XmResolveAllPartOffsets(library call) XmResolveAllPartOffsets(library call)
NAMEXmResolveAllPartOffsets — A function that allows writing of upward-com‐
patible 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This routine is obsolete and exists for compatibility with pre‐
vious releases. You should call XmeResolvePartOffsets instead.
The use of offset records requires two extra global variables per wid‐
get 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 wid‐
get'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:
· Adds the superclass (which, by definition, has already been ini‐
tialized) size field to the part size field
· If the widget is a subclass of the Constraint class, adds the
superclass constraint size field to the constraint size field
· Allocates an array based upon the number of superclasses
· If the widget is a subclass of the constraint class, allocates an
array for the constraint offset record
· 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
· 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 struc‐
ture 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) argu‐
ment, 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 INFORMATIONXmResolvePartOffsets(3).
XmResolveAllPartOffsets(library call)
