XmResolvePartOffsets(3X)												  XmResolvePartOffsets(3X)

NAME

       XmResolvePartOffsets - A function that allows writing of upward-compatible applications and widgets

SYNOPSIS

       #include <Xm/XmP.h>

       void XmResolvePartOffsets (widget_class, offset)
	       WidgetClass widget_class;
	       XmOffsetPtr * offset;

DESCRIPTION

       The  use  of  offset records requires one extra global variable per widget class. The variable consists of a pointer to an array of offsets
       into the widget record for each part of the widget structure. The XmResolvePartOffsets function allocates the offset records needed  by	an
       application to guarantee upward-compatible access to widget instance records by applications and widgets.  These offset records are used by
       the widget to access all of the widget's variables. A widget needs to take the following steps: Instead of creating a  resource	list,  the
       widget  creates	an  offset  resource  list.  To help you accomplish this, use the XmPartResource structure and the XmPartOffset macro. The
       XmPartResource data structure looks just like a resource list, but instead of having one integer for its offset, it has two shorts. This is
       put into the class record as if it were a normal resource list.	Instead of using XtOffset for the offset, the widget uses XmPartOffset.

	      XmPartResource resources[] = {
		{ BarNxyz, BarCXyz, XmRBoolean,
		  sizeof(Boolean), XmPartOffset(Bar,xyz),
		  XmRImmediate, (XtPointer)False } }; Instead of putting the widget size in the class record, the widget puts the widget part size
	      in the same field.  Instead of putting XtVersion in the class record, the widget puts XtVersionDontCheck in the class  record.   The
	      widget  defines  a  variable, of type XmOffsetPtr, to point to the offset record. This can be part of the widget's class record or a
	      separate global variable.  In class initialization, the widget calls XmResolvePartOffsets, passing  it  a  pointer  to  contain  the
	      address  of the offset record and the class record. This does several things: Adds the superclass (which, by definition, has already
	      been initialized) size field to the part size field.  Allocates an array based upon the number of superclasses.  Fills in  the  off-
	      sets  of	all the widget parts with the appropriate values, determined by examining the size fields of all superclass records.  Uses
	      the part offset array to modify the offset entries in the resource list to be real offsets.  The widget  defines	a  constant  which
	      will  be	the  index to its part structure in the offsets array. The value should be 1 greater than the index of the widget's super-
	      class. Constants defined for all Xm widgets can be found in <XmP.h>.

	      #define BarIndex (XmBulletinBIndex + 1) Instead of accessing fields directly, the widget must always go through  the  offset  table.
	      The  XmField  macro helps you access these fields. Because the XmPartOffset and XmField macros concatenate things together, you must
	      ensure that there is no space after the part argument. For example, the following macros do not work because of the space after  the
	      part (Label) argument:

	      XmField(w, offset, Label , text, char *) XmPartOffset(Label , text)

	      Therefore, you must not have any spaces after the part (Label) argument, as illustrated here:

	      XmField(w, offset, Label, text, char *)

	      You can define macros for each field to make this easier. Assume an integer field xyz:

	      #define BarXyz(w) (*(int *)(((char *) w) + 
		offset[BarIndex] + XtOffset(BarPart,xyz)))

       The  parameters	for XmResolvePartOffsets are defined below: Specifies the widget class pointer for the created widget.	Returns the offset
       record.

SEE ALSO

       XmResolveAllPartOffsets(3X)

															  XmResolvePartOffsets(3X)