GraphApp: Use a FunctionStore

Change-Id: Ib75947c40167489726fafc493ccb0ebf2862142b

apps/graph/function.cpp

@@ -0,0 +1,43 @@
+#include "function.h"
+
+Graph::Function::Function() :
+  m_text(nullptr),
+  m_expression(nullptr),
+  m_layout(nullptr)
+{
+}
+
+Graph::Function::Function(const char * text) :
+  m_text(text), // FIXME: Copy !!
+  m_expression(nullptr),
+  m_layout(nullptr)
+{
+}
+
+Graph::Function::~Function() {
+  //FIXME: Free m_text!
+  if (m_layout != nullptr) {
+    delete m_layout;
+  }
+  if (m_expression != nullptr) {
+    delete m_expression;
+  }
+}
+
+const char * Graph::Function::text() {
+  return m_text;
+}
+
+Expression * Graph::Function::expression() {
+  if (m_expression == nullptr) {
+    m_expression = Expression::parse(m_text);
+  }
+  return m_expression;
+}
+
+ExpressionLayout * Graph::Function::layout() {
+  if (m_layout == nullptr) {
+    m_layout = expression()->createLayout();
+  }
+  return m_layout;
+}