ChangeDisplaySettingsEx

[This is preliminary documentation and subject to change.]

The ChangeDisplaySettingsEx function changes the settings of the display device specified in the lpszDeviceName parameter to the graphics mode specified in the lpDevMode parameter.

LONG ChangeDisplaySettingsEx(
  LPCSTR lpszDeviceName,
  LPDEVMODE lpDevMode,  
  HWND     hwnd,
  DWORD dwflags         
  LPVOID lParam
);
 

Parameters

lpszDeviceName

Pointer to a null-terminated string that specifies the display device whose graphics mode the function will obtain information about. See EnumDisplayDevices for further information on the names associated with these display devices.

The lpszDeviceName parameter can be NULL. A NULL value specifies the default display device.

lpDevMode

Pointer to a DEVMODE structure that describes the graphics mode to switch to. The dmSize member must be initialized to the size, in bytes, of the DEVMODE structure. The dmDriverExtra member must be initialized to indicate the number of bytes of private driver data following the DEVMODE structure.

You can use the following members of the DEVMODE structure.

Member	Meaning
dmBitsPerPel	Bits per pixel
dmPelsWidth	Pixel width
dmPelsHeight	Pixel height
dmDisplayFlags	Mode flags
dmDisplayFrequency	Mode frequency
dmPosition	Windows 98, Windows NT 5.0 and later: Position of the device in a multi-monitor configuration.

In addition to setting a value in one or more of the preceding DEVMODE members, you must also set the appropriate flags in the dmFields member. The flags indicate which members of the DEVMODE structure are used for the display settings change. If the appropriate bit is not set in dmFields, the display setting will not be changed. Set one or more of the following flags:

Flag	Meaning
DM_BITSPERPEL	Use the dmBitsPerPel value.
DM_PELSWIDTH	Use the dmPelsWidth value.
DM_PELSHEIGHT	Use the dmPelsHeight value.
DM_DISPLAYFLAGS	Use the dmDisplayFlags value.
DM_DISPLAYFREQUENCY	Use the dmDisplayFrequency value.
DM_POSITION	Windows 98, Windows NT 5.0 and later: Use the dmPosition value.

If lpDevMode is NULL, all the values currently in the registry will be used for the display setting. Passing NULL for the lpDevMode parameter and 0 for the dwFlags parameter is the easiest way to return to the default mode after a dynamic mode change.

hwnd

Must be NULL.

dwflags

Indicates how the graphics mode should be changed. The dwflags parameter can be one of the following.

Flag	Meaning
0	The graphics mode for the current screen will be changed dynamically.
CDS_UPDATEREGISTRY	The graphics mode for the current screen will be changed dynamically and the graphics mode will be updated in the registry. The mode information is stored in the USER profile.
CDS_TEST	The system tests if the requested graphics mode could be set.
CDS_FULLSCREEN	The mode is temporary in nature. Windows NT: If you change to and from another desktop, this mode will not be reset.
CDS_GLOBAL	The settings will be saved in the global settings area so that they will affect all users on the machine. Otherwise, only the settings for the user are modified. This flag is only valid when specified with the CDS_UPDATEREGISTRY flag.
CDS_SET_PRIMARY	This device will become the primary device.
CDS_RESET	The settings should be changed, even if the requested settings are the same as the current settings.
CDS_SETRECT	The lParam message parameter specified in the WM_DISPLAYCHANGE message sent to all applications should be treated as a pointer to a RECT structure. This structure indicates the position of the display device in a multi-screen environment. An lParam of NULL means that the display device should be detached from the multi-screen environment.
CDS_NORESET	The settings will be saved in the registry, but will not take effect. This flag is only valid when specified with the CDS_UPDATEREGISTRY flag.

Specifying CDS_TEST allows an application to determine which graphics modes are actually valid, without causing the system to change to that graphics mode.

If CDS_UPDATEREGISTRY is specified and it is possible to change the graphics mode dynamically, the information is stored in the registry and DISP_CHANGE_SUCCESSFUL is returned. If it is not possible to change the graphics mode dynamically, the information is stored in the registry and DISP_CHANGE_RESTART is returned.

Windows NT: If CDS_UPDATEREGISTRY is specified and the information could not be stored in the registry, the graphics mode is not changed and DISP_CHANGE_NOTUPDATED is returned.

lParam

Must be NULL.

Return Values

The ChangeDisplaySettingsEx function returns one of the following values.

Remarks

To ensure that the DEVMODE structure passed to ChangeDisplaySettingsEx is valid and contains only values supported by the display driver, use the DEVMODE returned by the EnumDisplaySettings function.

When the display mode is changed dynamically, the WM_DISPLAYCHANGE message is sent to all running applications with the following message parameters:

QuickInfo

  Windows NT: Requires version 5.0 or later.
  Windows: Requires Windows 98 or later.
  Windows CE: Unsupported.
  Header: Declared in winuser.h.
  Import Library: Use user32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also

Device Contexts Overview, Device Context Functions, ChangeDisplaySettings, CreateDC, DEVMODE, EnumDisplayDevices, EnumDisplaySettings, WM_DISPLAYCHANGE