Text input fields do not trigger input panel (on screen keyboard, handwriting panel)

On Windows 7, every text input field (such as the Explorer URL bar) shows a "keyboard input" tool tip to open the input panel on suitable hardware, such as Tablet PCs.

But this does not work with Qt widgets, because Qt does not tell the system which widgets accept text input.

The following link gives example code: http://msdn.microsoft.com/en-us/library/ms701162(v=VS.85).aspx