Setting Primary Display

Jayme65

Hi, I'm trying to set the Primary Display...without success! Here's the code I'm working on, would you please help me see what I'm doing wrong there? There's no compilation error...it simply doesn't give the expected result! Thank you!!

Imports System.Runtime.InteropServices
Class MainWindow
Const CCDEVICENAME As Short = 32
Const CCFORMNAME As Short = 32

Private Const MONITORINFOF\_PRIMARY As Integer = &H1
Private Const DISPLAY\_DEVICE\_ATTACHED\_TO\_DESKTOP As Integer = &H1
Private Const DISPLAY\_DEVICE\_PRIMARY\_DEVICE As Integer = &H4
Private Const DISPLAY\_DEVICE\_MIRRORING\_DRIVER As Integer = &H8
Private Const DISPLAY\_DEVICE\_VGA\_COMPATIBLE As Integer = &H10
Private Const DISPLAY\_DEVICE\_REMOVABLE As Integer = &H20
Private Const DISPLAY\_DEVICE\_MODESPRUNED As Integer = &H8000000

Private Const DM\_POSITION = &H20
Private Const DM\_DISPLAYORIENTATION = &H80 ' XP only
Private Const DM\_BITSPERPEL = &H40000
Private Const DM\_PELSWIDTH = &H80000
Private Const DM\_PELSHEIGHT = &H100000
Private Const DM\_DISPLAYFLAGS = &H200000
Private Const DM\_DISPLAYFREQUENCY = &H400000
'Private Const DM\_DISPLAYFIXEDOUTPUT As Long = &H20000000 ' XP only

Private Const ENUM\_CURRENT\_SETTINGS As Integer = -1
Private Const ENUM\_REGISTRY\_SETTINGS As Integer = -2
Private Const EDS\_RAWMODE As Integer = &H2

Private Const CDS\_UPDATEREGISTRY As Integer = &H1
Private Const CDS\_TEST As Integer = &H2
Private Const CDS\_FULLSCREEN As Integer = &H4
Private Const CDS\_GLOBAL As Integer = &H8
Private Const CDS\_SET\_PRIMARY As Integer = &H10
Private Const CDS\_VIDEOPARAMETERS As Integer = &H20
Private Const CDS\_NORESET As Integer = &H10000000
Private Const CDS\_RESET As Integer = &H40000000
Private Const CDS\_FORCE As Integer = &H80000000
Private Const CDS\_NONE As Integer = 0

Public Structure PointL
    Dim x As Integer
    Dim y As Integer
End Structure

\_
Enum DisplayDeviceStateFlags As Integer
    AttachedToDesktop = &H1
    MultiDriver = &H2
    PrimaryDevice = &H4
    MirroringDriver = &H8
    VGACompatible = &H10
    Removable = &H20
    ModesPruned = &H8000000
    Remote = &H4000000
    Disconnect = &H2000000
End Enum

'0 is Not Attached

Const DISPLAY\_PRIMARY\_DEVICE = &H4 'Primary device

'Holds the information of display adpter
Private Structure DISPLAY\_DEVICE

Richard Andrew x64

Well did you step through it in the debugger and check the return values from the functions that do the work? You need to narrow it down to exactly which function call is not working as intended.

The difficult we do right away... ...the impossible takes slightly longer.

Jayme65

It returns a 0 (DISP_CHANGE_SUCCESSFUL) !!

Richard Andrew x64

Did you study the documentation? ChangeDisplaySettingsEx function (Windows)[^]

The difficult we do right away... ...the impossible takes slightly longer.