CSS: Ignore the CSS cascade in show()/hide()/etc.

Fixes gh-1767
Fixes gh-2071
Closes gh-2180

(cherry picked from commit 86419b10bfa5e3b71a7d416288ab806d47a31d1f)

Conflicts:
	src/css.js
	src/css/defaultDisplay.js
	src/effects.js
	test/data/testsuite.css
	test/unit/css.js
	test/unit/effects.js

1 files changed, 45 insertions, 0 deletions

diff --git a/src/css/showHide.js b/src/css/showHide.js
new file mode 100644
index 000000000..f500f186f
--- /dev/null
+++ b/src/css/showHide.js
@@ -0,0 +1,45 @@
+define([], function() {
+
+function showHide( elements, show ) {
+	var display, elem,
+		values = [],
+		index = 0,
+		length = elements.length;
+
+	// Determine new display value for elements that need to change
+	for ( ; index < length; index++ ) {
+		elem = elements[ index ];
+		if ( !elem.style ) {
+			continue;
+		}
+
+		display = elem.style.display;
+		if ( show ) {
+			if ( display === "none" ) {
+				// Restore a pre-hide() value if we have one
+				values[ index ] = jQuery._data( elem, "display" ) || "";
+			}
+		} else {
+			if ( display !== "none" ) {
+				values[ index ] = "none";
+
+				// Remember the value we're replacing
+				jQuery._data( elem, "display", display );
+			}
+		}
+	}
+
+	// Set the display of the elements in a second loop
+	// to avoid the constant reflow
+	for ( index = 0; index < length; index++ ) {
+		if ( values[ index ] != null ) {
+			elements[ index ].style.display = values[ index ];
+		}
+	}
+
+	return elements;
+}
+
+return showHide;
+
+});