Dimensions: Detect and account for content-box dimension mishandling

Fixes gh-3699
Closes gh-3700

src/css.js

@@ -148,10 +148,10 @@ function boxModelAdjustment( elem, dimension, box, isBorderBox, styles, computed
 function getWidthOrHeight( elem, dimension, extra ) {
 
 	// Start with computed style
-	var valueIsBorderBox,
-		styles = getStyles( elem ),
+	var styles = getStyles( elem ),
 		val = curCSS( elem, dimension, styles ),
-		isBorderBox = jQuery.css( elem, "boxSizing", false, styles ) === "border-box";
+		isBorderBox = jQuery.css( elem, "boxSizing", false, styles ) === "border-box",
+		valueIsBorderBox = isBorderBox;
 
 	// Computed unit is not pixels. Stop here and return.
 	if ( rnumnonpx.test( val ) ) {
@@ -160,7 +160,7 @@ function getWidthOrHeight( elem, dimension, extra ) {
 
 	// Check for style in case a browser which returns unreliable values
 	// for getComputedStyle silently falls back to the reliable elem.style
-	valueIsBorderBox = isBorderBox &&
+	valueIsBorderBox = valueIsBorderBox &&
 		( support.boxSizingReliable() || val === elem.style[ dimension ] );
 
 	// Fall back to offsetWidth/Height when value is "auto"
@@ -367,14 +367,26 @@ jQuery.each( [ "height", "width" ], function( i, dimension ) {
 		set: function( elem, value, extra ) {
 			var matches,
 				styles = getStyles( elem ),
+				isBorderBox = jQuery.css( elem, "boxSizing", false, styles ) === "border-box",
 				subtract = extra && boxModelAdjustment(
 					elem,
 					dimension,
 					extra,
-					jQuery.css( elem, "boxSizing", false, styles ) === "border-box",
+					isBorderBox,
 					styles
 				);
 
+			// Account for unreliable border-box dimensions by comparing offset* to computed and
+			// faking a content-box to get border and padding (gh-3699)
+			if ( isBorderBox && !support.borderBoxReliable() ) {
+				subtract -= Math.ceil(
+					elem[ "offset" + dimension[ 0 ].toUpperCase() + dimension.slice( 1 ) ] -
+					parseFloat( styles[ dimension ] ) -
+					boxModelAdjustment( elem, dimension, "border", false, styles ) -
+					0.5
+				);
+			}
+
 			// Convert to pixels if value adjustment is needed
 			if ( subtract && ( matches = rcssNum.exec( value ) ) &&
 				( matches[ 3 ] || "px" ) !== "px" ) {

src/css/support.js

@@ -31,12 +31,16 @@ define( [
 
 		// Support: Android 4.0 - 4.3 only, Firefox <=3 - 44
 		reliableMarginLeftVal = divStyle.marginLeft === "2px";
-		boxSizingReliableVal = divStyle.width === "4px";
+		boxSizingReliableVal = divStyle.width === "5px";
+
+		// Support: IE 9 only
+		// Detect misreporting of content dimensions for border-box elements (gh-3699)
+		borderBoxReliableVal = divStyle.width[ 0 ] === "5";
 
 		// Support: Android 4.0 - 4.3 only
 		// Some styles come back with percentage values, even though they shouldn't
 		div.style.marginRight = "50%";
-		pixelMarginRightVal = divStyle.marginRight === "4px";
+		pixelMarginRightVal = divStyle.marginRight === "5px";
 
 		documentElement.removeChild( container );
 
@@ -45,7 +49,8 @@ define( [
 		div = null;
 	}
 
-	var pixelPositionVal, boxSizingReliableVal, pixelMarginRightVal, reliableMarginLeftVal,
+	var pixelPositionVal, boxSizingReliableVal, borderBoxReliableVal, pixelMarginRightVal,
+		reliableMarginLeftVal,
 		container = document.createElement( "div" ),
 		div = document.createElement( "div" );
 
@@ -60,19 +65,23 @@ define( [
 	div.cloneNode( true ).style.backgroundClip = "";
 	support.clearCloneStyle = div.style.backgroundClip === "content-box";
 
-	container.style.cssText = "border:0;width:8px;height:0;top:0;left:-9999px;" +
+	container.style.cssText = "border:0;width:10px;height:0;top:0;left:-9999px;" +
 		"padding:0;margin-top:1px;position:absolute";
 	container.appendChild( div );
 
 	jQuery.extend( support, {
-		pixelPosition: function() {
+		borderBoxReliable: function() {
 			computeStyleTests();
-			return pixelPositionVal;
+			return borderBoxReliableVal;
 		},
 		boxSizingReliable: function() {
 			computeStyleTests();
 			return boxSizingReliableVal;
 		},
+		pixelPosition: function() {
+			computeStyleTests();
+			return pixelPositionVal;
+		},
 		pixelMarginRight: function() {
 			computeStyleTests();
 			return pixelMarginRightVal;

test/unit/dimensions.js

@@ -585,7 +585,14 @@ QUnit.test( "interaction with scrollbars (gh-3589)", function( assert ) {
 			.css( borderBox )
 			.css( { "box-sizing": "border-box" } )
 			.appendTo( parent ),
-		$boxes = jQuery( [ plainContentBox[ 0 ], contentBox[ 0 ], borderBox[ 0 ] ] );
+		$boxes = jQuery( [ plainContentBox[ 0 ], contentBox[ 0 ], borderBox[ 0 ] ] ),
+
+		// Support: IE 9 only
+		// Computed width seems to report content width even with "box-sizing: border-box", and
+		// "overflow: scroll" actually _shrinks_ the element (gh-3699).
+		borderBoxLoss =
+			borderBox.clone().css( { overflow: "auto" } ).appendTo( parent )[ 0 ].offsetWidth -
+			borderBox[ 0 ].offsetWidth;
 
 	for ( i = 0; i < 3; i++ ) {
 		if ( i === 1 ) {
@@ -616,13 +623,13 @@ QUnit.test( "interaction with scrollbars (gh-3589)", function( assert ) {
 		assert.equal( contentBox.outerHeight(), size + 2 * padding + 2 * borderWidth,
 			"content-box outerHeight includes scroll gutter" + suffix );
 
-		assert.equal( borderBox.innerWidth(), size - 2 * borderWidth,
+		assert.equal( borderBox.innerWidth(), size - borderBoxLoss - 2 * borderWidth,
 			"border-box innerWidth includes scroll gutter" + suffix );
-		assert.equal( borderBox.innerHeight(), size - 2 * borderWidth,
+		assert.equal( borderBox.innerHeight(), size - borderBoxLoss - 2 * borderWidth,
 			"border-box innerHeight includes scroll gutter" + suffix );
-		assert.equal( borderBox.outerWidth(), size,
+		assert.equal( borderBox.outerWidth(), size - borderBoxLoss,
 			"border-box outerWidth includes scroll gutter" + suffix );
-		assert.equal( borderBox.outerHeight(), size,
+		assert.equal( borderBox.outerHeight(), size - borderBoxLoss,
 			"border-box outerHeight includes scroll gutter" + suffix );
 	}
 } );