hpux man page for xtresourcedefaultproc

XtResourceDefaultProc() 												   XtResourceDefaultProc()

Name
  XtResourceDefaultProc - interface definition for procedure called to obtain a resource default value.

Synopsis
  typedef void (*XtResourceDefaultProc)(Widget, int, XrmValue *)
	 Widget w;
	 int offset;
	 XrmValue *value_return;

Inputs
  w	    Specifies the widget whose resource is to be obtained.

  offset    Specifies the offset of the field in the widget record.

Outputs
  value_return
	 Returns the address of the default resource value.

Description
  An  XtResourceDefaultProc  is  registered in an XtResource structure of an XtResourceList array by specifying the special value XtRCallProc
  for the default_type field, and specifying the procedure in the default_addr field.  It is called by the Intrinsics when the default	value
  of that resource is required.

  An  XtResourceDefaultProc  should  determine	the default value of the resource, convert it to the correct type if necessary, and store the
  address of the value at value_return->addr.  It need not store the size of this value because the resource manager already knows  the  size
  of the resource.

  See XtGetApplicationResources(1) for more information on the fields of the XtResource structure and an example of how to declare one.

Usage
  An  XtResourceDefaultProc  is  passed the offset of the resource field in the widget or object w as its offset argument.  It should not use
  this argument to set the resource value directly in the object.  It can use it to identify which resource value is  desired,	if  the  same
  procedure  is  used  to  obtain default values for more than one resource.  It can also be used to obtain the same resource value from some
  other already initialized widget of the same class, as is shown in the example below.

Example
  The default value for the XtNdepth resource of the Core widget class should be whatever value the widget's parent has.  To implement	this,
  the XtNdepth resource is declared with an XtResourceDefaultProc as follows:

     {XtNdepth, XtCDepth, XtRInt,sizeof(int),
	  XtOffsetOf(CoreRec,core.depth),
	  XtRCallProc, (XtPointer)_XtCopyFromParent},

  The _XtCopyFromParent() XtResourceDefaultProc is defined by the Intrinsics as follows.  Note how the resource value is returned and how the
  offset argument is used.

     void _XtCopyFromParent(widget, offset, value)
	 Widget      widget;
	 int	     offset;
	 XrmValue    *value;
     {
	 if (widget->core.parent == NULL) {
	     XtAppWarningMsg(XtWidgetToApplicationContext(widget),
			     "invalidParent","xtCopyFromParent",
			     XtCXtToolkitError,
			     "CopyFromParent must have non-NULL parent",
			     (String *)NULL, (Cardinal *)NULL);
	     value->addr = NULL;
	     return;
	 }
	 value->addr = (XPointer)(((char *)widget->core.parent) + offset);
     }

See Also
  XtGetApplicationResources(1), XtGetSubresources(1).

Xt - Resource Management												   XtResourceDefaultProc()