQuery.css( this.elem, this.prop ) );
-		return r || 0;
+		var parsed,
+			r = jQuery.css( this.elem, this.prop );
+		// Empty strings, null, undefined and "auto" are converted to 0,
+		// complex values such as "rotate(1rad)" are returned as is,
+		// simple values such as "10px" are parsed to Float.
+		return isNaN( parsed = parseFloat( r ) ) ? !r || r === "auto" ? 0 : r : parsed;
 	},
 
 	// Start an animation from one number to another
diff --git a/test/unit/effects.js b/test/unit/effects.js
index a07c076d7..4bb92fc00 100644
--- a/test/unit/effects.js
+++ b/test/unit/effects.js
@@ -558,21 +558,44 @@ jQuery.checkOverflowDisplay = function(){
 	start();
 }
 
-test("support negative values < -10000 (bug #7193)", function () {
-	expect(1);
-	stop();
-
-	jQuery.extend(jQuery.fx.step, {
-		"marginBottom": function(fx) {
-			equals( fx.cur(), -11000, "Element has margin-bottom of -11000" );
-			delete jQuery.fx.step.marginBottom;
-		}
-	});
-
-	jQuery("#main").css("marginBottom", "-11000px").animate({ marginBottom: "-11001px" }, {
-		duration: 1,
-		complete: start
-	});
+test("jQuery.fx.prototype.cur()", function() {
+	expect(5);
+	var nothiddendiv = jQuery('#nothiddendiv').css({
+			color: '#ABC',
+			border: '5px solid black',
+			left: 'auto',
+			marginBottom: '11000px'
+		})[0];
+
+	equals(
+		(new jQuery.fx( nothiddendiv, {}, 'color' )).cur(),
+		jQuery.css( nothiddendiv,'color' ),
+		"Return the same value as jQuery.css for complex properties (bug #7912)"
+	);
+
+	strictEqual(
+		(new jQuery.fx( nothiddendiv, {}, 'borderLeftWidth' )).cur(),
+		5,
+		"Return simple values parsed as Float"
+	);
+
+	strictEqual(
+		(new jQuery.fx( nothiddendiv, {}, 'backgroundPosition' )).cur(),
+		0,
+		'Return 0 when jQuery.css returns an empty string'
+	);
+
+	strictEqual(
+		(new jQuery.fx( nothiddendiv, {}, 'left' )).cur(),
+		0,
+		'Return 0 when jQuery.css returns "auto"'
+	);
+
+	equals(
+		(new jQuery.fx( nothiddendiv, {}, 'marginBottom' )).cur(),
+		11000,
+		"support negative values < -10000 (bug #7193)"
+	);
 });
 
 test("JS Overflow and Display", function() {