NAME
	GU_GetGadgetPtr -- Get a pointer to a gadget's gadget structure.

   SYNOPSIS
	gad = GU_GetGadgetPtr(id, gadgets)
	D0,SR(Z)              D0  A0

	APTR GU_GetGadgetPtr(UWORD, struct LayoutGadget *);

   FUNCTION
	Find a gadget's gadget structure by giving its ID. The gadget
	pointer is always found last in the LayoutGadget structure. You
	can use this function to get that pointer.
	It is also possible to get the gadget structure by taking it
	directly from the LayoutGadget structure array, but then you
	must know exactly in which structure it is located. Assembly
	language programmers can use a PC relative pointer to get the
	gadget pointer.
	
   INPUTS
	id - the ID of the gadget to search for

	gadgets - a pointer to the array of LayoutGadget structures.

   RESULT
	gad - pointer to the requested gadget. For bevelboxes, this
	      function will return a BBoxData structure. A ProgressGad
	      structure is returned for a progress display gadget.

   EXAMPLE

     Some of the LayoutGadget structures from BetterTest.c:

     struct LayoutGadget gadgets[] = {
	{ MSG_NEXTDRIVE, NextDriveGad, StdGTTags,   NULL },
	{ MSG_PREVDRIVE, PrevDriveGad, StdGTTags,   NULL },
	{ MSG_DRIVE,	 DriveGad,     DriveGTTags, NULL },
	{ MSG_REQUESTER, ReqGad,       StdGTTags,   NULL },
	{ MSG_CHECKME,   CheckBoxGad,  StdGTTags,   NULL },
	{ MSG_FILENAME,  FileNameGad,  StdGTTags,   NULL },
	{ -1,            NULL,         NULL,        NULL }
     };

	The examples should get the gadget structure of the Requester
	gadget (not assuming that ID's begin with 0).
	There is two methods you can use to get a gadgets structure:

	1. Use the pointer in the array directly:

	thegadget = gadgets[3].lg_Gadget

	This will only work if you know in which LayoutGadget structure
	the gadget is in.

	2. Use this library function:

	thegadget = GU_GetGadgetPtr(MSG_REQUESTER, gadgets);

	This will always work if all gadgets have a unique ID.


     Some of the LayoutGadget structures from BetterTest.s:

	gadgets:
	 GADGET  MSG_NEXTDRIVE,  NextDriveGad,   StdGTTags
	 GADGET  MSG_PREVDRIVE,  PrevDriveGad,   StdGTTags
	 GADGET  MSG_DRIVE,      DriveGad,       DriveGTTags
	 GADGET  MSG_REQUESTER,  ReqGad,         StdGTTags
	 GADGET  MSG_CHECKME,    CheckBoxGad,    StdGTTags
	 GADGET  MSG_FILENAME,   FileNameGad,    StdGTTags
	 GADGET  -1,NULL,NULL

     Assembly language programmers can use three methods to get the
     pointer:

	1. Use the pointer in the array directly:

		lea.l	gadgets(pc),a0	; Get array
		moveq.l	#lg_SIZEOF,d0	; Get the size of the LayoutGadget
		mulu	#3,d0		;  struct and calculate offset to
					;  the right structure in the array
		move.l	lg_Gadget(a0,d0.l),d0	; Get the gadget pointer

	This will only work if you know in which LayoutGadget structure
	the gadget is in.

	2. Use this library function:

		lea.l	gadgets(pc),a0	; Get array
		moveq.l	#MSG_REQUESTER,d0	; Gadget to search for
		jsr	_LVOGU_GetGadgetPtr(a6)	; Get gadget, result in D0

	This will always work if all gadgets have a unique ID.

	3. Use an extra label for each gadget that should be easy to
	   access:

	gadgets:
	 GADGET  MSG_NEXTDRIVE,  NextDriveGad,   StdGTTags
	 GADGET  MSG_PREVDRIVE,  PrevDriveGad,   StdGTTags
	 GADGET  MSG_DRIVE,      DriveGad,       DriveGTTags
	 GADGET  MSG_REQUESTER,  ReqGad,         StdGTTags
	reqgad:		equ	*-4
	 GADGET  MSG_CHECKME,    CheckBoxGad,    StdGTTags
	 GADGET  MSG_FILENAME,   FileNameGad,    StdGTTags
	filenamegad:	equ	*-4
	 GADGET  -1,NULL,NULL

		move.l	reqgad(pc),d0		; Get the gadget

	This will always work.

Converted on 19 Jul 1996 with RexxDoesAmigaGuide2HTML by Michael Ranner.