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

2 files changed, 64 insertions, 59 deletions

diff --git a/src/css.js b/src/css.js
index 2616572a7..d8aa6d605 100644
--- a/src/css.js
+++ b/src/css.js
@@ -164,7 +164,7 @@ 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,
diff --git a/src/effects.js b/src/effects.js
index 6f8685699..bb10b73f8 100644
--- a/src/effects.js
+++ b/src/effects.js
@@ -5,44 +5,51 @@ 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" );
-
-				// 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;
-
-					do {
-						// If previous iteration zeroed out, double until we get *something*
-						// Use a string for doubling factor so we don't accidentally see scale as unchanged below
-						scale = scale || ".5";
-
-						// Adjust and apply
-						start = start / scale;
-						jQuery.style( tween.elem, prop, start + unit );
-
-					// Update scale, tolerating zero or NaN from tween.cur()
-					// And breaking the loop if scale is unchanged or perfect, or if we've just had enough
-					} while ( scale !== (scale = tween.cur() / target) && scale !== 1 && --maxIterations );
-				}
+			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 || [];
 
+				// Iteratively approximate from a nonzero starting point
+				start = +target || 1;
+
+				do {
+					// If previous iteration zeroed out, double until we get *something*
+					// Use a string for doubling factor so we don't accidentally see scale as unchanged below
+					scale = scale || ".5";
+
+					// Adjust and apply
+					start = start / scale;
+					jQuery.style( tween.elem, prop, start + unit );
+
+				// Update scale, tolerating zero or NaN from tween.cur()
+				// And breaking the loop if scale is unchanged or perfect, or if we've just had enough
+				} 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[ "*" ] ),
-			index = 0,
-			length = collection.length;
-		for ( ; index < length; index++ ) {
-			if ( collection[ index ].call( animation, prop, value ) ) {
+function createTween( value, prop, animation ) {
+	var tween,
+		collection = ( tweeners[ prop ] || [] ).concat( tweeners[ "*" ] ),
+		index = 0,
+		length = collection.length;
+	for ( ; index < length; index++ ) {
+		if ( (tween = collection[ index ].call( animation, prop, value )) ) {
 
-				// we're done with this property
-				return;
-			}
+			// we're done with this property
+			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 );
@@ -243,12 +249,12 @@ jQuery.Animation = jQuery.extend( Animation, {
 
 function defaultPrefilter( elem, props, opts ) {
 	/* jshint validthis: true */
-	var index, prop, value, length, dataShow, toggle, tween, hooks, oldfire,
+	var index, 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 = data_priv.get( elem, "fxshow" );
 
 	// handle queue: false promises
 	if ( !opts.queue ) {
@@ -304,7 +310,6 @@ function defaultPrefilter( elem, props, opts ) {
 
 
 	// show/hide pass
-	dataShow = data_priv.get( elem, "fxshow" );
 	for ( index in props ) {
 		value = props[ index ];
 		if ( rfxtypes.exec( value ) ) {
@@ -313,21 +318,23 @@ function defaultPrefilter( elem, props, opts ) {
 			if ( value === ( hidden ? "hide" : "show" ) ) {
 
 				// If there is dataShow left over from a stopped hide or show and we are going to proceed with show, we should pretend to be hidden
-				if( value === "show" && dataShow !== undefined && dataShow[ index ] !== undefined ) {
+				if ( value === "show" && dataShow && dataShow[ index ] !== undefined ) {
 					hidden = true;
 				} else {
 					continue;
 				}
 			}
-			handled.push( index );
+			orig[ index ] = dataShow && dataShow[ index ] || jQuery.style( elem, index );
 		}
 	}
 
-	length = handled.length;
-	if ( length ) {
-		dataShow = data_priv.get( elem, "fxshow" ) || data_priv.access( elem, "fxshow", {} );
-		if ( "hidden" in dataShow ) {
-			hidden = dataShow.hidden;
+	if ( !jQuery.isEmptyObject( orig ) ) {
+		if ( dataShow ) {
+			if ( "hidden" in dataShow ) {
+				hidden = dataShow.hidden;
+			}
+		} else {
+			dataShow = data_priv.access( elem, "fxshow", {} );
 		}
 
 		// store state if its toggle - enables .stop().toggle() to "reverse"
@@ -349,10 +356,8 @@ 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;