SystemParameter sInfo Failing in VB.net "Slide Open Combo Boxes"

[bpglen]

Could not figure out on how to reply to the last article with the same name. When I logged out it asked me to login and when I logged in there was no "post your reply" option, perhaps there is functional bug on this website, anyhow.

I had a similar problem where getting the value was okay but saving the value did not work, so I hope my solution helps, if someone else has a similar issue of understanding how to declare and use api functions.

[FYI: I was designing a user drawn combobox and the "Slide Open Combo Boxes" windows setting was effecting the display of the drop down portion of combo box. I got no text in the header portion and if my DataSource was only a few rows it showed no data at all and the height of the combo was only a few pixels !!?? My workaround was to toggle this windows setting value off then on again in the DropDown and DropDownClosed events respectively:

<DllImport("user32.dll", EntryPoint:="SystemParametersInfoA", SetLastError:=True, _
               CharSet:=CharSet.Ansi, ExactSpelling:=True, _
               CallingConvention:=CallingConvention.StdCall)> _
    Private Function SystemParametersInfoGet(ByVal uiAction As SPI_INDEX, ByVal uiParam As UInteger, _
                                          ByRef lpenabled As Boolean, ByVal fWinIni As UInteger) As Boolean
    End Function
    <DllImport("user32.dll", EntryPoint:="SystemParametersInfoA", SetLastError:=True, _
               CharSet:=CharSet.Ansi, ExactSpelling:=True, _
               CallingConvention:=CallingConvention.StdCall)> _
    Private Function SystemParametersInfoSet(ByVal uiAction As SPI_INDEX, ByVal uiParam As UInteger, _
                                          ByVal lpenabled As Boolean, ByVal fWinIni As UInteger) As Boolean
    End Function
 
    Public Function SlideOpenComboBoxes(ByVal TurnOn As Boolean) As Boolean
        Dim fResult As Boolean
        Dim spValue As UInteger
        Dim originalMaskOn As Boolean
 
        fResult = SystemParametersInfoGet(SPI_INDEX.SPI_GETCOMBOBOXANIMATION, 0, originalMaskOn, SPFIPersistance_INDEX.SPFI_NONE)
        Dim oWin32Ex As New Win32Exception()
        If fResult Then
            If TurnOn <> originalMaskOn Then
                fResult = SystemParametersInfoSet(SPI_INDEX.SPI_SETCOMBOBOXANIMATION, 0, TurnOn, SPFIPersistance_INDEX.SPFI_NONE)
                oWin32Ex = New Win32Exception()
            End If
        End If
        If Not fResult Then
            Throw oWin32Ex
        End If
        Return originalMaskOn
    End Function
End Module

I noticed 2 difference in the code snippets provided from the previous article compared to my solution above:

1. The first was the order of calling the parameters. I passed the variable I want to get or set into the call to the api as the third parameter. The previous article had Return = SystemParameter sInfo(SPI_SETSC REENSAVEACTIVE, lActiveFlag, 0, 0), so maybe the order is incorrect if I am not mistaken.
2. The other difference is I have two references to the api declaration, one for getting and the other for setting. The difference is use of ByVal (for setting) versus ByRef (for Getting) for the third parameter.

My solution was purely a trial an error effort I came to after googling and reading enough articles. I wish there was some documentation of the do's and dont's of API calling.

Without giving you my entire code base, if anyone else has experience owner drawing issues where this setting effected your code I would like to hear about your short comings and thus your work arounds and solutions to your issues.