Exception on \text{∅}

[ForNeVeR]

Whenever I enter a text \text{∅}, the parser throws an exception:

Unhandled exception. System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
   at MS.Internal.FontCache.FontFaceLayoutInfo.IntMap.System.Collections.Generic.IDictionary<System.Int32,System.UInt16>.get_Item(Int32 i)
   at WpfMath.Boxes.CharBox.GetGlyphRun(Double scale, Double x, Double y) in D:\X-Files\Projects\wpf-math\src\WpfMath\Boxes\CharBox.cs:line 29
   at WpfMath.Boxes.CharBox.<>c__DisplayClass6_0.<RenderTo>b__0(Double scale) in D:\X-Files\Projects\wpf-math\src\WpfMath\Boxes\CharBox.cs:line 39
   at WpfMath.Rendering.WpfElementRenderer.RenderGlyphRun(Func`2 scaledGlyphFactory, Double x, Double y, Brush foreground) in D:\X-Files\Projects\wpf-math\src\WpfMath\Re
ndering\WpfElementRenderer.cs:line 47
   at WpfMath.Boxes.CharBox.RenderTo(IElementRenderer renderer, Double x, Double y) in D:\X-Files\Projects\wpf-math\src\WpfMath\Boxes\CharBox.cs:line 39
   at WpfMath.Rendering.WpfElementRenderer.RenderElement(Box box, Double x, Double y) in D:\X-Files\Projects\wpf-math\src\WpfMath\Rendering\WpfElementRenderer.cs:line 39

   at WpfMath.TexRenderer.RenderFormulaTo(IElementRenderer renderer, Double x, Double y) in D:\X-Files\Projects\wpf-math\src\WpfMath\TexRenderer.cs:line 51
   at WpfMath.TexRenderer.Render(DrawingContext drawingContext, Double x, Double y) in D:\X-Files\Projects\wpf-math\src\WpfMath\TexRenderer.cs:line 96
   at WpfMath.Controls.FormulaControl.Render() in D:\X-Files\Projects\wpf-math\src\WpfMath\Controls\FormulaControl.xaml.cs:line 157
   at WpfMath.Controls.FormulaControl.OnRenderSettingsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) in D:\X-Files\Projects\wpf-math\src\WpfMath\Contr
ols\FormulaControl.xaml.cs:line 191
   at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
   at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, Effecti
veValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp, Boolean preserveCurrentValue)
   at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp)
   at System.Windows.Data.BindingExpressionBase.Invalidate(Boolean isASubPropertyChange)
   at System.Windows.Data.BindingExpression.TransferValue(Object newValue, Boolean isASubPropertyChange)
   at System.Windows.Data.BindingExpression.ScheduleTransfer(Boolean isASubPropertyChange)
   at MS.Internal.Data.ClrBindingWorker.NewValueAvailable(Boolean dependencySourcesChanged, Boolean initialValue, Boolean isASubPropertyChange)
   at MS.Internal.Data.PropertyPathWorker.UpdateSourceValueState(Int32 k, ICollectionView collectionView, Object newValue, Boolean isASubPropertyChange)
   at MS.Internal.Data.PropertyPathWorker.OnDependencyPropertyChanged(DependencyObject d, DependencyProperty dp, Boolean isASubPropertyChange)
   at MS.Internal.Data.ClrBindingWorker.OnSourceInvalidation(DependencyObject d, DependencyProperty dp, Boolean isASubPropertyChange)
   at System.Windows.Data.BindingExpression.HandlePropertyInvalidation(DependencyObject d, DependencyPropertyChangedEventArgs args)
   at System.Windows.Data.BindingExpressionBase.OnPropertyInvalidation(DependencyObject d, DependencyPropertyChangedEventArgs args)
   at System.Windows.Data.BindingExpression.OnPropertyInvalidation(DependencyObject d, DependencyPropertyChangedEventArgs args)
   at System.Windows.DependentList.InvalidateDependents(DependencyObject source, DependencyPropertyChangedEventArgs sourceArgs)
   at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
   at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, Effecti
veValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, Boolean coerceW
ithCurrentValue, OperationType operationType, Boolean isInternal)
   at System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value)
   at System.Windows.Controls.TextBox.set_Text(String value)
   at WpfMath.Example.MainWindow.Window_Loaded(Object sender, RoutedEventArgs e) in D:\X-Files\Projects\wpf-math\src\WpfMath.Example\MainWindow.xaml.cs:line 111
   at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
   at System.Windows.BroadcastEventHelper.BroadcastEvent(DependencyObject root, RoutedEvent routedEvent)
   at System.Windows.BroadcastEventHelper.BroadcastLoadedEvent(Object root)
   at MS.Internal.LoadedOrUnloadedOperation.DoWork()
   at System.Windows.Media.MediaContext.FireLoadedPendingCallbacks()
   at System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks()
   at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget)
   at System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget)
   at System.Windows.Media.MediaContext.Resize(ICompositionTarget resizedCompositionTarget)
   at System.Windows.Interop.HwndTarget.OnResize()
   at System.Windows.Interop.HwndTarget.HandleMessage(WindowMessage msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Interop.HwndSource.HwndTargetFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)

[rstm-sf]

Arial does not support diameter sign. For this we need to choose one supported wpf: DIAMETER SIGN (U+2300) Font Support

https://github.com/ForNeVeR/wpf-math/blob/1efa09e3d3b2f74d5d5fcfb2a847410f6bacaaf1/src/WpfMath/Controls/FormulaControl.xaml.cs#L82-L84

[ForNeVeR]

It still sholdn't throw an exception no matter what :)