Fix #13855: line-height animations. Close gh-1265.

(cherry picked from commit 3971c2eb)

src/css.js

@@ -161,7 +161,7 @@ jQuery.extend({
 		}
 	},
 
-	// Exclude the following css properties to add px
+	// Don't automatically add "px" to these possibly-unitless properties
 	cssNumber: {
 		"columnCount": true,
 		"fillOpacity": true,

src/effects.js

@@ -5,24 +5,26 @@ var fxNow, timerId,
 	animationPrefilters = [ defaultPrefilter ],
 	tweeners = {
 		"*": [function( prop, value ) {
-			var end, unit,
-				tween = this.createTween( prop, value ),
-				parts = rfxnum.exec( value ),
+			var tween = this.createTween( prop, value ),
 				target = tween.cur(),
-				start = +target || 0,
+				parts = rfxnum.exec( value ),
+				unit = parts && parts[ 3 ] || ( jQuery.cssNumber[ prop ] ? "" : "px" ),
+
+				// Starting value computation is required for potential unit mismatches
+				start = ( jQuery.cssNumber[ prop ] || unit !== "px" && +target ) &&
+					rfxnum.exec( jQuery.css( tween.elem, prop ) ),
 				scale = 1,
 				maxIterations = 20;
 
-			if ( parts ) {
-				end = +parts[2];
-				unit = parts[3] || ( jQuery.cssNumber[ prop ] ? "" : "px" );
+			if ( start && start[ 3 ] !== unit ) {
+				// Trust units reported by jQuery.css
+				unit = unit || start[ 3 ];
+
+				// Make sure we update the tween properties later on
+				parts = parts || [];
 
-				// We need to compute starting value
-				if ( unit !== "px" && start ) {
 				// Iteratively approximate from a nonzero starting point
-					// Prefer the current property, because this process will be trivial if it uses the same units
-					// Fallback to end or a simple constant
-					start = jQuery.css( tween.elem, prop, true ) || end || 1;
+				start = +target || 1;
 
 				do {
 					// If previous iteration zeroed out, double until we get *something*
@@ -38,11 +40,16 @@ var fxNow, timerId,
 				} while ( scale !== (scale = tween.cur() / target) && scale !== 1 && --maxIterations );
 			}
 
+			// Update tween properties
+			if ( parts ) {
 				tween.unit = unit;
-				tween.start = start;
+				tween.start = +start || +target || 0;
 				// If a +=/-= token was provided, we're doing a relative animation
-				tween.end = parts[1] ? start + ( parts[1] + 1 ) * end : end;
+				tween.end = parts[ 1 ] ?
+					start + ( parts[ 1 ] + 1 ) * parts[ 2 ] :
+					+parts[ 2 ];
 			}
+
 			return tween;
 		}]
 	};
@@ -55,19 +62,18 @@ function createFxNow() {
 	return ( fxNow = jQuery.now() );
 }
 
-function createTweens( animation, props ) {
-	jQuery.each( props, function( prop, value ) {
-		var collection = ( tweeners[ prop ] || [] ).concat( tweeners[ "*" ] ),
+function createTween( value, prop, animation ) {
+	var tween,
+		collection = ( tweeners[ prop ] || [] ).concat( tweeners[ "*" ] ),
 		index = 0,
 		length = collection.length;
 	for ( ; index < length; index++ ) {
-			if ( collection[ index ].call( animation, prop, value ) ) {
+		if ( (tween = collection[ index ].call( animation, prop, value )) ) {
 
 			// we're done with this property
-				return;
+			return tween;
 		}
 	}
-	});
 }
 
 function Animation( elem, properties, options ) {
@@ -153,7 +159,7 @@ function Animation( elem, properties, options ) {
 		}
 	}
 
