dotnet/wpf · error · InvalidOperationException

SR.PenService_WindowNotRegistered

Error message

SR.PenService_WindowNotRegistered

What it means

WispLogic (WispLogic.cs:3226) throws InvalidOperationException(SR.PenService_WindowNotRegistered) when a lookup for the PenContexts of a given PresentationSource returns null — i.e. the window was never registered with the pen service (or was already unregistered). The stylus stack cannot route tablet input for an unregistered window.

Solutions

  1. Register the window's PresentationSource with the stylus service before any PenContexts-dependent call.
  2. Check the window/source is still open and registered before issuing stylus commands.
  3. Ensure unregistration on close does not run earlier than subsequent stylus calls in your shutdown sequence.

Example fix

// before
void OnClose(object s, EventArgs e) { DisableStylus(window); window.Close(); Unregister(window); }
// after
void OnClose(object s, EventArgs e) { window.Close(); Unregister(window); } // unregister last
Defensive patterns

Strategy: validation

Validate before calling

if (window == null || !window.IsLoaded) return; // window must be open and registered before stylus calls

Try / catch

try { EnableStylusForWindow(window); } catch (InvalidOperationException ex) when (ex.Message.Contains("not registered")) { /* register the source first, then retry once */ }

Prevention

When it happens

Trigger: Calling WispLogic APIs that resolve PenContexts for an input source (e.g. enabling/disabling stylus for a window, toggling RealTimeStylus paths) before RegisterStylusPointProcessor/source registration, or after the source was unregistered on close.

Common situations: Calling stylus enable/disable APIs in a window constructor before the HwndSource exists; operating on a closed window; mismatched ordering between plugin registration and use across app lifetime events.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/016f7789f7973b1a. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Stylus/Wisp/WispLogic.cs:3226

                if (__penContextsMap.TryGetValue(hwndSource, out penContexts))
                {
                    __penContextsMap.Remove(hwndSource);

                    // 
                    // If the application dispatcher is being shut down, we should destroy our pen thread as well.
                    penContexts.Disable(shutdownWorkThread);

                    // Make sure we remember the last location of this window for mapping stylus input later.
                    if (UnsafeNativeMethods.IsWindow(new HandleRef(hwndSource, hwndSource.Handle)))
                    {
                        penContexts.DestroyedLocation = PointUtil.ClientToScreen(new Point(0, 0), hwndSource);
                    }
                }

                // If we failed to find penContexts for this window above then throw an error now.
                if (penContexts == null)
                {
                    throw new InvalidOperationException(SR.PenService_WindowNotRegistered);
                }
            }
        }


        /////////////////////////////////////////////////////////////////////

        internal PenContexts GetPenContextsFromHwnd(PresentationSource presentationSource)
        {
            // Only safe to call from UI thread since only it will change Map.
            Debug.Assert(Dispatcher.CheckAccess());

            PenContexts penContexts = null;

            if (presentationSource != null)
            {
                __penContextsMap.TryGetValue(presentationSource, out penContexts);
            }

View on GitHub (pinned to 81131a70a4)