Ticket 8099, Reattempt with iframe

src/effects.js

@@ -548,17 +548,42 @@ if ( jQuery.expr && jQuery.expr.filters ) {
 }
 
 function defaultDisplay( nodeName ) {
-	if ( !elemdisplay[ nodeName ] ) {
-		var elem = jQuery("<" + nodeName + ">").appendTo("body"),
-			display = elem.css("display");
+	var stylesheets = document.styleSheets,
+			disabled = [],
+			elem, display, style, idx;
 
+	if ( !elemdisplay[ nodeName ] ) {
+
+		// #8099 - If the end-dev has globally changed a default
+		// display, we can temporarily disable their styles to check
+		// for the correct default value
+		for ( idx = 0; idx < stylesheets.length; ++idx  ) {
+			style = stylesheets[ idx ];
+			disabled[ idx ] = style.disabled;
+			style.disabled = true;
+		}
+		
+		// To accurately check an element's default display value, 
+		// create a temp element and check it's default display, this
+		// will ensure that the value returned is not a user-tampered
+		// value.
+		elem = jQuery("<" + nodeName + ">").appendTo("body"),
+		display = elem.css("display");
+		
+		// Remove temp element
 		elem.remove();
 
 		if ( display === "none" || display === "" ) {
 			display = "block";
 		}
-
+		
+		// Store the correct default display
 		elemdisplay[ nodeName ] = display;
+
+		// Restore stylesheets
+		for ( idx = 0; idx < stylesheets.length; ++idx  ) {
+			stylesheets[ idx ].disabled = disabled[ idx ];
+		}
 	}
 
 	return elemdisplay[ nodeName ];

test/data/testsuite.css

@@ -109,3 +109,6 @@ div#show-tests * { display: none; }
 #nothiddendiv { font-size: 16px; }
 #nothiddendivchild.em { font-size: 2em; }
 #nothiddendivchild.prct { font-size: 150%; }
+
+/* 8099 changes to default styles are read correctly */
+tt { display: none; }

test/unit/effects.js

@@ -162,6 +162,19 @@ test("Persist correct display value", function() {
 	});
 });
 
+test("show() resolves correct default display #8099", function() {
+	expect(3);
+	var bug8099 = jQuery("<tt/>").appendTo("#main");
+
+	equals( bug8099.css("display"), "none", "default display override for all tt" );
+	equals( bug8099.show().css("display"), "inline", "Correctly resolves display:inline" );
+
+	bug8099.remove();
+
+	equals( jQuery("#foo").hide().show().css("display"), "block", "Correctly resolves display:block after hide/show" );
+});
+
+
 test("animate(Hash, Object, Function)", function() {
 	expect(1);
 	stop();