DPMSQueryExtension - queries the X server to determine the availability of the
  DPMS Extension
cc [ flag ... ] file ... -lXext [ library ... ]
#include <X11/extensions/dpms.h>
Bool DPMSQueryExtension
(
      Display *display,
      int *event_base,
      int *error_base
);
  - display
- Specifies the connection to the X server
- event_base
- Specifies the return location for the assigned base event
- error_base
- Specifies the return location for the assigned base error
The DPMSQueryExtension function queries the X server to determine the
  availability of the Display Power Management Signaling (DPMS) Extension. If
  the extension is available, it returns TRUE, and the event_base and
  error_base are set to the base event and error numbers, respectively.
  Otherwise, the return value is FALSE, and the values of event_base and
  error_base are undefined.
  - TRUE
- The DPMSQueryExtension function returns TRUE if the extension is
      available, and event_base and error_base are set to the base
      event number and base error number for the extension, respectively.
- FALSE
- The DPMSQueryExtension function returns FALSE if extension is not
      available, and the values of event_base and error_base are
      undefined.