Set-TouchPadScrollDirection.ps1

[CmdletBinding(SupportsShouldProcess)]
param(
    [Parameter(Position = 0)]
    [ValidateSet("Up", "Down")]
    [string]$ScrollDirection = "Down",
    [Parameter(Position = 1)]
    [switch]$ForAllNewProfiles
)

begin {

    #The registry key path and property that controls which direction touchpad scrolling operates.
    switch ($ForAllNewProfiles) {
        $true {
            $touchpadScrollReg = [pscustomobject]@{
                "RegPath" = "HKLM:\DefaultProfile\SOFTWARE\Microsoft\Windows\CurrentVersion\PrecisionTouchPad";
                "Name"    = "ScrollDirection";
                "Type"    = "DWORD";
            }
            break
        }

        Default {
            $touchpadScrollReg = [pscustomobject]@{
                "RegPath" = "HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\PrecisionTouchPad";
                "Name"    = "ScrollDirection";
                "Type"    = "DWORD";
            }
            break
        }
    }

    #Defining the two values for the direction
    $scrollOptions = @(
        [pscustomobject]@{
            "ScrollDownDirection" = "Up";
            "Value"               = 0x0;
        },
        [pscustomobject]@{
            "ScrollDownDirection" = "Down";
            "Value"               = 0xffffffff;
        }
    )
}

process {
    $selectedOption = $null
    switch ($ScrollDirection) {
        "Up" {
            #If the scroll direction is set to "Up"
            Write-Verbose "Selected option is to scroll up."
            $selectedOption = $scrollOptions | Where-Object { $PSItem.ScrollDownDirection -eq "Up" }
            break
        }

        Default {
            #If the scroll direction is set to "Down"
            Write-Verbose "Selected option is to scroll down."
            $selectedOption = $scrollOptions | Where-Object { $PSItem.ScrollDownDirection -eq "Down" }
            break
        }
    }

    #Creating a splat that can be used by both 'New-ItemProperty' and 'Set-ItemProperty'.
    $itemPropertySplat = @{
        "Path"        = $touchpadScrollReg.RegPath;
        "Name"        = $touchpadScrollReg.Name;
        "Value"       = $selectedOption.Value;
        "ErrorAction" = "Stop";
    }

    switch ($ForAllNewProfiles) {
        $true {
            #If the script is running to modify the default profile's registry hive
            Write-Warning "Setting the option in the default profile's registry hive."

            if ($PSCmdlet.ShouldProcess("Default Profile", "Load registry hive")) {
                #Create a temporary file to redirect the output of the 'reg' command
                $tmpFile = New-TemporaryFile

                #Get the file path for the default profile's registry hive.
                $defaultRegHivePath = "$($env:SystemDrive)\Users\Default\NTUSER.DAT"

                #Load the default profile's registry hive
                Start-Process -FilePath "reg" -ArgumentList @("load", "HKLM\DefaultProfile", "$($defaultRegHivePath)") -Wait -NoNewWindow -RedirectStandardOutput $tmpFile.FullName
            }

            break
        }

        Default {
            #Else, do nothing
            break
        }
    }

    #Change the scroll direction
    if ($PSCmdlet.ShouldProcess("Scroll direction", "Change scroll direction to $($selectedOption.ScrollDownDirection.ToLower())")) {
        try {
            $null = New-ItemProperty @itemPropertySplat -PropertyType $touchpadScrollReg.Type
        }
        catch [System.IO.IOException] {
            #If the property already exists, then just set it.
            $null = Set-ItemProperty @itemPropertySplat
        }
    }

    switch ($ForAllNewProfiles) {
        $true {
            #If the script is running to modify the default profile's registry hive

            if ($PSCmdlet.ShouldProcess("Default Profile", "Unload registry hive")) {
                #In order to successfully unload the loaded registry hive, we need to do garbage collection
                [System.GC]::Collect()

                #Unload the registry hive
                Start-Process -FilePath "reg" -ArgumentList @("unload", "HKLM\DefaultProfile") -Wait -NoNewWindow -RedirectStandardOutput $tmpFile.FullName

                #Remove the temp file
                $tmpFile | Remove-Item -Force
            }

            Write-Warning "Changes will not have an effect on users who have already logged in. This will only apply to new users who log into this computer."
            break
        }

        Default { #Else, show the warning about when the setting will take effect
            Write-Warning "In order for changes to take effect, you must log out and then log back in."
            break
        }
    }
}