From 2be7a2c86edf2d286cdda3b3d7f520b8949cc0f8 Mon Sep 17 00:00:00 2001
From: Michel Dagenais <michel.dagenais@polymtl.ca>
Date: Thu, 18 Mar 2021 22:22:09 -0400
Subject: [PATCH] Compute the altitude incrementally from slope for Manual
 Slope Mode (#3847)

---
 src/Train/TrainSidebar.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/Train/TrainSidebar.cpp b/src/Train/TrainSidebar.cpp
index bad29536c..339e272c3 100644
--- a/src/Train/TrainSidebar.cpp
+++ b/src/Train/TrainSidebar.cpp
@@ -1788,6 +1788,13 @@ void TrainSidebar::guiUpdate()           // refreshes the telemetry
                         rtData.setAltitude(displayAltitude);
                     }
                 }
+                else if (!(status & RT_MODE_ERGO)) {
+                    // For manual slope mode, estimate vertical change based upon time passed and slope.
+                    // Note this isn't exactly right but is very close - we should use the previous slope for the time passed.
+                    double altitudeDeltaMeters = slope * (10 * distanceTick); // ((slope / 100) * distanceTick) * 1000
+                    displayAltitude += altitudeDeltaMeters;
+                    rtData.setAltitude(displayAltitude);
+                }
 
                 // time
                 total_msecs = session_elapsed_msec + session_time.elapsed();