XmResolveAllPartOffsets(library call)

NAME

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

SYNOPSIS

#include <Xm/Xm.h>
void XmResolveAllPartOffsets(
WidgetClass widget_class,
XmOffsetPtr * offset,
XmOffsetPtr * constraint_offset);

DESCRIPTION

Note:

This routine is obsolete and exists for compatibility with
previous releases. You should call XmeResolvePartOffsets
instead.

The use of offset records requires two extra global variables per
widget class. The variables consist of pointers to arrays of offsets
into the widget record and constraint record for each part of the
widget structure. The XmResolveAllPartOffsets function allocates the
offset records needed by an application to guarantee upward-
compatible access to widget instance and constraint 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 steps described in the following paragraphs.

Instead of creating a resource list, the widget creates an offset
resource list. To 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 structure 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.

If the widget is a subclass of the Constraint class and it defines
additional constraint resources, create an offset resource list for
the constraint part as well. Instead of using XtOffset for the
offset, the widget uses XmConstraintPartOffset in the constraint
resource list.

XmPartResource resources[] = {
{ BarNxyz, BarCXyz, XmRBoolean, sizeof(Boolean),
XmPartOffset(Bar,xyz), XmRImmediate, (XtPointer)False } };
XmPartResource constraints[] = {
{ BarNmaxWidth, BarNMaxWidth,
XmRDimension, sizeof(Dimension),
XmConstraintPartOffset(Bar,max_width),
XmRImmediate, (XtPointer)100 } };

Instead of putting the widget size in the class record, the widget
puts the widget part size in the same field. If the widget is a
subclass of the Constraint class, instead of putting the widget
constraint record size in the class record, the widget puts the
widget constraint part size in the same field.

Instead of putting XtVersion in the class record, the widget puts
XtVersionDontCheck in the class record.

Define a variable, of type XmOffsetPtr, to point to the offset
record. If the widget is a subclass of the Constraint class, define
a variable of type XmOffsetPtr to point to the constraint offset
record. These can be part of the widget's class record or separate
global variables.

In class initialization, the widget calls XmResolveAllPartOffsets,
passing it pointers to the class record, the address of the offset
record, and the address of the constraint offset record. If the
widget not is a subclass of the Constraint class, it should pass NULL
as the address of the constraint offset record. This does several
things:

+o Adds the superclass (which, by definition, has already been
initialized) size field to the part size field

+o If the widget is a subclass of the Constraint class, adds the
superclass constraint size field to the constraint size field

+o Allocates an array based upon the number of superclasses

+o If the widget is a subclass of the constraint class, allocates
an array for the constraint offset record

+o Fills in the offsets of all the widget parts and constraint
parts with the appropriate values, determined by examining the
size fields of all superclass records

+o Uses the part offset array to modify the offset entries in the
resource list to be real offsets, in place

The widget defines a constant that 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 superclass. 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 and XmConstraintField macros
help you access these fields. Because the XmPartOffset,
XmConstraintPartOffset, XmField, and XmConstraintField macros
concatenate things, 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)))

For constraint field max_width:

#define BarMaxWidth(w) \
XmConstraintField(w,constraint_offsets,Bar,max_width,Dimension)

The parameters for XmResolveAllPartOffsets are

widget_class
Specifies the widget class pointer for the created widget

offset Returns the offset record

constraint_offset
Returns the constraint offset record

RELATED INFORMATION

XmResolvePartOffsets(3).

XmResolveAllPartOffsets(library call)