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Tip of the Day
Language: VB4/32,VB5,VB6
Expertise: Intermediate
Jan 20, 2001



Building the Right Environment to Support AI, Machine Learning and Deep Learning

ChangeScreenResolution - Change the current screen resolution

Option Explicit

Const DM_BITSPERPEL As Long = &H40000
Const DM_PELSWIDTH As Long = &H80000
Const DM_PELSHEIGHT As Long = &H100000
Const CDS_FORCE As Long = &H80000000

Const CCDEVICENAME As Long = 32
Const CCFORMNAME As Long = 32

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 Long
    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 modeIndex As Long, lpDevMode As Any) As Boolean
Private Declare Function ChangeDisplaySettings Lib "user32" Alias _
    "ChangeDisplaySettingsA" (lpDevMode As Any, ByVal dwflags As Long) As Long

' change the screen resolution mode
' returns True if the requested resolution mode is among those
' supported by the display adapter (otherwise it doesn't even
' try to change the screen resolution)

Function ChangeScreenResolution(ByVal Width As Long, ByVal Height As Long, _
    ByVal NumColors As Long, Optional Frequency As Long) As Boolean
    Dim lpDevMode As DEVMODE
    Dim index As Long
    ' set the DEVMODE flags and structure size
    lpDevMode.dmSize = Len(lpDevMode)
    ' retrieve info on the Nth display mode, exit if no more
    Do While EnumDisplaySettings(0, index, lpDevMode) > 0
        ' check whether this is the mode we're looking for
        If lpDevMode.dmPelsWidth = Width And lpDevMode.dmPelsHeight = Height _
            And 2 ^ lpDevMode.dmBitsPerPel = NumColors Then
            ' check that the frequency is also the one we're looking for
            If Frequency = 0 Or Frequency = lpDevMode.dmDisplayFrequency Then
                ' try changing the resolution
                If ChangeDisplaySettings(lpDevMode, CDS_FORCE) = 0 Then
                    ' zero means success
                    ChangeScreenResolution = True
                    Exit Do
                End If
            End If
        End If
        ' skip to next screen mode
        index = index + 1

End Function

Francesco Balena
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