Add variable editing (#581)

src/GraphingInterfaces/Common.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <memory>
+#include <string>
 
 #ifndef GRAPHINGAPI
 #ifdef GRAPHING_ENGINE_IMPL
@@ -38,6 +39,14 @@ namespace Graphing
         virtual bool IsEmptySet() const = 0;
     };
 
+    struct IVariable
+    {
+        virtual ~IVariable() = default;
+
+        virtual int GetVariableID() const = 0;
+        virtual const std::wstring& GetVariableName() = 0;
+    };
+
     struct IExpressible
     {
         virtual ~IExpressible() = default;

src/GraphingInterfaces/IGraph.h

@@ -16,6 +16,10 @@ namespace Graphing
 
         virtual IGraphingOptions& GetOptions() = 0;
 
+        virtual std::vector<std::shared_ptr<IVariable>> GetVariables() = 0;
+
+        virtual void SetArgValue(std::wstring variableName, double value) = 0;
+
         virtual std::shared_ptr< Renderer::IGraphRenderer > GetRenderer() const = 0;
 
         virtual bool TryResetSelection() = 0;