From 094d4ebf2a0546ff418b76052a250e72a7ec3a75 Mon Sep 17 00:00:00 2001
From: Alexey Kulish <alexey.kulish@osmand.net>
Date: Thu, 9 Mar 2017 11:24:51 +0300
Subject: [PATCH] Added interpolation of Y value when two charts visible

---
 OsmAnd-java/src/net/osmand/util/MapUtils.java | 16 ++++++++++-
 .../net/osmand/plus/helpers/GpxUiHelper.java  | 28 +++++++++++++++----
 2 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/OsmAnd-java/src/net/osmand/util/MapUtils.java b/OsmAnd-java/src/net/osmand/util/MapUtils.java
index b71e03f31b..6046e985c7 100644
--- a/OsmAnd-java/src/net/osmand/util/MapUtils.java
+++ b/OsmAnd-java/src/net/osmand/util/MapUtils.java
@@ -586,7 +586,21 @@ public class MapUtils {
 		return rect;
 	}
 
-	
+	public static float getInterpolatedY(float x1, float y1, float x2, float y2, float x) {
+
+		float a = y1 - y2;
+		float b = x2 - x1;
+
+		float d = -a * b;
+		if (d != 0) {
+			float c1 = y2 * x1 - x2 * y1;
+			float c2 = x * (y2 - y1);
+
+			return (a * (c1 - c2)) / d;
+		} else {
+			return y1;
+		}
+	}
 }
 
 
diff --git a/OsmAnd/src/net/osmand/plus/helpers/GpxUiHelper.java b/OsmAnd/src/net/osmand/plus/helpers/GpxUiHelper.java
index ebff0a5bf0..280f39d7f9 100644
--- a/OsmAnd/src/net/osmand/plus/helpers/GpxUiHelper.java
+++ b/OsmAnd/src/net/osmand/plus/helpers/GpxUiHelper.java
@@ -41,6 +41,7 @@ import com.github.mikephil.charting.components.MarkerView;
 import com.github.mikephil.charting.components.XAxis;
 import com.github.mikephil.charting.components.YAxis;
 import com.github.mikephil.charting.data.ChartData;
+import com.github.mikephil.charting.data.DataSet;
 import com.github.mikephil.charting.data.Entry;
 import com.github.mikephil.charting.data.LineDataSet;
 import com.github.mikephil.charting.formatter.IAxisValueFormatter;
@@ -79,6 +80,7 @@ import net.osmand.plus.monitoring.OsmandMonitoringPlugin;
 import net.osmand.render.RenderingRuleProperty;
 import net.osmand.render.RenderingRulesStorage;
 import net.osmand.util.Algorithms;
+import net.osmand.util.MapUtils;
 
 import java.io.File;
 import java.text.DateFormat;
@@ -1606,24 +1608,24 @@ public class GpxUiHelper {
 						break;
 				}
 				if (altSetIndex != -1) {
-					Entry eAlt = chartData.getEntryForHighlight(new Highlight(e.getX(), Float.NaN, altSetIndex));
-					((TextView) textAltView.findViewById(R.id.text_alt_value)).setText(Integer.toString((int) eAlt.getY()) + " ");
+					float y = getInterpolatedY(altSetIndex == 0 ? dataSet1 : dataSet2, e);
+					((TextView) textAltView.findViewById(R.id.text_alt_value)).setText(Integer.toString((int) y) + " ");
 					((TextView) textAltView.findViewById(R.id.text_alt_units)).setText((altSetIndex == 0 ? dataSet1.units : dataSet2.units));
 					textAltView.setVisibility(VISIBLE);
 				} else {
 					textAltView.setVisibility(GONE);
 				}
 				if (spdSetIndex != -1) {
-					Entry eSpd = chartData.getEntryForHighlight(new Highlight(e.getX(), Float.NaN, spdSetIndex));
-					((TextView) textSpdView.findViewById(R.id.text_spd_value)).setText(Integer.toString((int) eSpd.getY()) + " ");
+					float y = getInterpolatedY(spdSetIndex == 0 ? dataSet1 : dataSet2, e);
+					((TextView) textSpdView.findViewById(R.id.text_spd_value)).setText(Integer.toString((int) y) + " ");
 					((TextView) textSpdView.findViewById(R.id.text_spd_units)).setText(spdSetIndex == 0 ? dataSet1.units : dataSet2.units);
 					textSpdView.setVisibility(VISIBLE);
 				} else {
 					textSpdView.setVisibility(GONE);
 				}
 				if (slpSetIndex != -1) {
-					Entry eSlp = chartData.getEntryForHighlight(new Highlight(e.getX(), Float.NaN, slpSetIndex));
-					((TextView) textSlpView.findViewById(R.id.text_slp_value)).setText(Integer.toString((int) eSlp.getY()) + " ");
+					float y = getInterpolatedY(slpSetIndex == 0 ? dataSet1 : dataSet2, e);
+					((TextView) textSlpView.findViewById(R.id.text_slp_value)).setText(Integer.toString((int) y) + " ");
 					textSlpView.setVisibility(VISIBLE);
 				} else {
 					textSlpView.setVisibility(GONE);
@@ -1638,6 +1640,20 @@ public class GpxUiHelper {
 			super.refreshContent(e, highlight);
 		}
 
+		private float getInterpolatedY(OrderedLineDataSet ds, Entry e) {
+			if (ds.getEntryIndex(e) == -1) {
+				Entry upEntry = ds.getEntryForXValue(e.getX(), Float.NaN, DataSet.Rounding.UP);
+				Entry downEntry = upEntry;
+				int upIndex = ds.getEntryIndex(upEntry);
+				if (upIndex > 0) {
+					downEntry = ds.getEntryForIndex(upIndex - 1);
+				}
+				return MapUtils.getInterpolatedY(downEntry.getX(), downEntry.getY(), upEntry.getX(), upEntry.getY(), e.getX());
+			} else {
+				return e.getY();
+			}
+		}
+
 		@Override
 		public MPPointF getOffset() {
 			if (getChartView().getData().getDataSetCount() == 2) {