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API: Detect Available Resolutions

Dev Ashish

(Q)    How can I detect the various supported resolutions and change to one of the settings at runtime?

(A) The following functions can be used to enumerate the various display settings and change the screen resolution at runtime.

Note:  This code is not meant to be a replacement for rescaling the forms to match the display resolution at runtime.   Changing the client's Control Panel settings is not user friendly behavior and is generally  NOT recommended.

'****************** Code Start *****************
' This code was originally written by Dev Ashish.
' It is not to be altered or distributed,
' except as part of an application.
' You are free to use it in any application,
' provided the copyright notice is left unchanged.
' Code Courtesy of
' Dev Ashish
Private Const CCDEVICENAME = 32
Private Const CCFORMNAME = 32
Private Const DM_PELSWIDTH = &H80000
Private Const DM_PELSHEIGHT = &H100000

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 apiEnumDisplaySettings Lib "user32" _
        Alias "EnumDisplaySettingsA" _
        (ByVal lpszDeviceName As Long, _
        ByVal iModeNum As Long, _
        lpDevMode As Any) _
        As Boolean

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

Function fEnumDisplay() As Collection
Dim collRes As Collection
Dim boolRet As Boolean
Dim tDevMode As DEVMODE
Dim lngMode As Long

    Set collRes = New Collection
        boolRet = apiEnumDisplaySettings(0&, lngMode&, tDevMode)
        With tDevMode
            collRes.Add .dmPelsWidth & "x" & _
                    .dmPelsHeight & " @ " & .dmBitsPerPel & " bit", _
                    lngMode & vbNullString
        End With
        lngMode = lngMode + 1
    Loop Until boolRet = False
    Set fEnumDisplay = collRes
    Set collRes = Nothing
End Function

Function fChangeRes(intX As Integer, intY As Integer) As Boolean
Dim tDevMode As DEVMODE
Dim boolCanChange As Boolean
Dim boolRet As Boolean
Dim lngRet As Long, lngMode As Long

    On Error GoTo Err_Handler
        boolRet = apiEnumDisplaySettings(0&, lngMode&, tDevMode)
        With tDevMode
            If .dmPelsWidth = intX And .dmPelsHeight = intY Then
                boolCanChange = True
            End If
        End With
        lngMode = lngMode + 1
    Loop Until boolRet = False

    If boolCanChange Then
        With tDevMode
            .dmFields = DM_PELSWIDTH Or DM_PELSHEIGHT
            .dmPelsWidth = intX
            .dmPelsHeight = intY
        End With
        lngRet = apiChangeDisplaySettings(tDevMode, 0&)
    End If
    fChangeRes = boolCanChange
    Exit Function
    fChangeRes = False
    Resume exit_Handler
End Function
'****************** Code End *****************

1998-2009, Dev Ashish & Arvin Meyer, All rights reserved. Optimized for Microsoft Internet Explorer