From 56d23c213d693ca8ee87aee740cca6fc12bd20fa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89milie=20Feral?= <emilie.feral@numworks.com>
Date: Mon, 4 Jun 2018 16:54:43 +0200
Subject: [PATCH] [solver] Delete equation at first backspace event (instead of
 clearing the expression as in Graph/Sequence)

---
 apps/shared/expression_model.h                   | 3 +++
 apps/shared/expression_model_list_controller.cpp | 2 +-
 apps/solver/equation.h                           | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/apps/shared/expression_model.h b/apps/shared/expression_model.h
index 8482e9f04..d511abe03 100644
--- a/apps/shared/expression_model.h
+++ b/apps/shared/expression_model.h
@@ -20,6 +20,9 @@ public:
   Poincare::ExpressionLayout * layout();
   virtual bool isDefined();
   virtual bool isEmpty();
+  virtual bool shouldBeClearedBeforeRemove() {
+    return !isEmpty();
+  }
   virtual void setContent(const char * c);
   virtual void tidy();
 private:
diff --git a/apps/shared/expression_model_list_controller.cpp b/apps/shared/expression_model_list_controller.cpp
index b720aca9e..cb09deb82 100644
--- a/apps/shared/expression_model_list_controller.cpp
+++ b/apps/shared/expression_model_list_controller.cpp
@@ -70,7 +70,7 @@ bool ExpressionModelListController::handleEventOnExpression(Ion::Events::Event e
   }
   if (event == Ion::Events::Backspace && !isAddEmptyRow(selectedRow())) {
     ExpressionModel * model = modelStore()->modelAtIndex(modelIndexForRow(selectedRow()));
-    if (!model->isEmpty()) {
+    if (model->shouldBeClearedBeforeRemove()) {
       reinitExpression(model);
     } else {
       if (removeModelRow(model)) {
diff --git a/apps/solver/equation.h b/apps/solver/equation.h
index e615454cc..3fa925cb0 100644
--- a/apps/solver/equation.h
+++ b/apps/solver/equation.h
@@ -15,6 +15,9 @@ public:
   Equation(Equation&& other) = delete;
   void setContent(const char * c) override;
   void tidy() override;
+  bool shouldBeClearedBeforeRemove() override {
+    return false;
+  }
   Poincare::Expression * standardForm(Poincare::Context * context) const;
 private:
   mutable Poincare::Expression * m_standardForm;