Display's DPI Setting

Hallo,

I need please a help on, how to set, refresh or propagate Display's DPI Setting change?

for example, I want to change the display's DPI Setting from 96 to 120 without reboot.


Thanks a lot for your help.

Will this be of some help..

I found this on ALLAPI.NET

Code:

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Option Explicit
Const WM_DISPLAYCHANGE = &H7E
Const HWND_BROADCAST = &HFFFF&
Const EWX_LOGOFF = 0
Const EWX_SHUTDOWN = 1
Const EWX_REBOOT = 2
Const EWX_FORCE = 4
Const CCDEVICENAME = 32
Const CCFORMNAME = 32
Const DM_BITSPERPEL = &H40000
Const DM_PELSWIDTH = &H80000
Const DM_PELSHEIGHT = &H100000
Const CDS_UPDATEREGISTRY = &H1
Const CDS_TEST = &H4
Const DISP_CHANGE_SUCCESSFUL = 0
Const DISP_CHANGE_RESTART = 1
Const BITSPIXEL = 12
Private Type DEVMODE
        dmDeviceName As String * CCDEVICENAME
        dmSpecVersion As Integer
        dmDriverVersion As Integer
        dmSize As Integer
        dmDriverExtra As Integer
        dmFields As Long
        dmOrientation As Integer
        dmPaperSize As Integer
        dmPaperLength As Integer
        dmPaperWidth As Integer
        dmScale As Integer
        dmCopies As Integer
        dmDefaultSource As Integer
        dmPrintQuality As Integer
        dmColor As Integer
        dmDuplex As Integer
        dmYResolution As Integer
        dmTTOption As Integer
        dmCollate As Integer
        dmFormName As String * CCFORMNAME
        dmUnusedPadding As Integer
        dmBitsPerPel As Integer
        dmPelsWidth As Long
        dmPelsHeight As Long
        dmDisplayFlags As Long
        dmDisplayFrequency As Long
End Type
Private Declare Function EnumDisplaySettings Lib "user32" Alias "EnumDisplaySettingsA" (ByVal lpszDeviceName As Long, ByVal iModeNum As Long, lpDevMode As Any) As Boolean
Private Declare Function ChangeDisplaySettings Lib "user32" Alias "ChangeDisplaySettingsA" (lpDevMode As Any, ByVal dwFlags As Long) As Long
Private Declare Function ExitWindowsEx Lib "user32" (ByVal uFlags As Long, ByVal dwReserved As Long) As Long
Private Declare Function GetDeviceCaps Lib "gdi32" (ByVal hdc As Long, ByVal nIndex As Long) As Long
Private Declare Function CreateDC Lib "gdi32" Alias "CreateDCA" (ByVal lpDriverName As String, ByVal lpDeviceName As String, ByVal lpOutput As String, ByVal lpInitData As Any) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Dim OldX As Long, OldY As Long, nDC As Long
Sub ChangeRes(X As Long, Y As Long, Bits As Long)
        Dim DevM As DEVMODE, ScInfo As Long, erg As Long, an As VbMsgBoxResult
        'Get the info into DevM
        erg = EnumDisplaySettings(0&, 0&, DevM)
        'This is what we're going to change
        DevM.dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT Or DM_BITSPERPEL
        DevM.dmPelsWidth = X 'ScreenWidth
        DevM.dmPelsHeight = Y 'ScreenHeight
        DevM.dmBitsPerPel = Bits '(can be 8, 16, 24, 32 or even 4)
        'Now change the display and check if possible
        erg = ChangeDisplaySettings(DevM, CDS_TEST)
        'Check if succesfull
        Select Case erg&
                Case DISP_CHANGE_RESTART
                        an = MsgBox("You've to reboot", vbYesNo + vbSystemModal, "Info")
                        If an = vbYes Then
                                erg& = ExitWindowsEx(EWX_REBOOT, 0&)
                        End If
                Case DISP_CHANGE_SUCCESSFUL
                        erg = ChangeDisplaySettings(DevM, CDS_UPDATEREGISTRY)
                        ScInfo = Y * 2 ^ 16 + X
                        'Notify all the windows of the screen resolution change
                        SendMessage HWND_BROADCAST, WM_DISPLAYCHANGE, ByVal Bits, ByVal ScInfo
                        MsgBox "Everything's ok", vbOKOnly + vbSystemModal, "It worked!"
                Case Else
                        MsgBox "Mode not supported", vbOKOnly + vbSystemModal, "Error"
        End Select
End Sub
Private Sub Form_Load()
        'KPD-Team 1999
        'URL: http://www.allapi.net/
        'E-Mail: [email protected]
        Dim nDC As Long
        'retrieve the screen's resolution
        OldX = Screen.Width / Screen.TwipsPerPixelX
        OldY = Screen.Height / Screen.TwipsPerPixelY
        'Create a device context, compatible with the screen
        nDC = CreateDC("DISPLAY", vbNullString, vbNullString, ByVal 0&)
        'Change the screen's resolution
        ChangeRes 640, 480, GetDeviceCaps(nDC, BITSPIXEL)
End Sub
Private Sub Form_Unload(Cancel As Integer)
        'restore the screen resolution
        ChangeRes OldX, OldY, GetDeviceCaps(nDC, BITSPIXEL)
        'delete our device context
        DeleteDC nDC
End Sub

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thanks a lot,

I will try it.