100%cpu usage with PeekMessage

I've just noticed something, if I use this piece of code for processing messages, I get 100% CPU usage when the window is in the background:

Code:

done = false;						
while (!done) {
    PeekMessage(&msg, hwnd, NULL, NULL, PM_REMOVE);
    if (msg.message == WM_QUIT) {
        done = true;
    } else {
        TranslateMessage(&msg);
	DispatchMessage(&msg);
    }
}

while, this doesn't cause 100% CPU usage:

Code:

while (GetMessage(&msg, NULL, 0, 0)) {
	TranslateMessage(&msg);
	DispatchMessage(&msg);
}

Any idea why?

GetMessage is blocking. PeekMessage( ) isn't.

then I wonder why NeHe uses PeekMessage instead of GetMessage, his basecode cause 100% CPU usage when inactive, is there a reason for using PeekMessage or I should email him suggesting to change it to GetMessage?

GetMessage() will not return until there is a msg. Therefore no processing outside the main loop is possible.

PeekMessage() just asks for a msg and returns (even if there is no msg). This allows other processing to be done while the app would normally be idle (waiting for the GetMessage() to return with a msg).

Use Peek only for games ect not normal apps.





EDIT Spelling:: Pity there is not a WIN32 function 'GetMassage()'

If you need to use PeekMessage, place a WaitMessage prior to the PeekMessage call.

Originally posted by novacain
GetMessage() will not return until there is a msg. Therefore no processing outside the main loop is possible.

PeekMessage() just asks for a msg and returns (even if there is no msg). This allows other processing to be done while the app would normally be idle (waiting for the GetMessage() to return with a msg).

Use Peek only for games ect not normal apps.





EDIT Spelling:: Pity there is not a WIN32 function 'GetMassage()'

I figured this out later, thx, so this the reason why NeHe uses PeekMessage, otherwise, if there are no messages, the screen won't be updated.

a microsoft API called GetMassage? who would do it? Gates? ewwww.....