Fix ticket 10503

Rewrote some unclear code, this might not be performant

src/effects.js

@@ -25,39 +25,19 @@ jQuery.fn.extend({
 		} else {
 			for ( var i = 0, j = this.length; i < j; i++ ) {
 				elem = this[i];
-
-				if ( elem.style ) {
-					display = elem.style.display;
-
-					// Reset the inline display of this element to learn if it is
-					// being hidden by cascaded rules or not
-					if ( !jQuery._data(elem, "olddisplay") && display === "none" ) {
-						display = elem.style.display = "";
-					}
-
-					// Set elements which have been overridden with display: none
-					// in a stylesheet to whatever the default browser style is
-					// for such an element
-					if ( display === "none" || ( display === ""  && jQuery.css( elem, "display" ) === "none" ) ) {
-						jQuery._data(elem, "olddisplay", defaultDisplay(elem.nodeName));
-					}
-				}
-			}
-
-			// Set the display of most of the elements in a second loop
-			// to avoid the constant reflow
-			for ( i = 0; i < j; i++ ) {
-				elem = this[i];
-
-				if ( elem.style ) {
-					display = elem.style.display;
-
-					if ( display === "" || display === "none" ) {
-						elem.style.display = jQuery._data(elem, "olddisplay") || "";
+				var cachedDisplay = jQuery._data(elem, "olddisplay"),
+					defaultsForElems = {};
+				if ( elem.style) {
+					if ( cachedDisplay ) {
+						elem.style.display = cachedDisplay;
+					} else {
+						if ( !defaultsForElems[elem.nodeName] ) {
+							defaultsForElems[elem.nodeName] = defaultDisplay(elem.nodeName);
+						}
+						elem.style.display = defaultsForElems[elem.nodeName];
 					}
 				}
 			}
-
 			return this;
 		}
 	},

test/unit/effects.js

@@ -6,7 +6,7 @@ test("sanity check", function() {
 });
 
 test("show()", function() {
-	expect(28);
+	expect(29);
 
 	var hiddendiv = jQuery("div.hidden");
 
@@ -93,6 +93,11 @@ test("show()", function() {
 	// Make sure that showing or hiding a text node doesn't cause an error
 	jQuery("<div>test</div> text <span>test</span>").show().remove();
 	jQuery("<div>test</div> text <span>test</span>").hide().remove();
+
+	// Make sure elements maintain their correct display type after hiding/showing
+	var span = jQuery("<span style='display:block;'>test</span>").hide().show();
+	equals( "block", span.css("display") );
+	span.remove();
 });
 
 test("show(Number) - other displays", function() {