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ChangeDisplaySettings

The ChangeDisplaySettings function changes the display settings to the specified graphics mode.

VB4-32,5,6
Declare Function ChangeDisplaySettings Lib "user32" Alias "ChangeDisplaySettingsA" (lpDevMode As Any, ByVal dwFlags As Long) As Long

Operating Systems Supported
Requires Windows NT 3.5(1) or later; Requires Windows 95 or later

Library
User32

Parameter Information
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 following fields in the DEVMODE structure are used:
dmBitsPerPel
Bits per pixel
dmPelsWidth
Pixel width
dmPelsHeight
Pixel height
dmDisplayFlags
Mode flags
dmDisplayFrequency
Mode frequency

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:
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_DISPLAYFREQENCY
Use the dmDisplayFrequency 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 is the easiest way to return to the default mode after a dynamic mode change.

dwflags
Indicates how the graphics mode should be changed. May be one of the following:
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.

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 the information could not be stored in the registry, the graphics mode is not changed and DISP_CHANGE_NOTUPDATED is returned.
Specifying CDS_TEST allows an application to determine which graphics modes are actually valid, without causing the system to change to that graphics mode.

Return Values
The ChangeDisplaySettings function returns one of the following values.

DISP_CHANGE_SUCCESSFUL The settings change was successful.
DISP_CHANGE_RESTART The computer must be restarted in order for the graphics mode to work.
DISP_CHANGE_BADFLAGS An invalid set of flags was passed in.
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_BADMODE The graphics mode is not supported.
DISP_CHANGE_NOTUPDATED Windows NT/2000: Unable to write settings to the registry.

Examples

Related Functions

 

 


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