[apps/sequence][apps/graph] fix behaviour when deleting functions

Change-Id: Ieccc85887fa0077446aaf57fee105b7fd2f3bff9

apps/sequence/sequence.cpp

@@ -223,6 +223,17 @@ bool Sequence::isDefined() {
   }
 }
 
+bool Sequence::isEmpty() {
+  switch (m_type) {
+    case Type::Explicite:
+      return Function::isEmpty();
+    case Type::SingleRecurrence:
+      return Function::isEmpty() && strlen(m_firstInitialConditionText) == 0;
+    default:
+      return Function::isEmpty() && strlen(m_firstInitialConditionText) == 0 && strlen(m_secondInitialConditionText) == 0;
+  }
+}
+
 float Sequence::evaluateAtAbscissa(float x, Poincare::Context * context) const {
   float n = roundf(x);
   switch (m_type) {

apps/sequence/sequence.h

@@ -35,6 +35,7 @@ public:
   Poincare::ExpressionLayout * firstInitialConditionName();
   Poincare::ExpressionLayout * secondInitialConditionName();
   bool isDefined() override;
+  bool isEmpty() override;
   float evaluateAtAbscissa(float x, Poincare::Context * context) const override;
   float sumOfTermsBetweenAbscissa(float start, float end, Poincare::Context * context);
 private:

apps/shared/function.cpp

@@ -83,6 +83,10 @@ void Function::setActive(bool active) {
   m_active = active;
 }
 
+bool Function::isEmpty() {
+  return strlen(m_text) == 0;
+}
+
 float Function::evaluateAtAbscissa(float x, Poincare::Context * context) const {
   Poincare::VariableContext variableContext = Poincare::VariableContext(symbol(), context);
   Poincare::Symbol xSymbol = Poincare::Symbol(symbol());

apps/shared/function.h

@@ -23,6 +23,7 @@ public:
   virtual bool isDefined();
   bool isActive();
   void setActive(bool active);
+  virtual bool isEmpty();
   virtual void setContent(const char * c);
   void setColor(KDColor m_color);
   virtual float evaluateAtAbscissa(float x, Poincare::Context * context) const;

apps/shared/list_controller.cpp

@@ -208,7 +208,7 @@ bool ListController::handleEvent(Ion::Events::Event event) {
   if (event == Ion::Events::Backspace && selectedRow() >= 0 &&
       (selectedRow() < numberOfRows() - 1 || m_functionStore->numberOfFunctions()  == m_functionStore->maxNumberOfFunctions())) {
     Shared::Function * function = m_functionStore->functionAtIndex(functionIndexForRow(selectedRow()));
-    if (selectedColumn() == 1) {
+    if (selectedColumn() == 1 && !function->isEmpty()) {
       reinitExpression(function);
     } else {
       removeFunctionRow(function);