Can I use this control as a search box in Windows Explorer in my own Qt / C ++ application? Or is it a custom control that I have to perform manually?
I have not seen such control, however in Qt it is easy to implement it manually. You can follow this guide: http://labs.qt.nokia.com/2007/06/06/lineedit-with-a-clear-button/ and just replace the icon with the search icon (and change the slot from clear()to what performs the desired search, of course).
clear()
Windows ; , , Explorer , , , , .