What is the difference between the
PostMessage - Queues the message, and the code runs further.
SendMessage - The SendMessage function sends a message immediately.
(Refinement-commentary on the answer @Asen )
SendMessage, if you use your terminology, “send a message right away,” because the only thing you can send messages to (with the exception of Nonqueued messages ) is in some internal queue .
This is implemented as otherwise the solution of
race conditionslike "50 threads simultaneously sent
SendMessage" would be very problematic.
The most important thing to write about these functions is that
SendMessagewaits for the message to be processed and returns the result, while
PostMessagesimply puts the message into a queue and does not care what happens next.
The latter fact, by the way, is noticeable from their signatures:
BOOL WINAPI PostMessage(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam); LRESULT WINAPI SendMessage(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
SendMessage is synchronous, PostMessage is asynchronous.