Improve error handling by displaying an error message (#1075)

* wire up error messages

* more errors

* fix crash on render error

* Always show copy and cut

* PR comments

* Fix spelling

src/GraphControl/Models/Equation.h

@@ -7,6 +7,200 @@
 
 namespace GraphControl
 {
+    public enum class ErrorType
+    {
+        Evaluation,
+        Syntax,
+        Abort,
+    };
+
+    public enum class EvaluationErrorCode
+    {
+        // Number is too large. To see this error, assign a large number to variable a, then keep doing "a:=a*a" until it happens
+        Overflow = 2,
+
+        // doing trig in calculus and current mode is not Radians
+        RequireRadiansMode = 3,
+
+        // This is actually abort code generated as time limit reached.
+        TooComplexToSolve = 4,
+
+        // degree sign present and the current mode is not Degrees
+        RequireDegreesMode = 5,
+
+        // n! and n is not an non-negative integer or m/2
+        FactorialInvalidArgument = -1,
+
+        // n!! and n is not an non-negative integer or odd negative integers
+        Factorial2InvalidArgument = -2,
+
+        // n! and n is too big
+        FactorialCannotPerformOnLargeNumber = -3,
+
+        // x mod y, and one of them is not an integer
+        ModuloCannotPerformOnFloat = -5,
+
+        // below are equation solving specific errors
+
+        // example1: sin(x)+x=2    example2: x^4-x^3-8x=9
+        EquationTooComplexToSolveSymbolic = -7,
+
+        // example1: x-x=3    example2: x^2=-1
+        EquationHasNoSolution = -8,
+
+        // only used for numeric solve where the algorithm doesn't converge
+        EquationTooComplexToSolve = -9,
+
+        // used when equation cannot be ploted
+        EquationTooComplexToPlot = -10,
+
+        // example1: 1/0
+        DivideByZero = -15,
+
+        // the inequality is too complex for the engine to solve
+        InequalityTooComplexToSolve = -41,
+
+        // the inequality has no solution
+        InequalityHasNoSolution = -42,
+
+        // An exression contains logical conditions that are mutually exclusive
+        MutuallyExclusiveConditions = -43,
+
+        // Arbitrary Precision Evaluation input is out of domain
+        OutOfDomain = -101,
+
+        // Not supported.
+        GE_NotSupported = -503,
+
+        // General error for graphing engine
+        GE_GeneralError = -504,
+
+        // Failed to calculate
+        GE_TooComplexToSolve = -506,
+    };
+
+    public enum class SyntaxErrorCode
+    {
+        // found ) without matching (
+        ParenthesisMismatch = 1,
+
+        // found ( without matching )
+        UnmatchedParenthesis = 2,
+
+        // more than 1 decimal point in a number. Example: 7.3.2
+        TooManyDecimalPoints = 3,
+
+        // decimal point on its own without any digits surrounding it. Example: 3+.+4
+        DecimalPointWithoutDigits = 4,
+
+        // example: 3-4*
+        UnexpectedEndOfExpression = 5,
+
+        // example: 3-*4
+        UnexpectedToken = 6,
+
+        // example: [    (or many other special characters), another example: "3,5" (comma is invalid here)
+        InvalidToken = 7,
+
+        // example: solve(x+3=8=x)
+        TooManyEquals = 8,
+
+        // example: ploteq(4+83=9)
+        EqualWithoutGraphVariable = 10,
+
+        // <para>example: ploteq(x+y)        (expecting "=" in equation ploting)</para>
+        // <para>example2: Solve(5*x+9)    (expecting = in the equation solving)</para>
+        InvalidEquationSyntax = 11,
+
+        // there is nothing in the expression
+        EmptyExpression = 12,
+
+        // example: factor(x=3) (expecting solve(x=3)).
+        EqualWithoutEquation = 14,
+
+        // example: solve( (x=3)*2 )
+        InvalidEquationFormat = 15,
+
