DllCall Newbie - What is the return type for ChangeDisplaySettingsEx function?

[TheDcoder]

Hello! I am pretty new to DLL stuff and I have spent a lot of hours on crafting a DLL call for the ChangeDisplaySettingsEx function. I tried my code and DllCall reports success, that is good . But I am not able to identify the "return type" parameter that I should use for DllCall. I tried STR which returned an empty string, I also tried INT which returned 0... According to Microsoft's documentation, the function should return of these:

Quote

Return value

The ChangeDisplaySettingsEx function returns one of the following values.

Return code	Description
DISP_CHANGE_SUCCESSFUL	The settings change was successful.
DISP_CHANGE_BADDUALVIEW	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	Unable to write settings to the registry.
DISP_CHANGE_RESTART	The computer must be restarted for the graphics mode to work.

Can anyone help me out here? They all look like constants to me and I cannot find their values .

Thanks in Advance! TD

[kosamja]

from here:

http://www.math.uiuc.edu/~gfrancis/illimath/windows/aszgard_mini/bin/MinGW/include/winuser.h

#define DISP_CHANGE_SUCCESSFUL  0
#define DISP_CHANGE_RESTART 1
#define DISP_CHANGE_BADFLAGS    (-4)
#define DISP_CHANGE_BADPARAM    (-5)
#define DISP_CHANGE_FAILED  (-1)
#define DISP_CHANGE_BADMODE (-2)
#define DISP_CHANGE_NOTUPDATED  (-3)

 

Edited August 14, 2017 by kosamja

[Danyfirex]

Hello. Return type is Long.

LONG ChangeDisplaySettingsEx(
  _In_ LPCTSTR lpszDeviceName,
  _In_ DEVMODE *lpDevMode,
       HWND    hwnd,
  _In_ DWORD   dwflags,
  _In_ LPVOID  lParam
);

 

 

Saludos

[TheDcoder]

Thanks both of you!