How to adjust monitor brightness (Vista, monitor with DDC support) using Visual Foxpro

The Monitor Configuration API was first made available in Windows Vista. These functions are applicable only if the monitor supports the Display Data Channel (DDC/CI) connection with the graphics adapter.

At least thirteen Monitor Configuration functions exist. Those include GETs and/or SETs for brightness, color temperature, contrast, display area position & size, factory defaults and more. Some models may have limited Monitor Configuration support.

The following code sample includes calls to several Monitor Configuration functions, in particular those reading and changing the brightness of a monitor.

#DEFINE MONITOR_DEFAULTTONEAREST 2 
DO declare   

LOCAL hMonitor, cMonitorName, hPhysMonitor,;     
nPhysMonitorCount, cPhysMonitorArray, nResult   

* find out on which monitor 
* the main VFP window resides 

hMonitor = MonitorFromWindow(_vfp.hWnd,;     
MONITOR_DEFAULTTONEAREST)   

* find out the number of physical monitors 
* associated with the hMonitor 

handle nPhysMonitorCount=0 
= GetNumberOfPhysicalMonitorsFromHMONITOR(hMonitor,;     
  @nPhysMonitorCount)   
  
IF nPhysMonitorCount = 0     
 ? "No physical monitor detected."     
 RETURN 
ENDIF   

* allocate space for the array 
* of PHYSICAL_MONITOR structures 
cPhysMonitorArray = REPLICATE(CHR(0), 4096)   

* retrieves the physical monitors data 
nResult = GetPhysicalMonitorsFromHMONITOR(hMonitor,;     
nPhysMonitorCount, @cPhysMonitorArray)   
IF nResult = 0    
 ? "GetPhysicalMonitorsFromHMONITOR() failed:",;         
 GetLastError()     
 RETURN 
ENDIF   

* this pseudo-handle starts with 0 and increments 
* for each following physical monitor 
hPhysMonitor = buf2dword(SUBSTR(cPhysMonitorArray, 1,4)) 
? "Physical Monitor handle:", hPhysMonitor   
cMonitorName = SUBSTR(cPhysMonitorArray, 5) 
cMonitorName = SUBSTR(m.cMonitorName, 1,;     
AT(CHR(0)+CHR(0), cMonitorName)) 
? "Monitor name:", STRCONV(cMonitorName,6)   

LOCAL capMonitor, capColorTemp 
STORE 0 TO capMonitor, capColorTemp   

* takes about a second to return 
IF GetMonitorCapabilities(hPhysMonitor,;     
  @capMonitor, @capColorTemp) <> 0     
  ? "Monitor Cap flags:", capMonitor     
  ? "Monitor Color Temp flags:", capColorTemp 
ENDIF   

LOCAL minBrightness, curBrightness, maxBrightness 
STORE 0 TO minBrightness, curBrightness, maxBrightness   

* retrieving the brightness value (%) for the monitor 
IF GetMonitorBrightness(hPhysMonitor,;     
 @minBrightness, @curBrightness, @maxBrightness) <> 0       
 ? "Brightness min, current, max:",;        
 minBrightness, curBrightness, maxBrightness       
 
 * setting the brightness     
 * uncomment to try     * 
 = SetMonitorBrightness(hPhysMonitor, 100) ELSE     
 ? "GetMonitorBrightness() failed:",;         
 GetLastError() 
ENDIF   

* this is the must on exit: closes the array of open 
* physical monitor 
  handles = DestroyPhysicalMonitors(nPhysMonitorCount,;     
    @cPhysMonitorArray)   
* end of main   
  

  PROCEDURE declare     
     DECLARE INTEGER MonitorFromWindow IN user32;        
	 INTEGER hWindow, INTEGER dwFlags      
	 DECLARE INTEGER GetLastError IN kernel32      
	 DECLARE INTEGER GetMonitorCapabilities IN dxva2;      
	 INTEGER hMonitor, LONG @pdwMonitorCapabilities,;      
	 LONG @pdwSupportedColorTemperatures    
	 DECLARE INTEGER GetPhysicalMonitorsFromHMONITOR IN dxva2;     
	 INTEGER hMonitor, LONG dwPhysicalMonitorArraySize,;       
	 STRING @pPhysicalMonitorArray       
	 DECLARE INTEGER GetNumberOfPhysicalMonitorsFromHMONITOR IN dxva2;        
	 INTEGER hMonitor, LONG @pdwNumberOfPhysicalMonitors      
	 DECLARE INTEGER DestroyPhysicalMonitors IN dxva2;      
	 LONG dwPhysicalMonitorArraySize, STRING @pPhysicalMonitorArray  
     DECLARE INTEGER GetMonitorBrightness IN dxva2;       
	 INTEGER hMonitor, LONG @pdwMinimumBrightness,;       
	 LONG @pdwCurrentBrightness, LONG @pdwMaximumBrightness     
	 DECLARE INTEGER SetMonitorBrightness IN dxva2;        
	 INTEGER hMonitor, LONG dwNewBrightness   
	 
	 FUNCTION buf2dword(cBuffer) RETURN Asc(SUBSTR(cBuffer, 1,1)) + ;     
	    BitLShift(Asc(SUBSTR(cBuffer, 2,1)),  8) +;     
		BitLShift(Asc(SUBSTR(cBuffer, 3,1)), 16) +;     
		BitLShift(Asc(SUBSTR(cBuffer, 4,1)), 24) 

}