C++ Changing Screen Orientation Issue -- DEVMODE dmDisplayOrientation DMDO_90 undefined

Question

I can't seem to get some C++ code to compile. I am flip the orientation of the display, but VS2008 is telling me the DMDO_90 and DMDO_270 are unidentified:

error C2065: 'DMDO_90' : undeclared identifier
error C2065: 'DMDO_270' : undeclared identifier

Am I missing something-- an include or something? According to the MSDN DEVMODE structure DMDO should be defined (under the dmDisplayOrientation section)--
Here is the code I have:

#include <iostream>
#include <string>
#include <windows.h>
using namespace std;

DISPLAY_DEVICE GetPrimaryDevice()
{
    int index=0;
    DISPLAY_DEVICE dd;
    dd.cb = sizeof(DISPLAY_DEVICE);

    while (EnumDisplayDevices(NULL, index++, &dd, 0))
    {
        if (dd.StateFlags & DISPLAY_DEVICE_PRIMARY_DEVICE) return dd;
    }
    return dd;
}

BOOL SetDisplayResolution(long degrees)
{
    DISPLAY_DEVICE dd = GetPrimaryDevice();
    DEVMODE dm;
    ZeroMemory(&dm, sizeof(dm));
    dm.dmSize = sizeof(DEVMODE);
    if (!EnumDisplaySettings(dd.DeviceName, ENUM_CURRENT_SETTINGS, &dm))
    {
        printf("EnumDisplaySettings failed:%d\n", GetLastError());
        return FALSE;
    }
    switch(degrees)
    {
    case 90:
        dm.dmDisplayOrientation = DMDO_90; //error C2065: 'DMDO_90' : undeclared identifier
        break;
    case 270:
        dm.dmDisplayOrientation = DMDO_270; //error C2065: 'DMDO_90' : undeclared identifier
        break;
    default:
        break;

    }
    DWORD dwTemp = dm.dmPelsHeight;
    dm.dmPelsHeight = dm.dmPelsWidth;
    dm.dmPelsWidth = dwTemp;

    dm.dmFields = (DM_PELSWIDTH | DM_PELSHEIGHT);
    if (ChangeDisplaySettings(&dm, CDS_TEST) !=DISP_CHANGE_SUCCESSFUL)
    {
        printf("\nIllegal graphics mode: %d\n", GetLastError());
        return FALSE;
    }

    return (ChangeDisplaySettings(&dm, 0)==DISP_CHANGE_SUCCESSFUL);
}

int main()
{
    if (SetDisplayResolution(90))
    { 
        return true;
    }
    else
    {
        return false;
    }

}

Answer 1

I am using VS 2008, and this constant is defined in wingdi.h (please use the Intellisense or a good code tagger such as Visual Assist to show you where these constants are defined).

The relevant part of the wingdi.h header is this:

#if(WINVER >= 0x0501)
/* DEVMODE dmDisplayOrientation specifiations */
#define DMDO_DEFAULT    0
#define DMDO_90         1
#define DMDO_180        2
#define DMDO_270        3

Note that WINVER has to be >= 0x0501, therefore more than likely you need to set the WINVER preprocessor symbol correctly.

Please see this link to modify WINVER: http://msdn.microsoft.com/en-us/library/6sehtctf.aspx