From b344772dced1455ea0b501d2be2ac89a17908303 Mon Sep 17 00:00:00 2001
From: Erik Johansson <erik@ejohansson.se>
Date: Wed, 22 Nov 2017 22:38:16 +0100
Subject: [PATCH] Use dynamic min and max values for gauge

Calculate min and max to put the normal zone in the middle while
keeping the current value visible. Makes it easier to see where one is
compared to the normal values.
---
 .../openscale/gui/views/LinearGaugeView.java  | 43 +++++++++++++------
 .../openscale/gui/views/MeasurementView.java  |  1 -
 2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/android_app/app/src/main/java/com/health/openscale/gui/views/LinearGaugeView.java b/android_app/app/src/main/java/com/health/openscale/gui/views/LinearGaugeView.java
index 82a29c17..bcc4bfcf 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/views/LinearGaugeView.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/views/LinearGaugeView.java
@@ -51,8 +51,6 @@ public class LinearGaugeView extends View {
     private Paint infoTextPaint;
 
     private float value;
-    private float minValue;
-    private float maxValue;
     private float firstLimit = -1.0f;
     private float secondLimit = -1.0f;
 
@@ -95,7 +93,7 @@ public class LinearGaugeView extends View {
         infoTextPaint.setTextAlign(Paint.Align.CENTER);
     }
 
-    private float valueToPosition(float value) {
+    private float valueToPosition(float value, float minValue, float maxValue) {
         final float percent = (value - minValue) / (maxValue - minValue) * 100.0f;
         return getWidth() / 100.0f * percent;
     }
@@ -123,9 +121,35 @@ public class LinearGaugeView extends View {
             return;
         }
 
-        final float firstPos = valueToPosition(firstLimit);
-        final float secondPos = valueToPosition(secondLimit);
-        final float valuePos = valueToPosition(value);
+        final boolean hasFirstLimit = firstLimit >= 0;
+
+        // Calculate the size of the "normal" span with a fallback if there is no such span
+        float span = hasFirstLimit ? secondLimit - firstLimit : 0.3f * secondLimit;
+
+        // Adjust the span if needed to make the value fit inside of it
+        if (hasFirstLimit && value < firstLimit - span) {
+            span = firstLimit - value;
+        } else if (!hasFirstLimit && value < secondLimit - span) {
+            span = secondLimit - value;
+        } else if (value > secondLimit + span) {
+            span = value - secondLimit;
+        }
+
+        // Round span to some nice value
+        if (span <= 1.0f) {
+            span = (float)Math.ceil(span * 10.0) / 10.0f;
+        } else if (span <= 10.0f) {
+            span = (float)Math.ceil(span);
+        } else {
+            span = 5.0f * (float)Math.ceil(span / 5.0);
+        }
+
+        final float minValue = Math.max(0.0f, (hasFirstLimit ? firstLimit : secondLimit) - span);
+        final float maxValue = secondLimit + span;
+
+        final float firstPos = valueToPosition(firstLimit, minValue, maxValue);
+        final float secondPos = valueToPosition(secondLimit, minValue, maxValue);
+        final float valuePos = valueToPosition(value, minValue, maxValue);
 
         // Bar
         final float barTop = getHeight() / 2.0f - barHeight / 2.0f;
@@ -221,13 +245,6 @@ public class LinearGaugeView extends View {
         setMeasuredDimension(width, height);
     }
 
-    public void setMinMaxValue(float min, float max) {
-        minValue = min;
-        maxValue = max;
-        invalidate();
-        requestLayout();
-    }
-
     public void setLimits(float first, float second) {
         firstLimit = first;
         secondLimit = second;
diff --git a/android_app/app/src/main/java/com/health/openscale/gui/views/MeasurementView.java b/android_app/app/src/main/java/com/health/openscale/gui/views/MeasurementView.java
index b3aa7458..cb392d15 100644
--- a/android_app/app/src/main/java/com/health/openscale/gui/views/MeasurementView.java
+++ b/android_app/app/src/main/java/com/health/openscale/gui/views/MeasurementView.java
@@ -382,7 +382,6 @@ public abstract class MeasurementView extends TableLayout {
             evalResult = new EvaluationResult();
         }
 
-        evaluatorView.setMinMaxValue(getMinValue(), getMaxValue());
         evaluatorView.setLimits(evalResult.lowLimit, evalResult.highLimit);
         evaluatorView.setValue(value);