On-Screen keyboard: how is it done?

[Polaris]

Hi Experts:

I saw an PC without keyboard attached, it uses an on-screen keyboard
software program. When user clicks on a "key" (a button) on the program, the
program can find the currently active (focused) window application (for
example, notepad.exe) and input "typed" key into that active program; but
the keyboard program itself seems did not get activated while user click on
a button on it.

I could not figure out how it is accomplished? How does the keyboard program
avoid getting focus (active) even when user click on a "key" button of the
program? It must be able to do so in order to find the currently active
Windows program that user is working with (etc, a notepad.exe).

Thanks for your thoughts in advance.
Polaris

 

[Marcin Hoppe]

Polaris pisze:

Thanks for your thoughts in advance.

What I'd do if I were you and didn't want to buy an off-the-shelf
product (like itKeyboard from http://www.touch-soft.com/) would be to
download a trial version of an off-the-shelf product and use Spy++ to
look at messages that it sends and receives.

Best regards!

 

[Scott Seligman]

I could not figure out how it is accomplished? How does the keyboard program
avoid getting focus (active) even when user click on a "key" button of the
program? It must be able to do so in order to find the currently active
Windows program that user is working with (etc, a notepad.exe).

The window has the WS_EX_NOACTIVATE extended window style set.

 

[David Ching]

The window has the WS_EX_NOACTIVATE extended window style set.

Very cool... I had not known about this style. Before Win2K, the way to do
it was to intercept WM_MOUSEACTIVATE and return MA_NOACTIVATE (or
MA_NOACTIVATEANDEAT).

-- David

 

[clintonG]

Go look around http://www.codeproject.com/