TutOptionChangeCbCreate

TutOptionChangeCbCreate — create a callback that is called when an option value changes

Synopsis

T_CB TutOptionChangeCbCreate(option, change_func, arg) 
T_OPTION option; 
T_OPTION_CHANGE_CB_FUNC change_func; 
T_CB_ARG arg;

Arguments

option — option to register the change callback for; NULL if callback is to be registered for all options

Return Values

Diagnostics

If TutOptionChangeCbCreate fails, it returns NULL and sets the global SmartSockets error number to one of:

T_ERR_NULL_PTR — change_func argument was NULL

T_ERR_ALREADY_EXISTS — a callback with change_func and arg already exists

Description

TutOptionChangeCbCreate attaches the change_func callback to option. When the value of option changes, change_func is called with three arguments:

option — option whose value changed

data — pointer to callback data structure

arg — callback function argument

Caution

The T_ENTRY declaration specifier is required in the definition of all callback functions as well as their prototypes.

See Also

Examples

/* This callback function is called when the */ 
/* value of option "bool_opt" changes. */ 
void T_ENTRY BoolChanged(option, data, arg)  
T_OPTION option; 
T_OPTION_CHANGE_CB_DATA data; 
T_CB_ARG arg; 
{ 
  T_BOOL bool_return; 
 
  if (!TutOptionGetBool(option, &bool_return)) { 
    /* error */ 
  } 
  if (bool_return) { 
    TutOut("Value of option %s is TRUE\n", 
TutOptionGetName(option)); 
  }  
  else { 
    TutOut("Value of option %s is FALSE\n", 
TutOptionGetName(option)); 
  }  
} /* BoolChanged */ 
 
/* Below is a code fragment that could go into an initialization routine. */ 
T_OPTION option; 
T_CB cb; 
 
option = TutOptionCreate("bool_opt", T_OPT_TYPE_BOOLEAN); 
if (option == NULL) { 
  /* error */ 
} 
 
cb = TutOptionChangeCbCreate(option, BoolChanged, NULL); 
if (cb == NULL) { 
  /* error */ 
}