Camera API Technical Report:
Errors and the Set Value Callback

Errors and the Set Value Callback

Errors can be trapped by installing an error handler. The default error handler simply prints a message to stderr. Any installed error handler can be retrieved if necessary. To switch off error reporting an error-handler which does nothing has to be installed. For more convenient OO type behavior of interfaces there is also provision for a callback function whenever an attribute is set.

#include <sys/types.h>
#include <camera.h>

int CameraSetErrorHandler( cam, handler, data )
Camera		cam;
int		(*handler)();
caddr_t         data;

int CameraGetErrorHandler( cam, handler, data )
Camera		cam;
int		(**handler)();
caddr_t         *data;

int CameraAddSetCallback( cam, callback, data )
Camera		cam;
void		(*callback)();
caddr_t         data;

int CameraRemoveSetetCallback( cam, callback, data )
Camera		cam;
void		(*callback)();
caddr_t         data;

int CameraCallSetCallbacks( cam, val_type )
Camera	        *cam;
CameraValueType	val_type;

Each function is installed with the option of a single pointer to data to be provided when the handler or callback is called. The code fragment below shows how these functions can be used.