Getting information for a specific gadget.
------------------------------------------

The following #defines are taking from VisualArts.h file included with
Visual Arts.

#define GetString(gad)	        (((struct StringInfo *)gad->SpecialInfo)->Buffer)
#define GetUndoString(gad)	(((struct StringInfo *)gad->SpecialInfo)->UndoBuffer)
#define GetNumber(gad)	        (((struct StringInfo *)gad->SpecialInfo)->LongInt)

gad - is the gadget structure name to pass to.

1. GetString() function will return the string for the GadTool STRING_KIND

   eg: 
   
   #define ID_name                      1   //defined by Visual Arts
   #define ID_age                       2   //defined by Visual Arts
   struct Gadget *DemoGadgets[5];           //defined by Visual Arts
   char myvar[80];
   
   strcpy(myvar, GetString(DemoGadgets[ID_name]));
   
   this will copy the string in DemoGadget into myvar.  Note that the
   contants 'ID_name' and DemoGadgets[] is defined by Visual Arts.
   
2. GetNumber() function will return the number for the GadTool INTEGER_KIND

   eg: 
   
   #define ID_name                     1   //defined by Visual Arts
   #define ID_age                      2   //defined by Visual Arts
   struct Gadget *DemoGadgets[5];          //defined by Visual Arts
   int myinteger;
   
   myinteger = GetNumber(DemoGadgets[ID_age]);
   
   this will copy the string in DemoGadget into myvar.  Note that the
   contants 'ID_age' and DemoGadgets[] is defined by Visual Arts.


3. GetUndoString() function will return the undo string for the GadTool 
   STRING_KIND.  This is handy if the user types over the string gadget and
   you want to undo because they have entered a invalid entry.

   char undo[255];
   
   //get the previous name
   strcpy(undo, GetUndoString(DemoGadgets[ID_name]));
   
   //set the string gadget back to the previous name
   GT_SetGadgetAttrs(DemoGadgets[ID_name], DemoWnd, NULL,
 	GTST_String, undo, TAG_END);

4. Get the item selected from a ListView, Cycle, Popup and MX gadgets.

example:

//Visual Arts message object.  This structure gets passed to every active
//GadTool

struct VAobject {
  struct Window *va_Window;             //window the object originated
  struct Gadget *va_Gadget;             //the gadget that sent this object
  struct IntuiMessage *va_IntuiMsg;     //the IntuiMessage
  ULONG va_Flags;                       //user flags 
  APTR va_UserData;                     //user data, function pointer etc..
};


/*
   for ListView, Cycle, Popup and MX gadgets the VAObject.va_IntuiMsg->Code
   always contain the item the user selected, and you have always check
   this field when the user selects the gadget.
*/
int listviewObj(struct VAobject VAObject)
{
  int item;
  
  //get the item selected by the user
  item = VAObject.va_IntuiMsg->Code;      //get the item here!!!!
  printf("you selected item %d\n", item);
  
  return(1L);
}

5. Get from check boxes

int SmokerObj(struct VAobject VAObject)
{
  if (VAObject.va_Gadget->Flags & GFLG_SELECTED) //check if its checked
    printf("this person is a smoker\n");
  else
    printf("this person does not smoke\n");
  return(1L);
}
/*	Check Box  Cool!		 */ 


6. Setting GadTools.  For GadTools always use the  GT_SetGadgetAttrs()
   function and never use the anyother method.

   to disable any GadTool use.  Note you can't disable listview and mx
     
   //disable gadget
   GT_SetGadgetAttrs(DemoGadgets[ID_save], DemoWnd, NULL,
 	GA_Disabled, TRUE, TAG_END);

a. string gadgets

   GT_SetGadgetAttrs(DemoGadgets[ID_name], DemoWnd, NULL,
 	GTST_String, "Joe Blow", TAG_END);

   GT_SetGadgetAttrs(DemoGadgets[ID_name], DemoWnd, NULL,
 	GTST_String, myname, TAG_END);

b. integer gadgets

   GT_SetGadgetAttrs(DemoGadgets[ID_age], DemoWnd, NULL,
 	GTIN_Number, "Joe Blow", TAG_END);

   GT_SetGadgetAttrs(DemoGadgets[ID_age], DemoWnd, NULL,
 	GTST_Number, yourage, TAG_END);

c. checkbox gadgets

   //no check mark
   GT_SetGadgetAttrs(DemoGadgets[ID_smoker], DemoWnd, NULL,
 	GTCB_Checked, FALSE, TAG_END);

   //check mark
   GT_SetGadgetAttrs(DemoGadgets[ID_smoker], DemoWnd, NULL,
 	GTCB_Checked, TRUE, TAG_END);

d. mx gadgets

   eg:  
         0 - Male
         1 - Female
 
   //set it to Female
   GT_SetGadgetAttrs(DemoGadgets[ID_sex], DemoWnd, NULL,
 	GTMX_Active, 1 , TAG_END);

   //set it to Male
   GT_SetGadgetAttrs(DemoGadgets[ID_sex], DemoWnd, NULL,
 	GTMX_Active, 0 , TAG_END);

e. cycle gadgets

   eg: 
   
      Canada    = 0
      China     = 1
      .
      .
      USA       = 5
      
   //set the cycle to be USA
   GT_SetGadgetAttrs(DemoGadgets[ID_country], DemoWnd, NULL,
 	GTCY_Active, 5 , TAG_END);

f. slider

   min = 10000
   max = 50000
   
   //set the level to 30000
   GT_SetGadgetAttrs(DemoGadgets[ID_salary], DemoWnd, NULL,
 	GTSL_Level, 30000 , TAG_END);

g. scroller

   top = 1
   total = 10
      
   //set the top to start displaying from 5
   GT_SetGadgetAttrs(DemoGadgets[ID_salary], DemoWnd, NULL,
 	GTSC_Top, 5 , TAG_END);

h. listview

//defined by Visual Arts in your project header file .h

struct List *DemoLists[2];

//this will attach list 1 
   GT_SetGadgetAttrs(DemoGadgets[ID_names], DemoWnd, NULL,
 	GTLV_Label, DemoLists[1] , TAG_END);


To better understand GadTools you should read the RKM in the GadTool
section.  It is very informative.