Adjust the mouse speed when using Barrier (on Windows) to control another computer.

BarrierMouseSpeedFix.ps1

<#
.SYNOPSIS
Adjust the mouse speed when using Barrier (on Windows) to control another computer.

.DESCRIPTION
When using Barrier (https://github.com/debauchee/barrier) across two computers of different
resolutions/DPIs, the server's mouse speed may be too fast or too slow on the client computer:
https://github.com/debauchee/barrier/issues/741. This script monitors Barrier's log file and adjusts
the server's mouse speed when the mouse has moved onto the client.

Inspired in full by Aaron Jensen's (https://github.com/aaronjensen) script at
https://github.com/debauchee/barrier/issues/741#issuecomment-655317497.

.PARAMETER ClientMouseSpeed
The mouse speed to use when on the client computer. 1 is slowest, 20 is fastest

.PARAMETER LogFile
The path to the Barrier log file. Enable logging to file in the Barrier GUI under the
"Barrier" menu item > Change setting. Defaults to "C:\Program Files\Barrier\barrier.log"

.EXAMPLE
.\BarrierMouseSpeedFix.ps1 -ClientMouseSpeed 20
Move the mouse super fast when on the client.

.EXAMPLE
.\BarrierMouseSpeedFix.ps1 -ClientMouseSpeed 1 -LogFile "C:\tmp\barrier.log"
Move the mouse very slowly when on the client, provide a custom log file path.
#>

[CmdletBinding()]
param(
    [ValidateRange(1,20)]
    [int]$ClientMouseSpeed = 5,

    [string]$LogFile = "C:\Program Files\Barrier\barrier.log"
)

if (-not (Test-Path $LogFile -PathType Leaf)) {
    throw ("Log file not found at '{0}'" -f $LogFile)
}

$src = @"
    public const UInt32 SPI_GETMOUSESPEED = 0x0070;
    public const UInt32 SPI_SETMOUSESPEED = 0x0071;

    [DllImport("user32.dll", EntryPoint = "SystemParametersInfo")]
    public static extern bool SystemParametersInfoByRef(
        uint uiAction, uint uiParam,  ref uint pvParam, uint fWinIni);

    [DllImport("user32.dll", EntryPoint = "SystemParametersInfo")]
    public static extern bool SystemParametersInfoByVal(
        uint uiAction, uint uiParam,  uint pvParam, uint fWinIni);

    public static uint GetMouseSpeed()
    {
        uint speed = 0;
        SystemParametersInfoByRef(SPI_GETMOUSESPEED, 0, ref speed, 0);
        return speed;
    }

    public static bool SetMouseSpeed(uint speed)
    {
        return SystemParametersInfoByVal(SPI_SETMOUSESPEED, 0, speed, 0);
    }
"@

# If the type exists already (i.e. this script was run multiple times in the same PowerShell
# session), use it. Otherwise (i.e. this is the first time the script is run in the PowerShell
# session), define it to get access to the Win32 APIs.
try {
    $User32 = [Win32Functions.User32]
} catch {
    $User32 = Add-Type -MemberDefinition $src -Name "User32" -Namespace "Win32Functions" -PassThru
}

$originalMouseSpeed = $user32::GetMouseSpeed()

try {

    # Monitor the log file and adjust mouse speed when leaving and entering the server screen
    Get-Content $LogFile -Tail 1 -Wait | ForEach-Object {
        if ($_.EndsWith("leaving screen")) {
            $user32::SetMouseSpeed($ClientMouseSpeed) | Out-Null
        } elseif ($_.EndsWith("entering screen")) {
            $user32::SetMouseSpeed($originalMouseSpeed) | Out-Null
        }
    }

} catch {

    throw $_.Exception

} finally {

    # Reset to original mouse speed, in case anything weird happened
    $user32::SetMouseSpeed($originalMouseSpeed) | Out-Null
}