help reading example file opengl.asm

[supercoollee]

DoEvents      PROC
         LOCAL   msg:MSG
StartLoop:
         invoke   PeekMessage,ADDR msg,0,0,0,PM_NOREMOVE
         or   eax,eax
         jz   NoMsg
         invoke   GetMessage,ADDR msg,NULL,0,0
         or   eax,eax
         jz   ExitLoop
         invoke   TranslateMessage,ADDR msg
         invoke   DispatchMessage,ADDR msg
         jmp   StartLoop
NoMsg:
         invoke   DrawScene
         jmp   StartLoop
ExitLoop:      mov   eax,msg.wParam
         ret
DoEvents      ENDP
========================================
in here, what is the meaning of "msg.wParam" ?

another thing, why in "Procedures Declarations" there is no "DoEvents PROTO ... "?
when should a PROC have the PROTO line ?

[clive]

wParam is a "word" parameter within the MSG structure. In Win32 it is a DWORD value, it was a WORD in Win16. In this case it contains a return value for the message loop when you quit.

You only need PROTO when the procedure is external to the ASM file you are using, or you use INVOKE before defining the body of the procedure (PROC/ENDP).

[supercoollee]

thanks.
so MSG is a predefined structure, if i don't know about this structure, i can't write the program by my own, is that right?
where can i learn about these basic predefined structures?

[qWord]

where can i learn about these basic predefined structures?

Iczelion's Tutorials

[joemc]

google "msg structure"

you can even click "I'm Feeling Lucky"

[GregL]

Search for them in MSDN.