How to check and modify display scale from VB.NET

Question

Hello, I would like to know if it were possible to check and modify the scale of a display via VB.NET code. I succeed in checking the resolution using the command: My.Computer.Screen.Bounds Is there something similar even for the scale factor? Thank you

Answer 1

To get it (one of the ways, there are others..) :

            Dim hMon As IntPtr = MonitorFromWindow(Me.Handle, MONITOR_DEFAULTTOPRIMARY)
            Dim dsf As DEVICE_SCALE_FACTOR
            GetScaleFactorForMonitor(hMon, dsf)
            MessageBox.Show(String.Format("Scale Factor : {0}", dsf.ToString()), "Information", MessageBoxButtons.OK, MessageBoxIcon.Information)

To change it : (nIndex depends on the default scale; for example on my PC, 0 = 100%, 1 = 125%, ...)

            Dim nIndex As Integer = 1
            SystemParametersInfo(SPI_SETLOGICALDPIOVERRIDE, nIndex, 0, SPIF_UPDATEINIFILE Or SPIF_SENDWININICHANGE)

With declarations :

    <DllImport("Shcore.dll", SetLastError:=True, CharSet:=CharSet.Unicode)>
    Public Shared Function GetScaleFactorForMonitor(hMon As IntPtr, ByRef pScale As DEVICE_SCALE_FACTOR) As HRESULT
    End Function

    Public Enum DEVICE_SCALE_FACTOR
        DEVICE_SCALE_FACTOR_INVALID = 0
        SCALE_100_PERCENT = 100
        SCALE_120_PERCENT = 120
        SCALE_125_PERCENT = 125
        SCALE_140_PERCENT = 140
        SCALE_150_PERCENT = 150
        SCALE_160_PERCENT = 160
        SCALE_175_PERCENT = 175
        SCALE_180_PERCENT = 180
        SCALE_200_PERCENT = 200
        SCALE_225_PERCENT = 225
        SCALE_250_PERCENT = 250
        SCALE_300_PERCENT = 300
        SCALE_350_PERCENT = 350
        SCALE_400_PERCENT = 400
        SCALE_450_PERCENT = 450
        SCALE_500_PERCENT = 500
    End Enum

    <DllImport("User32.dll", SetLastError:=True, CharSet:=CharSet.Unicode)>
    Public Shared Function MonitorFromWindow(ByVal hwnd As IntPtr, ByVal dwFlags As Integer) As IntPtr
    End Function

    <DllImport("User32.dll", SetLastError:=True, CharSet:=CharSet.Unicode)>
    Public Shared Function SystemParametersInfo(uiAction As UInteger, uiParam As Integer, ByRef pvParam As Integer, fWinIni As UInteger) As Boolean
    End Function

    Public Const SPIF_UPDATEINIFILE As Integer = &H1
    Public Const SPIF_SENDWININICHANGE As Integer = &H2

    Public Const MONITOR_DEFAULTTONULL As Integer = &H0
    Public Const MONITOR_DEFAULTTOPRIMARY As Integer = &H1
    Public Const MONITOR_DEFAULTTONEAREST As Integer = &H2

    Public Const SPI_GETLOGICALDPIOVERRIDE = &H9E
    Public Const SPI_SETLOGICALDPIOVERRIDE = &H9F

Answer 2

Hello, First of all, thank you for your answer. I made a test with your code and I succeed in changing the monitor scaling factor. Unfortunately, I did not succeed in viewing the current scaling factor: the message reports 100% when it was set to 100% (so in this case was correct), but when I tried to set other scaling factor (125, 150 and 175%) both from script and manually, the result was always "SCALE__140__PERCENT" I don't understand how the function "GetScaleFactorForMonitor" works, since there are no instruction before the End function