[poincare/zoom] Handle undefined functions

Rework the logic so that :
  - an undefined function will be displayed with a clealry defined
    null range.
  - display both an undefined function and a correct function at the
    same time will not affect the correct range.

Change-Id: Ife9dc0d2ace667cab5a6b8826347078fca33e4d5

apps/shared/continuous_function.cpp

@@ -285,10 +285,39 @@ void ContinuousFunction::rangeForDisplay(float * xMin, float * xMax, float * yMi
   };
 
   if (fullyComputed) {
+    /* The function has points of interest. */
     Zoom::RefinedYRangeForDisplay(evaluation, *xMin, *xMax, yMin, yMax, context, this);
-  } else {
-    Zoom::RangeWithRatioForDisplay(evaluation, InteractiveCurveViewRange::NormalYXRatio(), xMin, xMax, yMin, yMax, context, this);
+    return;
   }
+
+  /* Try to display an orthonormal range. */
+  Zoom::RangeWithRatioForDisplay(evaluation, InteractiveCurveViewRange::NormalYXRatio(), xMin, xMax, yMin, yMax, context, this);
+  if (std::isfinite(*xMin) && std::isfinite(*xMax) && std::isfinite(*yMin) && std::isfinite(*yMax)) {
+    return;
+  }
+
+  /* The function's profile is not great for an orthonormal range.
+   * Try a basic range. */
+  *xMin = - Zoom::k_defaultHalfRange;
+  *xMax = Zoom::k_defaultHalfRange;
+  Zoom::RefinedYRangeForDisplay(evaluation, *xMin, *xMax, yMin, yMax, context, this);
+  if (std::isfinite(*xMin) && std::isfinite(*xMax) && std::isfinite(*yMin) && std::isfinite(*yMax)) {
+    return;
+  }
+
+  /* The function's order of magnitude cannot be computed. Try to just display
+   * the full function. */
+  float step =  (*xMax - *xMin) / k_polarParamRangeSearchNumberOfPoints;
+  Zoom::FullRange(evaluation, *xMin, *xMax, step, yMin, yMax, context, this);
+  if (std::isfinite(*xMin) && std::isfinite(*xMax) && std::isfinite(*yMin) && std::isfinite(*yMax)) {
+    return;
+  }
+
+  /* The function is probably undefined. */
+  *xMin = NAN;
+  *xMax = NAN;
+  *yMin = NAN;
+  *yMax = NAN;
 }
 
 void * ContinuousFunction::Model::expressionAddress(const Ion::Storage::Record * record) const {

apps/shared/function_graph_controller.cpp

@@ -160,12 +160,15 @@ void FunctionGraphController::interestingRanges(InteractiveCurveViewRange * rang
   float xMin, xMax, yMin, yMax;
   Poincare::Zoom::CombineRanges(length, xMins, xMaxs, &xMin, &xMax);
   Poincare::Zoom::CombineRanges(length, yMins, yMaxs, &yMin, &yMax);
-  range->setXMin(xMin);
-  range->setXMax(xMax);
-  range->setYMin(yMin);
-  range->setYMax(yMax);
-
-  yRangeForCursorFirstMove(range);
+  if (std::isfinite(xMin) && std::isfinite(xMax) && std::isfinite(yMin) && std::isfinite(yMax) && xMax > xMin && yMax > yMin) {
+    range->setXMin(xMin);
+    range->setXMax(xMax);
+    range->setYMin(yMin);
+    range->setYMax(yMax);
+    yRangeForCursorFirstMove(range);
+  } else {
+    range->setNullRange();
+  }
 }
 
 void FunctionGraphController::yRangeForCursorFirstMove(InteractiveCurveViewRange * range) const {

apps/shared/interactive_curve_view_range.cpp

@@ -134,6 +134,14 @@ void InteractiveCurveViewRange::setDefault() {
   normalize();
 }
 
+void InteractiveCurveViewRange::setNullRange() {
+  m_xRange.setMin(- Range1D::k_default);
+  setXMax(Range1D::k_default);
+  m_yRange.setMin(0);
+  m_yRange.setMax(0);
+  normalize();
+}
+
 void InteractiveCurveViewRange::centerAxisAround(Axis axis, float position) {
   if (std::isnan(position)) {
     return;

apps/shared/interactive_curve_view_range.h

@@ -44,6 +44,7 @@ public:
   void panWithVector(float x, float y);
   virtual void normalize();
   virtual void setDefault();
+  void setNullRange();
   void centerAxisAround(Axis axis, float position);
   void panToMakePointVisible(float x, float y, float topMarginRatio, float rightMarginRatio, float bottomMarginRation, float leftMarginRation, float pixelWidth);
   void checkForNormalizedRange();

poincare/src/zoom.cpp

@@ -146,8 +146,8 @@ bool Zoom::InterestingRangesForDisplay(ValueAtAbscissa evaluation, float * xMin,
   resultX[1] = std::max(resultX[1], asymptote[1]);
   if (resultX[0] >= resultX[1]) {
     /* Fallback to default range. */
-    resultX[0] = - k_defaultHalfRange;
-    resultX[1] = k_defaultHalfRange;
+    resultX[0] = NAN;
+    resultX[1] = NAN;
     return false;
   } else {
     resultX[0] = std::min(resultX[0], explosion[0]);
@@ -195,8 +195,9 @@ void Zoom::RefinedYRangeForDisplay(ValueAtAbscissa evaluation, float xMin, float
    * order of magnitude and is used to cut the Y range. */
 
   if (pop == 0) {
-    *yMin = 0;
-    *yMax = 0;
+    *yMin = NAN;
+    *yMax = NAN;
+    return;
   } else {
     float bound = std::exp(sum / pop + 1.f);
     sampleYMin = std::max(sampleYMin, - bound);
@@ -286,9 +287,10 @@ void Zoom::RangeWithRatioForDisplay(ValueAtAbscissa evaluation, float yxRatio, f
     xMagnitude *= 10.f;
   }
   if (bestGrade == FLT_MAX) {
-    *xMin = -k_defaultHalfRange;
-    *xMax = k_defaultHalfRange;
-    RefinedYRangeForDisplay(evaluation, *xMin, *xMax, yMin, yMax, context, auxiliary);
+    *xMin = NAN;
+    *xMax = NAN;
+    *yMin = NAN;
+    *yMax = NAN;
     return;
   }
 
@@ -309,6 +311,10 @@ void Zoom::FullRange(ValueAtAbscissa evaluation, float tMin, float tMax, float t
     }
     t += tStep;
   }
+  if (*fMin > *fMax) {
+    *fMin = NAN;
+    *fMax = NAN;
+  }
 }
 
 void Zoom::RangeFromSingleValue(float value, float * boundMin, float * boundMax) {