[apps/graph] Fixed cache step quirks

Change-Id: I5b630301ab2a4b17a5a4d77c7d9a05120449e55e

apps/graph/graph/graph_view.cpp

@@ -40,18 +40,8 @@ void GraphView::drawRect(KDContext * ctx, KDRect rect) const {
     }
     float tmin = f->tMin();
     float tmax = f->tMax();
-    /* The step is a fraction of tmax-tmin. We will evaluate the function at
+
-     * every step and if the consecutive dots are close enough, we won't
+    float tstep = (tmax-tmin)/k_graphStepDenominator;
-     * evaluate any more dot within the step. We pick a very strange fraction
-     * denominator to avoid evaluating a periodic function periodically. For
-     * example, if tstep was (tmax - tmin)/10, the polar function r(θ) = sin(5θ)
-     * defined on 0..2π would be evaluated on r(0) = 0, r(π/5) = 0, r(2*π/5) = 0
-     * which would lead to no curve at all. With 10.0938275501223, the
-     * problematic functions are the functions whose period is proportionned to
-     * 10.0938275501223 which are hopefully rare enough.
-     * TODO: The drawCurve algorithm should use the derivative function to know
-     * how fast the function moves... */
-    float tstep = (tmax-tmin)/10.0938275501223f;
 
     float tCacheMin, tCacheStep;
     if (type == ContinuousFunction::PlotType::Cartesian) {
@@ -60,7 +50,7 @@ void GraphView::drawRect(KDContext * ctx, KDRect rect) const {
       tCacheStep = pixelWidth();
     } else {
       tCacheMin = tmin;
-      tCacheStep = tstep;
+      tCacheStep = tstep / ContinuousFunctionCache::k_parametricStepFactor;
     }
     ContinuousFunctionCache::PrepareForCaching(f.operator->(), cch, tCacheMin, tCacheStep);
 

apps/graph/graph/graph_view.h

@@ -7,6 +7,19 @@ namespace Graph {
 
 class GraphView : public Shared::FunctionGraphView {
 public:
+  /* The step is a fraction of tmax-tmin. We will evaluate the function at
+   * every step and if the consecutive dots are close enough, we won't
+   * evaluate any more dot within the step. We pick a very strange fraction
+   * denominator to avoid evaluating a periodic function periodically. For
+   * example, if tstep was (tmax - tmin)/10, the polar function r(θ) = sin(5θ)
+   * defined on 0..2π would be evaluated on r(0) = 0, r(π/5) = 0, r(2*π/5) = 0
+   * which would lead to no curve at all. With 10.0938275501223, the
+   * problematic functions are the functions whose period is proportionned to
+   * 10.0938275501223 which are hopefully rare enough.
+   * TODO: The drawCurve algorithm should use the derivative function to know
+   * how fast the function moves... */
+  static constexpr float k_graphStepDenominator = 10.0938275501223f;
+
   GraphView(Shared::InteractiveCurveViewRange * graphRange,
     Shared::CurveViewCursor * cursor, Shared::BannerView * bannerView, Shared::CursorView * cursorView);
   void reload() override;

apps/shared/continuous_function_cache.cpp

@@ -7,6 +7,7 @@ namespace Shared {
 constexpr int ContinuousFunctionCache::k_sizeOfCache;
 constexpr float ContinuousFunctionCache::k_cacheHitTolerance;
 constexpr int ContinuousFunctionCache::k_numberOfAvailableCaches;
+constexpr int ContinuousFunctionCache::k_parametricStepFactor;
 
 // public
 void ContinuousFunctionCache::PrepareForCaching(void * fun, ContinuousFunctionCache * cache, float tMin, float tStep) {
@@ -44,13 +45,6 @@ Poincare::Coordinate2D<float> ContinuousFunctionCache::valueForParameter(const C
 }
 
 // private
-float ContinuousFunctionCache::StepFactor(ContinuousFunction * function) {
-  /* When drawing a parametric or polar curve, the range is first divided by
-   * ~10,9, creating 11 intervals which are filled by dichotomy.
-   * We memoize 16 values for each of the 10 big intervals. */
-  return (function->plotType() == ContinuousFunction::PlotType::Cartesian) ? 1.f : 16.f;
-}
-
 void ContinuousFunctionCache::invalidateBetween(int iInf, int iSup) {
   for (int i = iInf; i < iSup; i++) {
     m_cache[i] = NAN;
@@ -59,7 +53,7 @@ void ContinuousFunctionCache::invalidateBetween(int iInf, int iSup) {
 
 void ContinuousFunctionCache::setRange(ContinuousFunction * function, float tMin, float tStep) {
   m_tMin = tMin;
-  m_tStep = tStep / StepFactor(function);
+  m_tStep = tStep;
 }
 
 int ContinuousFunctionCache::indexForParameter(const ContinuousFunction * function, float t) const {

apps/shared/continuous_function_cache.h

@@ -1,6 +1,7 @@
 #ifndef SHARED_CONTINUOUS_FUNCTION_CACHE_H
 #define SHARED_CONTINUOUS_FUNCTION_CACHE_H
 
+#include "../graph/graph/graph_view.h"
 #include <ion/display.h>
 #include <poincare/context.h>
 #include <poincare/coordinate_2D.h>
@@ -10,10 +11,13 @@ namespace Shared {
 class ContinuousFunction;
 
 class ContinuousFunctionCache {
-public:
+private:
   /* The size of the cache is chosen to optimize the display of cartesian
-   * function */
+   * functions */
+   static constexpr int k_sizeOfCache = Ion::Display::Width;
+public:
   static constexpr int k_numberOfAvailableCaches = 2;
+  static constexpr int k_parametricStepFactor = k_sizeOfCache / int(Graph::GraphView::k_graphStepDenominator);
 
   static void PrepareForCaching(void * fun, ContinuousFunctionCache * cache, float tMin, float tStep);
 
@@ -23,13 +27,8 @@ public:
   void clear();
   Poincare::Coordinate2D<float> valueForParameter(const ContinuousFunction * function, Poincare::Context * context, float t);
 private:
-  /* The size of the cache is chosen to optimize the display of cartesian
-   * function */
-  static constexpr int k_sizeOfCache = Ion::Display::Width;
   static constexpr float k_cacheHitTolerance = 1e-3;
 
-  static float StepFactor(ContinuousFunction * function);
-
   void invalidateBetween(int iInf, int iSup);
   void setRange(ContinuousFunction * function, float tMin, float tStep);
   int indexForParameter(const ContinuousFunction * function, float t) const;