Change Screen Resolution

Category:

System/API

Type:

Snippets

Difficulty:

Beginning

Author: Anantha PAdmanabhan

Version Compatibility: Visual Basic 6

More information:

To change screen resolution. Uses 2 API call. "EnumDisplaySettings" and "ChangeDisplaySettings". The effects can be surprising so use with care. It also affects all running (and minimised) programs. Origianl Credit:www.allapi.net.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
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 Dim OldXY As String Public aPossible

Code:

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 Command1_Click()
    Dim sMyData As String
    Dim iReply As Integer
    Dim aXY As Variant
    aXY = Array("", "")
    sMyData = aPossible(List1.ListIndex + 1)
    iReply = MsgBox("You have chosen:" + vbCrLf + sMyData, vbCritical + vbOKCancel)
    If iReply = vbOK Then
        aXY = Split(sMyData, "x")
        aXY(0) = CInt(aXY(0))
        aXY(1) = CInt(aXY(1))
'       ChangeRes aXY(0), aXY(1), GetDeviceCaps(nDC, BITSPIXEL)
    End If
End Sub

Private Sub Form_Load()
    'KPD-Team 1999
    'URL: http://www.allapi.net/
    'E-Mail: KPDTeam@Allapi.net
    Dim nDC As Long
    Dim sMyString As String
    Dim bReturn As Boolean
    Dim bFound As Boolean
    Dim lX As Long
    Dim iY As Integer       'resrved for the ordinal ubound of apossible
    Dim iz As Integer
    Dim DevM As DEVMODE
    sMyString = "The current list" + vbCrLf + vbCrLf
    sMyString = sMyString + "Screen Width:" + Str(Screen.Width) + vbCrLf
    sMyString = sMyString + "Screen Height:" + Str(Screen.Height) + vbCrLf
    sMyString = sMyString + "Screen TwipsPerPixelX:" + Str(Screen.TwipsPerPixelX) + vbCrLf
    sMyString = sMyString + "Screen TwipsPerPixelY:" + Str(Screen.TwipsPerPixelY) + vbCrLf
    
    'retrieve the screen's resolution
    OldX = Screen.Width / Screen.TwipsPerPixelX
    OldY = Screen.Height / Screen.TwipsPerPixelY
    sMyString = sMyString + "X resolution:" + Str(OldX) + vbCrLf
    sMyString = sMyString + "Y resolution:" + Str(OldY) + vbCrLf
'   MsgBox sMyString
'   Text2.Text = Trim$(Str(OldX))
'   Text3.Text = Trim$(Str(OldY))
    ReDim aPossible(1)
    aPossible(0) = Trim$(Str$(OldX)) + " x " + Trim$(Str$(OldY))
    Text4.Text = aPossible(0)
'   MsgBox aPossible(0)
    sMyString = ""
    lX = 0
    iY = 0
    'Create a device context, compatible with the screen
    nDC = CreateDC("DISPLAY", vbNullString, vbNullString, ByVal 0&)
    bReturn = True
    While bReturn
            bReturn = EnumDisplaySettings(0&, lX, DevM)
            If bReturn Then     'ie. a valid entry
'               sMyString = sMyString + Trim$(Str$(DevM.dmBitsPerPel)) + ":" + Trim$(Str$(DevM.dmPelsWidth)) + ":" + Trim$(Str$(DevM.dmPelsHeight)) + ":" + Str(lX) + vbCrLf
                sMyString = Trim$(Str$(DevM.dmPelsWidth)) + " x " + Trim$(Str$(DevM.dmPelsHeight))
                bFound = False
                For iz = 0 To iY
                    If sMyString = aPossible(iz) Then
                        bFound = True
                        Exit For
                    End If
                Next
                If Not bFound Then
                    iY = iY + 1
                    ReDim Preserve aPossible(iY)
                    aPossible(iY) = sMyString
                End If
                lX = lX + 1 'Dont forget this
            End If
    Wend
    sMyString = ""
    For iz = 1 To iY
        List1.AddItem aPossible(iz)
    Next
'   MsgBox sMyString
    'Change the screen's resolution
'   ChangeRes 640, 480, GetDeviceCaps(nDC, BITSPIXEL)
'    Unload Me
End Sub