+        // This error only occurs when CasContext.ParsingOptions.AllowImplicitParentheses == false.
+        // example: sin a    (expecting sin(a))
+        ExpectParenthesisAfterFunctionName = 25,
+
+        // example: root(a)    (expecting 2 parameters)
+        IncorrectNumParameter = 26,
+
+        // exmaple: "x_", "x_@", "x__1"
+        InvalidVariableNameFormat = 32,
+
+        // found } without matching {
+        BracketMismatch = 34,
+
+        // found { without matching }
+        UnmatchedBracket = 35,
+
+        // syntax error in MathML format. Used only if CasContext.ParsingOptions.FormatType is MathML or MathMLNoWrapper
+        InvalidMathMLFormat = 40,
+
+        // The input has an unknown MathML entity. Used only if CasContext.ParsingOptions.FormatType is MathML or MathMLNoWrapper
+        UnknownMathMLEntity = 41,
+
+        // The input has an unknown MathML element. Used only if CasContext.ParsingOptions.FormatType is MathML or MathMLNoWrapper
+        UnknownMathMLElement = 42,
+
+        // "i" and "I" cannot be used as variable names in real number field
+        CannotUseIInReal = 48,
+
+        // General error
+        GeneralError = 52,
+
+        // used in parsing numbers with arbitrary bases. example: base(2, 1020), base(16, 1AG)
+        InvalidNumberDigit = 55,
+
+        // a valid number base must be an integer >=2 and &lt;=36
+        InvalidNumberBase = 56,
+
+        // some functions require a variable in certain argument position. e.g. 2nd argument of deriv, integral, limit, etc.
+        // this error code is used if the argument at the position is not a variable
+        InvalidVariableSpecification = 57,
+
+        // all operands of logical operators must be logical. example: "true and 1"
+        ExpectingLogicalOperands = 58,
+
+        // all operands of a non-logical operator must not be logical. example: "sin(true)"
+        ExpectingScalarOperands = 59,
+
+        // a list can contain logicals or scalars, but not both.
+        CannotMixLogicalScalarInList = 60,
+
+        // in definite integral, seriesSum and seriesProduct, the index variable is used in the lower/upper limits.
+        // example: integral(sin(x), x, 0, x)
+        CannotUseIndexVarInOpLimits = 61,
+
+        // in limit, the index variable is used in the limit point
+        // example: limit(sin(x), x, x-1)
+        CannotUseIndexVarInLimPoint = 62,
+
+        /// ComplexInfinity cannot be used in real number field
+        CannotUseComplexInfinityInReal = 72,
+
+        // complex numbers are not allowed in inequality solving
+        CannotUseIInInequalitySolving = 123,
+
+        // Indicate a bug in the MathRichEdit serializer
+        RichEditSerializationError = 201,
+
+        // can't initialize math zone in richedit, meaning it's the wrong version richedit dll, need reinstall
+        RichEditInitialization = 202,
+
+        // indicate bug in either richedit or richedit wrapper
+        RichEditInlineObjectStructure = 203,
+
+        // in a structure like integral, sum, product, one of the boxes is not filled
+        RichEditMissingArgument = 204,
+
+        // errors in richedit wrapper that are not specifically handled for
+        RichEditGeneralError = 210,
+    };
+
     [Windows::UI::Xaml::Data::Bindable] public ref class Equation sealed : public Windows::UI::Xaml::Data::INotifyPropertyChanged
     {
     public:
@@ -18,6 +212,8 @@ namespace GraphControl
         OBSERVABLE_NAMED_PROPERTY_RW(bool, IsValidated);
         OBSERVABLE_NAMED_PROPERTY_RW(bool, HasGraphError);
         OBSERVABLE_NAMED_PROPERTY_RW(bool, IsSelected);
+        OBSERVABLE_NAMED_PROPERTY_RW(ErrorType, GraphErrorType);
+        OBSERVABLE_NAMED_PROPERTY_RW(int, GraphErrorCode);
 
         property Windows::UI::Color LineColor
         {