Camera API Technical Report:
Example Code

Example Code

#include <stdio.h>
#include <X11/Intrinsic.h>
#include <camera.h>

/* define the camera set value callback. The procedure is provided
   with camera pointer, the data pointer installed with the callback
   and the value type of the set attribute */
void camera_controls_callback( camera, client_data, val_type )
Camera          camera;
XtPointer       *client_data;
CameraValueType val_type;
{
    Widget              controls = (Widget) client_data;

    switch( val_type ){         /* test for values in the dialog */
    case CV_X_Binning:
    case CV_Y_Binning:
        /* reset the interface etc */
        break;
    .
    .
    .
    }

    return;
}
 
/* define a camera error handler. The procedure is provided with the
   camera pointer, the data pointer installed with the handler and
   a pointer to an error data structure. */
static int camera_error_handler( cam, data, error )
Camera          cam;
caddr_t         data;
CameraError     *error;
{
    Widget      dialog = (Widget) data;
    String      str;

    str = (String) malloc(sizeof(char) *
                          (strlen(CameraName(cam)) +
                           strlen(error->srcstr) +
                           strlen(error->errstr) + 40));
    (void) sprintf(str, "%s camera error\nsource: %s\nerror: %s",
                   CameraName(cam), error->srcstr, error->errstr);
    HGU_XmUserError( dialog, str, 0 );
    free( str );
}


.
.
    Camera		camera;

    /* open the camera initialise etc. etc. */

    /* create the camera interface */
    dialog = create_camera_interface( camera );

    /* add an error handler */
    CameraSetErrHandler( camera, camera_error_handler, dialog );

    /* add a callback to the camera to reset interface values */
    CameraAddSetCallback( camera, camera_controls_callback, dialog );
.
.

The CameraError structure contains an error-string, a source-string and an error number. In this version of the library the error number is not used.

Note the SetCallback is a callback list. Any number of functions can be added to the list and will be called in the order they were added to the list.