background

Users wants a floating scrollbar style like facebook, so they need a customizable, non-native scrollbar.

steps to reproduce

1. run http://zkfiddle.org/sample/1vrjjhd/2-borderlayout-scrollbar

   <borderlayout vflex="1" class="mainCenterArea">
     <custom-attributes org.zkoss.zul.nativebar="false"/>
   	<west size="350px" border="0" class="menuGroupboxContainer" autoscroll="true">
   		<vbox id="menuContainer" hflex="1"  spacing="0">
   			<groupbox class="menuGroupbox" open="false" hflex="1">
   				<caption label="Layer1 A" />
   				<vbox>
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   					<label value="Layer2 A" />
   				</vbox>
   			</groupbox>
   			<groupbox class="menuGroupbox" open="false" hflex="1">
   				<caption label="Layer1 B" />
   				<vbox>
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   					<label value="Layer2 B" />
   				</vbox>
   			</groupbox>
   		</vbox>
   	</west>
   </borderlayout>
   

2. shrink height less than 500px
3. open 2 groupboxes

result

no vertical scrollbar

expected result

vertical scrollbar appears.

h2 .debug info

• it doesn't happen when <custom-attributes org.zkoss.zul.nativebar="true"/>