From 2fb6824947d7a37556ffb7e145b186227dc628b4 Mon Sep 17 00:00:00 2001
From: Ruben Dashyan <ruben.dashyan@numworks.com>
Date: Fri, 10 May 2019 14:22:12 +0200
Subject: [PATCH] [apps/shared/interactive_curve_view_controller] Rewrite
 comment about addMargin

---
 .../interactive_curve_view_controller.cpp     | 43 ++++++++-----------
 1 file changed, 17 insertions(+), 26 deletions(-)

diff --git a/apps/shared/interactive_curve_view_controller.cpp b/apps/shared/interactive_curve_view_controller.cpp
index aa3a0e31c..2480f24c1 100644
--- a/apps/shared/interactive_curve_view_controller.cpp
+++ b/apps/shared/interactive_curve_view_controller.cpp
@@ -35,38 +35,29 @@ InteractiveCurveViewController::InteractiveCurveViewController(Responder * paren
 {
 }
 
-float InteractiveCurveViewController::addMargin(float x, float range, bool isVertical, bool isMin) {
-  /* We are adding margins. Let's name:
-   *   - The current range: rangeBefore
-   *   - The next range: rangeAfter
-   *   - The bottom margin ratio with which we will evaluate if a point is too
-   *       low on the screen: bottomRatioAfter
-   *   - The bottom margin ratio with which we will evaluate if a point is too
-   *       high on the screen: topRatioAfter
-   *   - The ratios we need to use to create the margins: bottomRatioBefore and
-   *       topRatioBefore
-   *
-   * We want to add margins so that:
-   *   bottomRatioAfter*rangeAfter == bottomRatioBefore * rangeBefore
-   *   topRatioAfter*rangeAfter == topRatioBefore * rangeBefore
-   * Knowing that:
-   *   rangeAfter = (1+bottomRatioBefore+topRatioBefore)*rangeBefore
-   *
-   * We thus have:
-   *   bottomRatioBefore = bottomRatioAfter / (1-bottomRatioAfter-topRatioAfter)
-   *   topRatioBefore = topRatioAfter / (1-bottomRatioAfter-topRatioAfter)
-   *
-   * If we just used bottomRatioBefore = bottomRatioAfter and
-   * topRatioBefore = topRatioAfter, we would create too small margins and the
-   * controller might need to pan right after a Y auto calibration. */
-
+float InteractiveCurveViewController::addMargin(float y, float range, bool isVertical, bool isMin) {
+  /* The provided min or max range limit y is altered by adding a margin.
+   * In pixels, the view's height occupied by the vertical range is equal to
+   *   viewHeight - topMargin - bottomMargin.
+   * Hence one pixel must correspond to
+   *   range / (viewHeight - topMargin - bottomMargin).
+   * Finally, adding topMargin pixels of margin, say at the top, comes down
+   * to adding
+   *   range * topMargin / (viewHeight - topMargin - bottomMargin)
+   * which is equal to
+   *   range * topMarginRatio / ( 1 - topMarginRatio - bottomMarginRatio)
+   * where
+   *   topMarginRation = topMargin / viewHeight
+   *   bottomMarginRatio = bottomMargin / viewHeight.
+   * The same goes horizontally.
+   */
   float topMarginRatio = isVertical ? cursorTopMarginRatio() : k_cursorRightMarginRatio;
   float bottomMarginRatio = isVertical ? cursorBottomMarginRatio() : k_cursorLeftMarginRatio;
   assert(topMarginRatio + bottomMarginRatio < 1); // Assertion so that the formula is correct
   float ratioDenominator = 1 - bottomMarginRatio - topMarginRatio;
   float ratio = isMin ? -bottomMarginRatio : topMarginRatio;
   ratio = ratio / ratioDenominator;
-  return x+ratio*range;
+  return y + ratio * range;
 }
 
 const char * InteractiveCurveViewController::title() {