[Lazarus] Screen recording issues

[Krzysztof]

Hi,

There is article how to take a screen shot:
http://wiki.lazarus.freepascal.org/Developing_with_Graphics#Taking_a_screenshot_of_the_screen

But how record what happening on the screen? How those applications
work? They just take 25 screenshots per second like in above example?
I have not done any testing yet, but how efficient this could be?
Maybe exists any OS api for screen streaming?
My second question: how can I get only part of screen shot? I know how
to crop image after taking screenshot but can I do this before taking
screenshot?

Multiplatform solutions are appreciated ;)

Regards.