Display's DPI Setting

[jamesa]

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.

[Shuja Ali]

Will this be of some help..

I found this on ALLAPI.NET

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

[jamesa]

thanks a lot,

I will try it.