Press page up key in the paging box of a Listbox increases page number

Steps to Reproduce

1. http://www.zkoss.org/zkdemo/listbox/paging
2. click on paging box,
3. press page up

Actual Result

Page number increases to 2.

Expected Result

Page number should not change.

In common case, a user expects to switch to previous page when pressing page up and to switch to next page with page down. Therefore, pressing page down should increase the page number and page up should decrease the page number. Our current design has reversed meaning.

Besides, page up/down key should trigger page switching immediately without pressing enter.

Extra Information

Although a user can use page up/down key after he selects an item, but that switching also cause item selection change. If there is a onSelect listener in the server side, the selection change will cause unnecessary computing. Users might have such concern so that they try to avoid using page up/down after selecting an item.