How to identify inside screen resolution the multiple display that is enabled?

Question

I've searched all over Google but found no answer, so If someone knows It would be very thankful!

I want to use command line or some WinApi to check the state of the multiple display. For example : If I set : "extended screen" or "duplicate screen" I want to be able to verify it. Just have no idea where to start.

thanks a lot

Answer 1

I would start with the WinAPI EnumDisplayMonitors function: http://msdn.microsoft.com/en-us/library/dd162610%28VS.85%29.aspx

BOOL EnumDisplayMonitors(
  _In_  HDC hdc,
  _In_  LPCRECT lprcClip,
  _In_  MONITORENUMPROC lpfnEnum,
  _In_  LPARAM dwData
);

You need to call this function setting the first 2 parameters to NULL like this:

EnumDisplayMonitors(NULL, NULL, MyPaintEnumProc, 0);

//Enumerates all display monitors.
//The callback function receives a NULL HDC.

Now you have your MonitorEnumProc callback function: http://msdn.microsoft.com/en-us/library/dd145061%28v=vs.85%29.aspx

BOOL CALLBACK MonitorEnumProc(
  _In_  HMONITOR hMonitor,
  _In_  HDC hdcMonitor,
  _In_  LPRECT lprcMonitor,
  _In_  LPARAM dwData
);

You wiil get filled lprcMonitor back:

A pointer to a RECT structure. If hdcMonitor is non-NULL, this rectangle is the intersection of the clipping area of the device context identified by hdcMonitor and the display monitor rectangle. The rectangle coordinates are device-context coordinates.

If hdcMonitor is NULL, this rectangle is the display monitor rectangle. The rectangle coordinates are virtual-screen coordinates.

Based on this values for ALL monitors you can decide whether you have an extended mode (the rects are different) or the duplicate (they are equal).

HTH - good luck!