Thread Problem for GetWindowText API

When I try to use GetWindowText in one thread (t1) to get the text of window from the other thread (t2), I have some unknow problem. The call from t1 work normally when t2 window is idle, but the call from t1 is blocking when t2 window is looping for something. t1 is block until t2 window end looping.

What is this problem? Why t1 is block? How to solve it? This problem also occur when using SendMessage, why?

:confused: :confused: :confused:

Because in order to process SendMessage or GetWindowText which involves SendMessage, thread should get to it's message loop. If thread is busy by some other processing, you should wait. I guess you should use some additional thread in order to separate UI and processing