-	createTweens( animation, props );
+	jQuery.map( props, createTween, animation );
 
 	if ( jQuery.isFunction( animation.opts.start ) ) {
 		animation.opts.start.call( elem, animation );
@@ -243,14 +249,12 @@ jQuery.Animation = jQuery.extend( Animation, {
 
 function defaultPrefilter( elem, props, opts ) {
 	/* jshint validthis: true */
-	var prop, index, length,
-		value, dataShow, toggle,
-		tween, hooks, oldfire,
+	var prop, value, toggle, tween, hooks, oldfire,
 		anim = this,
-		style = elem.style,
 		orig = {},
-		handled = [],
-		hidden = elem.nodeType && isHidden( elem );
+		style = elem.style,
+		hidden = elem.nodeType && isHidden( elem ),
+		dataShow = jQuery._data( elem, "fxshow" );
 
 	// handle queue: false promises
 	if ( !opts.queue ) {
@@ -315,24 +319,26 @@ function defaultPrefilter( elem, props, opts ) {
 
 
 	// show/hide pass
-	for ( index in props ) {
-		value = props[ index ];
+	for ( prop in props ) {
+		value = props[ prop ];
 		if ( rfxtypes.exec( value ) ) {
-			delete props[ index ];
+			delete props[ prop ];
 			toggle = toggle || value === "toggle";
 			if ( value === ( hidden ? "hide" : "show" ) ) {
 				continue;
 			}
-			handled.push( index );
+			orig[ prop ] = dataShow && dataShow[ prop ] || jQuery.style( elem, prop );
 		}
 	}
 
-	length = handled.length;
-	if ( length ) {
-		dataShow = jQuery._data( elem, "fxshow" ) || jQuery._data( elem, "fxshow", {} );
+	if ( !jQuery.isEmptyObject( orig ) ) {
+		if ( dataShow ) {
 			if ( "hidden" in dataShow ) {
 				hidden = dataShow.hidden;
 			}
+		} else {
+			dataShow = jQuery._data( elem, "fxshow", {} );
+		}
 
 		// store state if its toggle - enables .stop().toggle() to "reverse"
 		if ( toggle ) {
@@ -352,10 +358,8 @@ function defaultPrefilter( elem, props, opts ) {
 				jQuery.style( elem, prop, orig[ prop ] );
 			}
 		});
-		for ( index = 0 ; index < length ; index++ ) {
-			prop = handled[ index ];
-			tween = anim.createTween( prop, hidden ? dataShow[ prop ] : 0 );
-			orig[ prop ] = dataShow[ prop ] || jQuery.style( elem, prop );
+		for ( prop in orig ) {
+			tween = createTween( hidden ? dataShow[ prop ] : 0, prop, anim );
 
 			if ( !( prop in dataShow ) ) {
 				dataShow[ prop ] = tween.start;

test/unit/effects.js

@@ -1405,6 +1405,44 @@ test("Do not append px to 'fill-opacity' #9548", 1, function() {
 	});
 });
 
+test("line-height animates correctly (#13855)", function() {
+	expect( 12 );
+	stop();
+
+	var
+		animated = jQuery(
+			"<p style='line-height: 4;'>unitless</p>" +
+			"<p style='line-height: 50px;'>px</p>" +
+			"<p style='line-height: 420%;'>percent</p>" +
+			"<p style='line-height: 2.5em;'>em</p>"
+		).appendTo("#qunit-fixture"),
+		initialHeight = jQuery.map( animated, function( el ) {
+			return jQuery( el ).height();
+		});
+
+	animated.animate( { "line-height": "hide" }, 1500 );
+	setTimeout(function() {
+		animated.each(function( i ) {
+			var label = jQuery.text( this ),
+				initial = initialHeight[ i ],
+				height = jQuery( this ).height();
+			ok( height < initial, "hide " + label + ": upper bound" );
+			ok( height > initial / 2, "hide " + label + ": lower bound" );
+		});
+		animated.stop( true, true ).hide().animate( { "line-height": "show" }, 1500 );
+		setTimeout(function() {
+			animated.each(function( i ) {
+				var label = jQuery.text( this ),
+					initial = initialHeight[ i ],
+					height = jQuery( this ).height();
+				ok( height < initial / 2, "show " + label + ": upper bound" );
+			});
+			animated.stop( true, true );
+			start();
+		}, 400 );
+	}, 400 );
+});
+
 // Start 1.8 Animation tests
 asyncTest( "jQuery.Animation( object, props, opts )", 4, function() {
 	var animation,