Event Handler

Tight_Coder_Ex Tight_Coder_Ex is offline Offline Feb 10th, 2005, 1:29 pm |
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I prefer to use this method as it doesn't clutter a windows procedure with dozens of conditionals and it address my primary objective of coding as tight as possible [28 bytes]. If you think my method can be improved upon in size and/or speed please post your solution.

Note: I have not tested this algorithym yet
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  1. ; 				      *** MESSAGE HANDLER ***
  2.  
  3. ; This procedure determines if application has a handler for a particular event.  All windows
  4. ; procedures are passed to this subroutine except those that have been sub or super classed.
  5.  
  6. ;	ENTRY:	ESI = Pointer to message map
  7. ;		ECX = Number of sets in map.
  8.  
  9. ; Each set consists of a 16 bit ID and 32 bit pointer to proceedure.
  10.  
  11. ;	LEAVE:	EAX = 0 if application handled event, or result of DefWindowProc is not.
  12. ; ____________________________________________________________________________________________		
  13.  
  14.   ; 		ESP +  0 = Return address in kernel module
  15.   ;		ESP +  4 = hWnd,	this windows 32 bit handle
  16.   ;		ESP +  8 = Msg,	Message ID passed by OS.
  17.   ;		ESP + 12 = wParam
  18.   ;		ESP + 16 = lParam
  19.  
  20.   MsgHandler		mov	edx, [esp + 8]	; Get message ID 0 - 1024 or user defined.
  21.  
  22. 	; In the unlikely event a null map is passed to this routine, this method of
  23. 	; testing ECX first will prevent a fatal crash.
  24.  
  25.   .NextMsg		and	ecx, ecx	; Are we at the end yet
  26. 			jz	.Default	; ZR = 1, If we are to do default proceesing.
  27.  
  28. 			dec	ecx		; Decrement counter
  29. 			lodsw			; Get 16 bit ID from message map
  30. 			cmp	 ax, dx		; Is there a match
  31. 			lodsd			; Load pointer
  32. 			jnz	.NextMsg
  33.  
  34.   	; At this point we've found a match and as many events need wParam & lParam,
  35. 	; I'm going to establish a pointer to those in EBX.  hWnd can be simply addressed
  36. 	; by EBX - 8 or lParam by EBX + 4.
  37.  
  38. 			lea	ebx, [esp + 12]	; EBX points to wParam
  39. 			call	eax		; Execute event
  40. 			jnc	.Default	; CY = 0, if event requires default proc.
  41.                                       xor         eax,  eax             ; Handled must return 0
  42. 			ret	16		; Stack needs to be re-aligned.
  43.  
  44.   	; As hWnd, Msg, wParam & lParam are already on the stack I use this method
  45. 	; as a trace into kernel showed OS handles this appropriately and there is no
  46. 	; point pushing onto stack what is already there.  I've tested this on 98/ME/XP.
  47.  
  48.   .Default		pop	ebx
  49. 			call	_DefWindowProcA@16
  50. 			jmp	ebx
  51.  
  52.   ; You'll notice at this point we don't need RET 16 as the call to DefWindowProc has already
  53.   ; done that for us.  
  54.  
  55.  

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