Steps to Reproduce

http://zkfiddle.org/sample/2b6ubc4/1-Combowidget-dropdown-keypress
run fiddle
Focus into the combobox
input "Ctrl+tab" to navigate to the textbox located before the combobox

Current Result

Ctrl keypress triggers the combobox autodrop

Expected Result

Ctrl keypress shouldn't triggers the combobox autodrop

Debug Info

Other non content relevant keypresses also trigger autodrop (alt, numlock, context menu key, volume keys if any, insert key, pause key, etc.)
Exceptions: these keys do not trigger popup: escape, print screen.

Pasting content in the input without using keyboard (ex: right click, paste) doesn't open the popup, even though this action modify the value of the combowidget.

Root Cause

Current implementation uses onKeyPress listeners, with a set of actions depending on the key value
Possible improvement could be to use an onInput or onChange listener to listen to changes on the input element, while still listening the specific onKeyPress for utility keys (up down escape, etc)

Workaround