Volume 7A: XView Programming Manual

25.4 XView Packages

Earlier, we introduced the concept of XView methods and how they are used to define the in-

teraction between a particular class and the XView intrinsics. These methods, along with a

set of attributes, macros, types, and functions, collectively make up an XView package. The

XView library is made up of statically subclassed (pre-built) packages representing user in-

terface objects.

25.4.1 The Xv_pkg Type

Packages (and thus, classes) are declared by creating a global variable of type Xv_pkg. This

package is defined in <xview/pkg_public.h> as:

typedef struct _xview_pkg {

char *name;

Attr_attribute attr_id;

unsigned size_of_object;

struct _xview_pkg *parent_pkg;

int (*init)();

Xv_opaque (*set)();

Xv_opaque (*get)();

int (*destroy)();

Xv_object (*find)();

} Xv_pkg;

The fields of the Xv_pkg type are declared and used as follows:

name The name of the package is a unique, descriptive string. This is useful

for debugging the ERROR package, and it may also be used in the fu-

ture to implement resource handling from the resource database.

Therefore, it should not contain whitespace or dots (periods). Under-

scores and hyphens are allowed, but should be avoided for aesthetic

reasons. A combination of uppercase and lowercase letters should be

used to imply multi-word names (e.g., “DigitalClock”).

attr_id This is the ID of the package. It is set to a unique number and is used

in attributes’ values to ...