From 8ce9f363ada28362a77c26d86d02f1e650ef0638 Mon Sep 17 00:00:00 2001
From: Gabriel Ozouf <gabriel.ozouf@numworks.com>
Date: Wed, 14 Oct 2020 11:15:35 +0200
Subject: [PATCH] [interactive_curve_view_range] Force equal axes

Added a tolerance when checking orthonormality, so that ranges that are
nearly orthonormal will be made orthonormal.

Change-Id: Ie3bf076086561e3ff6374e7daa9dd1a884c52d5a
---
 apps/shared/interactive_curve_view_range.cpp | 8 ++++----
 apps/shared/interactive_curve_view_range.h   | 3 ++-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/apps/shared/interactive_curve_view_range.cpp b/apps/shared/interactive_curve_view_range.cpp
index a0c91610d..90b35fa0e 100644
--- a/apps/shared/interactive_curve_view_range.cpp
+++ b/apps/shared/interactive_curve_view_range.cpp
@@ -115,7 +115,7 @@ void InteractiveCurveViewRange::setDefault() {
 
   // Compute the interesting range
   m_delegate->interestingRanges(this);
-  bool revertToNormalized = isOrthonormal();
+  bool revertToNormalized = isOrthonormal(k_orthonormalTolerance);
 
   // Add margins
   float xRange = xMax() - xMin();
@@ -198,8 +198,8 @@ void InteractiveCurveViewRange::checkForNormalizedRange() {
 }
 
 bool InteractiveCurveViewRange::isOrthonormal(float tolerance) const {
-  float pixelHeight = std::round(Ion::Display::Height * (NormalizedYHalfRange(100.f) / Ion::Display::HeightInTenthOfMillimeter));
-  float pixelWidth = std::round(Ion::Display::Width * (NormalizedXHalfRange(100.f) / Ion::Display::WidthInTenthOfMillimeter));
-  return std::fabs(std::round(pixelHeight * (xMax() - xMin())) - std::round(pixelWidth * (yMax() - yMin()))) <= tolerance;
+  float ratio = (yMax() - yMin()) / (xMax() - xMin());
+  float ratioDifference = std::fabs(std::log(ratio / NormalYXRatio()));
+  return  ratioDifference <= tolerance;
 }
 }
diff --git a/apps/shared/interactive_curve_view_range.h b/apps/shared/interactive_curve_view_range.h
index b0c8d38c9..f9c933e85 100644
--- a/apps/shared/interactive_curve_view_range.h
+++ b/apps/shared/interactive_curve_view_range.h
@@ -19,7 +19,7 @@ public:
   {}
 
   static constexpr float NormalYXRatio() { return NormalizedYHalfRange(1.f) / NormalizedXHalfRange(1.f); }
-  bool isOrthonormal(float tolerance = 0.f) const;
+  bool isOrthonormal(float tolerance = 2 * FLT_EPSILON) const;
 
   void setDelegate(InteractiveCurveViewRangeDelegate * delegate) { m_delegate = delegate; }
   uint32_t rangeChecksum() override;
@@ -52,6 +52,7 @@ protected:
   constexpr static float k_upperMaxFloat = 1E+8f;
   constexpr static float k_lowerMaxFloat = 9E+7f;
   constexpr static float k_maxRatioPositionRange = 1E5f;
+  constexpr static float k_orthonormalTolerance = 0.2f;
   static float clipped(float x, bool isMax) { return Range1D::clipped(x, isMax, k_lowerMaxFloat, k_upperMaxFloat); }
   /* In normalized settings, we put each axis so that 1cm = 2 units. For now,
    * the screen has size 43.2mm * 57.6mm.