dotnet/wpf · error · Win32Exception

Win32Exception (native SystemParametersInfo failure…

Error message

Win32Exception (native SystemParametersInfo failure retrieving MouseVanish)

What it means

The MouseVanish property calls SystemParametersInfo(SPI_GETMOUSEVANISH); if it returns false, the cache slot is cleared and a Win32Exception is thrown. It indicates the OS could not report whether the pointer hides while typing. Thrown from the public getter on the first, uncached read.

Solutions

Retry the property; the cache slot was invalidated so a subsequent read re-issues the SPI call.
Wrap in try/catch(Win32Exception) and default to false (pointer not vanishing).
Test on a physical, interactive session; treat remote-session environments as the likely culprit.
If supporting remotes is required, pre-check the session type (SystemInformation.TerminalServerSession) and skip the read.

Example fix

// before
bool vanish = SystemParameters.MouseVanish;
// after
bool vanish = SystemInformation.TerminalServerSession
    ? false
    : ReadMouseVanishWithFallback(); // try/catch(Win32Exception) => false

Defensive patterns

Strategy: fallback

Validate before calling

bool sessionOk = !SystemInformation.TerminalServerSession && Environment.UserInteractive;
// SPI_GETMOUSEVANISH is commonly unsupported in remote sessions; skip when sessionOk is false

Try / catch

bool vanish;
try { vanish = SystemParameters.MouseVanish; }
catch (Win32Exception)
{
    vanish = false; // safe default: pointer does not vanish
}

Prevention

Pre-check SystemInformation.TerminalServerSession before reading MouseVanish
Provide a hard default rather than crashing on unsupported SPI queries
Retry once; the cache slot invalidation enables a fresh query
Log the environment (session type, OS) when this fires

When it happens

Trigger: First access of SystemParameters.MouseVanish in an environment where SPI_GETMOUSEVANISH fails - notably Terminal Services/remote sessions where the parameter is unsupported, or pointer settings unreadable.

Common situations: RDP/Citrix sessions lacking mouse-vanish support; automation harnesses running headless; older or stripped-down Windows editions.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/083898667500037e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/SystemParameters.cs:208

        /// </summary>
        // If this becomes public, it will need a matching ResourceKey.
        internal static bool MouseVanish
        {
            get
            {
                lock (_cacheValid)
                {
                    while (!_cacheValid[(int)CacheSlot.MouseVanish])
                    {
                        _cacheValid[(int)CacheSlot.MouseVanish] = true;

                        if (UnsafeNativeMethods.SystemParametersInfo(NativeMethods.SPI_GETMOUSEVANISH, 0, ref _mouseVanish, 0))
                        {
                        }
                        else
                        {
                            _cacheValid[(int)CacheSlot.MouseVanish] = false;
                            throw new Win32Exception();
                        }
                    }
                }

                return _mouseVanish;
            }
        }

        #endregion

        [System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.NoInlining)]
        private static SystemResourceKey CreateInstance(SystemResourceKeyID KeyId)
        {
            return new SystemResourceKey(KeyId);
        }

        #region Accessibility Keys

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