ChangeDisplaySettingsEx
The ChangeDisplaySettingsEx function changes the settings of the specified display device to the specified graphics mode.
LONG ChangeDisplaySettingsEx(
LPCTSTR lpszDeviceName, // name of display device
LPDEVMODE lpDevMode, // graphics mode
HWND hwnd, // not used; must be NULL
DWORD dwflags, // graphics mode options
LPVOID lParam // video parameters (or NULL)
);
Parameters
lpszDeviceName
[in] Pointer to a null-terminated string that specifies the display device whose graphics mode the function will obtain information about. Only display device names as returned by EnumDisplayDevices are valid. 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. The default device can be determined by calling EnumDisplayDevices and checking for the DISPLAY_DEVICE_PRIMARY_DEVICE flag.
lpDevMode
[in] Pointer to a DEVMODE structure that describes the new graphics mode. 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.
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. In addition, you can use any of 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 Position of the device in a multi-monitor configuration.
In addition to using one or more of the preceding DEVMODE members, you must also set one or more of the following values in the dmFields member to change the display settings. Value 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 Use the dmPosition value.
hwnd
Reserved; must be NULL.
dwflags
[in] Indicates how the graphics mode should be changed. This parameter can be one of the following values. Value Meaning
0 The graphics mode for the current screen will be changed dynamically.
CDS_FULLSCREEN The mode is temporary in nature.
Windows NT/2000 or later: 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_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.
CDS_RESET The settings should be changed, even if the requested settings are the same as the current settings.
CDS_SET_PRIMARY This device will become the primary device.
CDS_TEST The system tests if the requested graphics mode could be set.
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_VIDEOPARAMETERS When set, the lParam parameter is a pointer to a VIDEOPARAMETERS structure.
Specifying CDS_TEST allows an application to determine which graphics modes are actually valid, without causing the system to change to them.
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/2000 or later: 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
[in] If dwFlags is CDS_VIDEOPARAMETERS, lParam is a pointer to a VIDEOPARAMETERS structure. Otherwise lParam must be NULL.
Return Values
The ChangeDisplaySettingsEx function returns one of the following values.
Value Meaning
DISP_CHANGE_SUCCESSFUL The settings change was successful.
DISP_CHANGE_BADDUALVIEW Whistler: The settings change was unsuccessful because the system is DualView capable.
DISP_CHANGE_BADFLAGS An invalid set of flags was passed in.
DISP_CHANGE_BADMODE The graphics mode is not supported.
DISP_CHANGE_BADPARAM An invalid parameter was passed in. This can include an invalid flag or combination of flags.
DISP_CHANGE_FAILED The display driver failed the specified graphics mode.
DISP_CHANGE_NOTUPDATED Windows NT/2000 or later: Unable to write settings to the registry.
DISP_CHANGE_RESTART The computer must be restarted for the graphics mode to work.
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 adding a display monitor to a multiple-monitor system programmatically, set DEVMODE.dmFields to DM_POSITION and specify a position (in DEVMODE.dmPosition) for the monitor you are adding that is adjacent to at least one pixel of the display area of an existing monitor. To detach the monitor, set DEVMODE.dmFields to DM_POSITION but set DEVMODE.dmPelsWidth and DEVMODE.dmPelsHeight to zero. For more information, see Multiple Display Monitors.
When the display mode is changed dynamically, the WM_DISPLAYCHANGE message is sent to all running applications with the following message parameters.
Parameters Meaning
wParam New bits per pixel
LOWORD(lParam) New pixel width
HIWORD(lParam) New pixel height
Requirements
Windows NT/2000 or later: Requires Windows 2000 or later.
Windows 95/98/Me: Requires Windows 98 or later.
Header: Declared in Winuser.h; include Windows.h.
Library: Use User32.lib.
Unicode: Implemented as Unicode and ANSI versions on Windows 2000.
