[chronojump] force sensor capture graph is ok now for really low forces

[Xavier de Blas <xaviblas src gnome org>]

commit f1ae151043603aa59388c95d1f9873f131f20daf
Author: Xavier de Blas <xaviblas gmail com>
Date:   Mon Sep 16 17:41:23 2019 +0200

    force sensor capture graph is ok now for really low forces

 src/forceSensor.cs     |  4 ++--
 src/gui/forceSensor.cs | 10 +++++++---
 2 files changed, 9 insertions(+), 5 deletions(-)
---
diff --git a/src/forceSensor.cs b/src/forceSensor.cs
index 00612baf..e5dc043c 100644
--- a/src/forceSensor.cs
+++ b/src/forceSensor.cs
@@ -311,8 +311,8 @@ public class ForceSensorCapturePoints
 
        public int RealWidthG; //width of graph in microseconds (will be upgraded if needed)
 
-       public const int DefaultRealHeightG = 20;
-       public const int DefaultRealHeightGNeg = 10;
+       public const int DefaultRealHeightG = 2;
+       public const int DefaultRealHeightGNeg = 2;
        public int RealHeightG; //Newtons (will be upgraded if needed)
        public int RealHeightGNeg; //Newtons (negative) (will be upgraded if needed)
 
diff --git a/src/gui/forceSensor.cs b/src/gui/forceSensor.cs
index b5e56b74..e02375e6 100644
--- a/src/gui/forceSensor.cs
+++ b/src/gui/forceSensor.cs
@@ -1717,9 +1717,13 @@ LogB.Information(" re R ");
 
        private void setForceSensorTopAtOperationStart()
        {
-               forceSensorTopRectangleAtOperationStart =
-                       Convert.ToInt32(spin_force_sensor_capture_feedback_at.Value +
-                                       spin_force_sensor_capture_feedback_range.Value /2);
+               int at = Convert.ToInt32(spin_force_sensor_capture_feedback_at.Value);
+               int range = Convert.ToInt32(spin_force_sensor_capture_feedback_range.Value);
+
+               if(at == 0 || range == 0)
+                       forceSensorTopRectangleAtOperationStart = 0;
+               else
+                       forceSensorTopRectangleAtOperationStart = Convert.ToInt32(at + range /2);
        }
        //This function calculates the max value between the sent force and the top of the feedback rectangle
        private int getForceSensorMaxForceIncludingRectangle(double forceValue)