Take '$.ui.dialog.maxZ' and 'self.overlay' into account.

Author: PaulUithol

tests/unit/dialog/dialog_options.js

@@ -442,7 +442,7 @@ test("width", function() {
 });
 
 test("zIndex", function() {
-	expect(6);
+	expect(9);
 
 	el = $('<div></div>').dialog( { autoOpen: false } );
 		equals(dlg().css( 'zIndex' ), 1000, "default zIndex");
@@ -454,11 +454,16 @@ test("zIndex", function() {
 		equals(dlg().css( 'zIndex' ), $.ui.dialog.maxZ, "default zIndex");
 	el.remove();
 
-	// The z-index will always be 1 higher than requested if 'moveToTop' gets called, such as when 'autoOpen' is true.
-	el = $('<div></div>').dialog({zIndex: 2932 });
-		equals(dlg().css('zIndex'), 2932 + 1, "explicit zIndex");
+	// The z-index will be 1 higher than requested if 'moveToTop' gets called, such as when 'autoOpen' is true.
+	newZIndex = $.ui.dialog.maxZ + 2932;
+	el = $('<div></div>').dialog({zIndex: newZIndex });
+		equals(dlg().css('zIndex'), newZIndex + 1, "explicit zIndex");
+		equals( el.dialog( 'option', 'zIndex' ), newZIndex, 'get works for zIndex' );
+		equals( newZIndex + 1, $.ui.dialog.maxZ, '$.ui.dialog.maxZ is updated to the new value' );
+		
 		el.dialog('option', 'zIndex', 1748);
 		equals(dlg().css('zIndex'), 1748, 'explicit zIndex after init');
+		equals( el.dialog( 'option', 'zIndex' ), 1748 );
 	el.remove();
 
 	// At the moment, an explicit zIndex option lower than $.ui.dialog.maxZ will be ignored since 'open' calls

ui/jquery.ui.dialog.js

@@ -596,7 +596,20 @@ $.widget("ui.dialog", {
 					.html( "" + ( value || " " ) );
 				break;
 			case "zIndex":
-				uiDialog.css({ zIndex: value });
+				if ( value > $.ui.dialog.maxZ ) {
+					$.ui.dialog.maxZ = value;
+					
+					if ( self.overlay ) {
+						$.ui.dialog.maxZ += 1;
+						$.ui.dialog.overlay.maxZ = $.ui.dialog.maxZ;
+					}
+					
+					value = $.ui.dialog.maxZ;
+				}
+				
+				self.overlay && self.overlay.$el.css( "z-index", value > 0 ? value : 0 );
+				uiDialog.css( "z-index", value );
+				
 				break;
 		}