From 516520b775bc7f347d1abe8965f953fef0940e27 Mon Sep 17 00:00:00 2001
From: DoinLakeFlyer <don@thegagnes.com>
Date: Wed, 1 Jan 2020 20:53:15 -0800
Subject: [PATCH] Only trust gcs heading from plugin

---
 src/PositionManager/PositionManager.cpp | 18 +++++++++++-------
 src/PositionManager/PositionManager.h   | 13 +++++++------
 2 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/src/PositionManager/PositionManager.cpp b/src/PositionManager/PositionManager.cpp
index 7d5fab0d2..e866ed5ce 100644
--- a/src/PositionManager/PositionManager.cpp
+++ b/src/PositionManager/PositionManager.cpp
@@ -13,12 +13,6 @@
 
 QGCPositionManager::QGCPositionManager(QGCApplication* app, QGCToolbox* toolbox)
     : QGCTool           (app, toolbox)
-    , _updateInterval   (0)
-    , _gcsHeading       (NAN)
-    , _currentSource    (nullptr)
-    , _defaultSource    (nullptr)
-    , _nmeaSource       (nullptr)
-    , _simulatedSource  (nullptr)
 {
 
 }
@@ -34,6 +28,9 @@ void QGCPositionManager::setToolbox(QGCToolbox *toolbox)
    QGCTool::setToolbox(toolbox);
    //-- First see if plugin provides a position source
    _defaultSource = toolbox->corePlugin()->createPositionSource(this);
+   if (_defaultSource) {
+       _usingPluginSource = true;
+   }
 
    if (qgcApp()->runningUnitTests()) {
        // Units test on travis fail due to lack of position source
@@ -91,7 +88,14 @@ void QGCPositionManager::_positionUpdated(const QGeoPositionInfo &update)
         _gcsPosition = newGCSPosition;
         emit gcsPositionChanged(_gcsPosition);
     }
-    if (newGCSHeading != _gcsHeading) {
+
+    // At this point only plugins support gcs heading. The reason is that the quality of heading information from a local
+    // position device (not a compass) is unknown. In many cases it can only be trusted if the GCS location is moving above
+    // a certain rate of speed. When it is not, or the gcs is standing still the heading is just random. We don't want these
+    // random heading to be shown on the fly view. So until we can get a true compass based heading or some smarted heading quality
+    // information which takes into account the speed of movement we normally don't set a heading. We do use the heading though
+    // if the plugin overrides the position source. In that case we assume that it hopefully know what it is doing.
+    if (_usingPluginSource && newGCSHeading != _gcsHeading) {
         _gcsHeading = newGCSHeading;
         emit gcsHeadingChanged(_gcsHeading);
     }
diff --git a/src/PositionManager/PositionManager.h b/src/PositionManager/PositionManager.h
index 0f2d3a74c..a7e6b31ce 100644
--- a/src/PositionManager/PositionManager.h
+++ b/src/PositionManager/PositionManager.h
@@ -56,13 +56,14 @@ signals:
     void positionInfoUpdated(QGeoPositionInfo update);
 
 private:
-    int                 _updateInterval;
+    int                 _updateInterval =   0;
     QGeoPositionInfo    _geoPositionInfo;
     QGeoCoordinate      _gcsPosition;
-    qreal               _gcsHeading;
+    qreal               _gcsHeading =       qQNaN();
 
-    QGeoPositionInfoSource*     _currentSource;
-    QGeoPositionInfoSource*     _defaultSource;
-    QNmeaPositionInfoSource*    _nmeaSource;
-    QGeoPositionInfoSource*     _simulatedSource;
+    QGeoPositionInfoSource*     _currentSource =        nullptr;
+    QGeoPositionInfoSource*     _defaultSource =        nullptr;
+    QNmeaPositionInfoSource*    _nmeaSource =           nullptr;
+    QGeoPositionInfoSource*     _simulatedSource =      nullptr;
+    bool                        _usingPluginSource =    false;
 };
-- 
2.22.0