Switch to RichEdit math mode in EquationTextBox (#672)

* Use RichEdit Math Mode

* Add comment

Co-Authored-By: Stephanie Anderl <46726333+sanderl@users.noreply.github.com>

src/GraphControl/Control/Equation.cpp

@@ -9,6 +9,9 @@ using namespace Windows::UI::Xaml;
 
 namespace GraphControl
 {
+    // Remove mml: formatting specific to RichEditBox control, which is not understood by the graph engine.
+    static constexpr wstring_view s_mathPrefix = L"mml:";
+
     DependencyProperty^ Equation::s_expressionProperty;
     static constexpr auto s_propertyName_Expression = L"Expression";
 
@@ -74,7 +77,7 @@ namespace GraphControl
         ss  << GetRequestHeader()
             << GetExpression()
             << GetLineColor()
-            << L")";
+            << L"</mfenced></mrow>";
 
         return ss.str();
     }
@@ -82,19 +85,28 @@ namespace GraphControl
     wstring Equation::GetRequestHeader()
     {
         wstring expr{ Expression->Data() };
-        if (expr.find(L"=") != wstring::npos)
+        if (expr.find(L">=<") != wstring::npos)
         {
-            return L"plotEq2d("s;
+            return L"<mrow><mi>plotEq2d</mi><mfenced separators=\"\">"s;
         }
         else
         {
-            return L"plot2d("s;
+            return L"<mrow><mi>plot2d</mi><mfenced separators=\"\">"s;
         }
     }
 
     wstring Equation::GetExpression()
     {
-        return Expression->Data();
+        wstring mathML = Expression->Data();
+
+        size_t mathPrefix = 0;
+        while ((mathPrefix = mathML.find(s_mathPrefix, mathPrefix)) != std::string::npos)
+        {
+            mathML.replace(mathPrefix, s_mathPrefix.length(), L"");
+            mathPrefix += s_mathPrefix.length();
+        }
+
+        return mathML;
     }
 
     wstring Equation::GetLineColor()

src/GraphControl/Control/Grapher.cpp

@@ -55,7 +55,7 @@ namespace GraphControl
         : m_solver{ IMathSolver::CreateMathSolver() }
         , m_graph{ m_solver->CreateGrapher() }
     {
-        m_solver->ParsingOptions().SetFormatType(FormatType::Linear);
+        m_solver->ParsingOptions().SetFormatType(FormatType::MathML);
 
         DefaultStyleKey = StringReference(s_defaultStyleKey);
 
@@ -365,20 +365,20 @@ namespace GraphControl
             if (!validEqs.empty())
             {
                 wstringstream ss{};
-                ss << L"show2d(";
+                ss << L"<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>show2d</mi><mfenced separators=\"\">";
 
                 int numValidEquations = 0;
                 for (Equation^ eq : validEqs)
                 {
                     if (numValidEquations++ > 0)
                     {
-                        ss << L",";
+                        ss << L"<mo>,</mo>";
                     }
 
                     ss << eq->GetRequest();
                 }
 
-                ss << L")";
+                ss << L"</mfenced></mrow></math>";
 
                 wstring request = ss.str();
                 unique_ptr<IExpression> graphExpression;

src/GraphControl/GraphControl.vcxproj

@@ -42,7 +42,7 @@
     <MinimumVisualStudioVersion>14.0</MinimumVisualStudioVersion>
     <AppContainerApplication>true</AppContainerApplication>
     <ApplicationType>Windows Store</ApplicationType>
-    <WindowsTargetPlatformVersion Condition="'$(WindowsTargetPlatformVersion)' == ''">10.0</WindowsTargetPlatformVersion>
+    <WindowsTargetPlatformVersion Condition="'$(WindowsTargetPlatformVersion)' == ''">10.0.18970.0</WindowsTargetPlatformVersion>
     <WindowsTargetPlatformMinVersion>10.0.18362.0</WindowsTargetPlatformMinVersion>
     <ApplicationTypeRevision>10.0</ApplicationTypeRevision>
   </PropertyGroup>