Understanding the Window WinMain Cycle

[BillBoeBaggins]

I am looking at the code in my WinMain, I know what it does,
I just don't know the exact particulars and what regulates it.

  while(TRUE)
        {
            if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
            {
                //Process the message
                if(msg.message==WM_QUIT) break;
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
            else
            {
                //Make sure the game engine isn't sleeping
                if(!GameEngine::GetEngine()->GetSleep())
                {
                    //Check the tick count to see if a game cycle has
elapsed
                    iTickCount=GetTickCount();
                    if(iTickCount>iTickTrigger)
                    {
                        iTickTrigger=iTickCount + 
                              GameEngine::GetEngine()->GetFrameDelay();
                        GameCycle();
                    }
                }
            }
        }

Question 1:
In the line if(PeekMessage(&msg,NULL,0,0,PM_REMOVE)) it
is passing the message to be Translated and Dispatched if it fails to Peek, but how would it know what the messag is if it could not peek at it?
So I am assuming that it is trying to peek, if it can then great perform a GameCycle, otherwise check to see it is a quit message, then translate it.
Question 2:
How often is this cycle of peeking messages ran through? Is it based on CPU Cycles...?


Just seeking to understand everything better...

Thanks for any responses.

[Ken Fitlike]

PeekMessage
messages and message queues.

>>it
is passing the message to be Translated and Dispatched if it fails to Peek<<

No.

msdn PeekMessage:
Return Value

If a message is available, the return value is nonzero.

If no messages are available, the return value is zero.

>>but how would it know what the messag is if it could not peek at it?<<

msdn PeekMessage:
checks the thread message queue for a posted message

>>So I am assuming that it is trying to peek, if it can then great perform a GameCycle, otherwise check to see it is a quit message, then translate it.<<

Other way around ie if there is a message, deal with it (including check for a quit message which should result in -er- quitting; that's what the break is for) else gamecycle.

[BillBoeBaggins]

Ok Ken, that makes sense. But how many times is GameCycle triggered per second per se. Is it based on computer speed...?

Thanks.

[novacain]

>>GameEngine::GetEngine()->GetFrameDelay();

This will return the number of millseconds between cycles.

PeekMessage() is called as fast as the PC can, using 100% of CPU time. If there is not a message it will return and the screen will be updated.
If the user is not doing anything there will not be a message and the GameEngine will be called.

So the frame rate is constant on all systems and for all types of user interation (ie the number of messages the user generates) the frame rate is regulated by the use of GetTickCount(). The app compares the current value to the value it got last time it updated the screen (last value+time between frames).

[BillBoeBaggins]

Thanks much for the help, I am going to look deeper into the code.