Steps to Reproduce

1. visit http://www.zkoss.org/zkdemo/layout/splitter

       <panel title="Splitter" border="normal" width="500px" >
           <panelchildren>
               <hbox spacing="0" width="100%" height="100%">
                   <vbox spacing="0" width="100%"  heights="130px,130px">
                       Column 1-1: The left-top box. To know whether a splitter
                       is collapsed, you can listen to the onOpen event.
                       <splitter id="s1" collapse="before"/>
                       Column 1-2: You can enforce to open or collapse programming
                       by calling setOpen method.
                   </vbox>
                   <splitter id="s2" collapse="before"/>
                   Column 2: Whether a splitter allows users to open or collapse
                   depending on the collapse attribute.
               </hbox>
           </panelchildren>
       </panel>
   

2. follow steps in attached video

Actual Result

There are main 2 issues

1. when move up horizontal splitter, vertical splitter also change its position.
2. when move up horizontal splitter and reduce the upper area smaller than its content, the panel's height will increase.

Expected Result

1. vertical splitter should keep its position
2. panel's height doesn't change.