ChangeDisplaySettingsEx

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

This function changes the settings of the specified display device to the specified graphics mode.

Syntax

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

Parameters

• lpszDeviceName
  [in] Not used. Set to NULL.

• lpDevMode
  [in, out] Pointer to a DEVMODE structure that describes the new graphics mode.

  If lpDevMode is NULL, ChangeDisplaySettingsEx uses all of the values currently in the registry 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.

  You must initialize the dmSize member of the DEVMODE structure with the size, in bytes, of the structure. The following table shows the members of the DEVMODE structure that you can use.

  Value	Description
  dmDisplayOrientation	Screen rotation.

  Setting the dmBitsPerPel member is not supported.

  The following table shows the values in the dmFields member that you must also set to change the display settings, in addition to using one or more of the preceding DEVMODE members.

  Value	Description
  DM_DISPLAYQUERYORIENTATION	Check whether the display driver supports screen rotation. The supported screen orientations are returned in lpDevMode.dmDisplayOrientation. A value of just DMO_0 indicates that screen rotation is not supported.
  DM_DISPLAYORIENTATION	Use the dmDisplayOrientation value to change the orientation of the screen.

  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.

• hwnd
  [in] Reserved; must be NULL.

• dwflags
  [in] DWORD that indicates how you want to change the graphics mode. The following table shows the possible values.

  Value	Description
  0	Changes the graphics mode for the current screen dynamically.
  CDS_RESET	Changes the settings even if the requested settings are the same as the current settings.
  CDS_TEST	Tests if ChangeDisplaySettingsEx can set the requested graphics mode. Specifying CDS_TEST allows an application to determine which graphics modes are actually valid, without causing the system to change to the settings.
  CDS_VIDEOPARAMETERS	Indicates that the lParam parameter is a pointer to a VIDEOPARAMETERS structure.

• lParam
  [in] Pointer to a VIDEOPARAMETERS structure if dwFlags is CDS_VIDEOPARAMETERS. Otherwise, set to NULL.

Return Value

The following table shows the possible return values.

Remarks

When you change the display mode dynamically, the OS sends the WM_SETTINGCHANGE message to all running applications.

To query for the current orientation, call ChangeDisplaySettingsEx with lpDevMode set to DM_DISPLAYORIENTATION and dwflags set to CDS_TEST. The current orientation will be returned in lpDevMode.

The following table shows the value of the parameters that the OS uses when it sends this message.

Using the dmFields flag of DM_DISPLAYORIENTATION, ChangeDisplaySettingsEx can be used to dynamically rotate the screen orientation. For operating systems based on Windows CE 5.0 and earlier versions, the DM_PELSWIDTH and DM_PELSHEIGHT flags cannot be used to change the screen resolution.

Requirements

See Also

Reference

CreateDC
DEVMODE
EnumDisplaySettings