[interactive_curve_view_controller] Fix Cursor

Restore the permanence of the cursor between accesses to the graph
window.
The cursor used to be reset when the models had been modified. As there
is no longer a system in place to track these modifications, we manually
check if there is a curve beneath the cursor before reseting it.

Change-Id: I6f71fc17744b5bf1ee552c82126bb4a08b823629

apps/regression/graph_controller.cpp

@@ -259,6 +259,21 @@ void GraphController::initCursorParameters() {
   *m_selectedDotIndex = m_store->numberOfPairsOfSeries(*m_selectedSeriesIndex);
 }
 
+bool GraphController::isCursorHanging() {
+  if (m_store->seriesIsEmpty(*m_selectedSeriesIndex)) {
+    return true;
+  }
+  Coordinate2D<double> xy;
+  if (*m_selectedDotIndex == -1) {
+    xy = xyValues(*m_selectedSeriesIndex, m_cursor->t(), globalContext());
+  } else if (*m_selectedDotIndex == m_store->numberOfPairsOfSeries(*m_selectedSeriesIndex)) {
+    xy = Coordinate2D<double>(m_store->meanOfColumn(*m_selectedSeriesIndex, 0), m_store->meanOfColumn(*m_selectedSeriesIndex, 1));
+  } else {
+    xy = Coordinate2D<double>(m_store->get(*m_selectedSeriesIndex, 0, *m_selectedDotIndex), m_store->get(*m_selectedSeriesIndex, 1, *m_selectedDotIndex));
+  }
+  return xy.x1() != m_cursor->x() || xy.x2() != m_cursor->y();
+}
+
 bool GraphController::moveCursorVertically(int direction) {
   Poincare::Context * context = globalContext();
   double x = m_cursor->x();

apps/regression/graph_controller.h

@@ -40,6 +40,7 @@ private:
 
   // InteractiveCurveViewController
   void initCursorParameters() override;
+  bool isCursorHanging() override;
   uint32_t rangeVersion() override;
   int selectedCurveIndex() const override { return *m_selectedSeriesIndex; }
   bool closestCurveIndexIsSuitable(int newIndex, int currentIndex) const override;

apps/shared/function_graph_controller.cpp

@@ -116,6 +116,16 @@ bool FunctionGraphController::moveCursorVertically(int direction) {
   return true;
 }
 
+bool FunctionGraphController::isCursorHanging() {
+  Poincare::Context * context = textFieldDelegateApp()->localContext();
+  if (indexFunctionSelectedByCursor() >= functionStore()->numberOfActiveFunctions()) {
+    return true;
+  }
+  ExpiringPointer<Function> f = functionStore()->modelForRecord(functionStore()->activeRecordAtIndex(indexFunctionSelectedByCursor()));
+  Coordinate2D<double> xy = f->evaluateXYAtParameter(m_cursor->t(), context);
+  return xy.x1() != m_cursor->x() || xy.x2() != m_cursor->y();
+}
+
 CurveView * FunctionGraphController::curveView() {
   return functionGraphView();
 }

apps/shared/function_graph_controller.h

@@ -37,6 +37,7 @@ protected:
   Poincare::Coordinate2D<double> xyValues(int curveIndex, double t, Poincare::Context * context) const override;
   int numberOfCurves() const override;
   void initCursorParameters() override;
+  bool isCursorHanging() override;
   CurveView * curveView() override;
 
   void yRangeForCursorFirstMove(Shared::InteractiveCurveViewRange * range) const;

apps/shared/interactive_curve_view_controller.cpp

@@ -156,7 +156,11 @@ void InteractiveCurveViewController::viewWillAppear() {
 
   /* Warning: init cursor parameter before reloading banner view. Indeed,
    * reloading banner view needs an updated cursor to load the right data. */
-  initCursorParameters();
+  uint32_t newRangeVersion = rangeVersion();
+  if ((*m_rangeVersion != newRangeVersion && !isCursorVisible()) || isCursorHanging()) {
+    initCursorParameters();
+  }
+  *m_rangeVersion = newRangeVersion;
 
   curveView()->setOkView(&m_okView);
   if (!curveView()->isMainViewSelected()) {

apps/shared/interactive_curve_view_controller.h

@@ -40,6 +40,7 @@ protected:
   virtual bool moveCursorVertically(int direction) = 0;
   virtual uint32_t rangeVersion() = 0;
   bool isCursorVisible();
+  virtual bool isCursorHanging() = 0;
 
   // Closest vertical curve helper
   int closestCurveIndexVertically(bool goingUp, int currentSelectedCurve, Poincare::Context * context) const;