From c3ee6a71e7510c1a63ae65856315528914d97f5d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C3=A9a=20Saviot?= <lea.saviot@numworks.com>
Date: Tue, 3 Sep 2019 13:57:06 +0200
Subject: [PATCH] [apps/graph] Fix computeYRange for polar/cartesian functions

Was very slow, compute only 1000 values to evaluate the yRange
---
 apps/graph/graph/graph_controller.cpp     | 6 +++++-
 apps/shared/cartesian_function.h          | 3 +++
 apps/shared/function.h                    | 1 +
 apps/shared/function_graph_controller.cpp | 9 +++++----
 4 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/apps/graph/graph/graph_controller.cpp b/apps/graph/graph/graph_controller.cpp
index f9d57c416..da2b65023 100644
--- a/apps/graph/graph/graph_controller.cpp
+++ b/apps/graph/graph/graph_controller.cpp
@@ -75,12 +75,16 @@ void GraphController::interestingRanges(float * xm, float * xM, float * ym, floa
       double tMax = f->tMax();
       assert(!std::isnan(tMin));
       assert(!std::isnan(tMax));
-      interestingFunctionRange(f, tMin, tMax, (tMax - tMin)/30, &resultxMin, &resultxMax, &resultyMin, &resultyMax);
+      assert(!std::isnan(f->rangeStep()));
+      interestingFunctionRange(f, tMin, tMax, f->rangeStep(), &resultxMin, &resultxMax, &resultyMin, &resultyMax);
     }
   } else {
     resultxMin = xMin;
     resultxMax = xMax;
   }
+  /* In practice, a step smaller than a pixel's width is needed for sampling
+   * the values of a function. Otherwise some relevant extremal values may be
+   * missed. */
   const float step = const_cast<GraphController *>(this)->curveView()->pixelWidth() / 2;
   for (int i = 0; i < functionStore()->numberOfActiveFunctions(); i++) {
     ExpiringPointer<CartesianFunction> f = functionStore()->modelForRecord(functionStore()->activeRecordAtIndex(i));
diff --git a/apps/shared/cartesian_function.h b/apps/shared/cartesian_function.h
index 4991b5abb..a9f585e12 100644
--- a/apps/shared/cartesian_function.h
+++ b/apps/shared/cartesian_function.h
@@ -50,7 +50,10 @@ public:
   double tMax() const override;
   void setTMin(double tMin);
   void setTMax(double tMax);
+  float rangeStep() const override { return (tMax() - tMin())/k_polarParamRangeSearchNumberOfPoints; }
+
 private:
+  constexpr static float k_polarParamRangeSearchNumberOfPoints = 100.0f; // This is ad hoc, no special justification
   template <typename T> Poincare::Coordinate2D<T> privateEvaluateXYAtParameter(T t, Poincare::Context * context) const;
   /* CartesianFunctionRecordDataBuffer is the layout of the data buffer of Record
    * representing a CartesianFunction. See comment on
diff --git a/apps/shared/function.h b/apps/shared/function.h
index 3ee7ceb7d..0193db9c3 100644
--- a/apps/shared/function.h
+++ b/apps/shared/function.h
@@ -37,6 +37,7 @@ public:
   virtual bool shouldClipTRangeToXRange() const { return true; } // Returns true if the function will not be displayed if t is outside x range.
   virtual double tMin() const { return NAN; }
   virtual double tMax() const { return NAN; }
+  virtual float rangeStep() const { return NAN; }
 
   // Name
   int nameWithArgument(char * buffer, size_t bufferSize);
diff --git a/apps/shared/function_graph_controller.cpp b/apps/shared/function_graph_controller.cpp
index 38a02e780..88b93f686 100644
--- a/apps/shared/function_graph_controller.cpp
+++ b/apps/shared/function_graph_controller.cpp
@@ -81,10 +81,6 @@ InteractiveCurveViewRangeDelegate::Range FunctionGraphController::computeYRange(
   float max = -FLT_MAX;
   float xMin = interactiveCurveViewRange->xMin();
   float xMax = interactiveCurveViewRange->xMax();
-  /* In practice, a step smaller than a pixel's width is needed for sampling
-   * the values of a function. Otherwise some relevant extremal values may be
-   * missed. */
-  const float step = curveView()->pixelWidth() / 2;
   assert(functionStore()->numberOfActiveFunctions() > 0);
   for (int i = 0; i < functionStore()->numberOfActiveFunctions(); i++) {
     ExpiringPointer<Function> f = functionStore()->modelForRecord(functionStore()->activeRecordAtIndex(i));
@@ -102,6 +98,11 @@ InteractiveCurveViewRangeDelegate::Range FunctionGraphController::computeYRange(
     } else if (f->shouldClipTRangeToXRange()) {
       tMax = minFloat(tMax, xMax);
     }
+  /* In practice, a step smaller than a pixel's width is needed for sampling
+   * the values of a function. Otherwise some relevant extremal values may be
+   * missed. */
+    float rangeStep = f->rangeStep();
+    const float step = std::isnan(rangeStep) ? curveView()->pixelWidth() / 2.0f : rangeStep;
     const int balancedBound = std::floor((tMax-tMin)/2/step);
     for (int j = -balancedBound; j <= balancedBound ; j++) {
       float t = (tMin+tMax)/2 + step * j;