Fix drag visual glitches

src/FlightMap/MapItems/MissionItemIndicatorDrag.qml

@@ -29,6 +29,8 @@ Rectangle {
     property var itemCoordinate ///< Coordinate we are updating during drag
 
     signal clicked
+    signal dragStart
+    signal dragStop
 
     property bool   _preventCoordinateBindingLoop:  false
 
@@ -37,6 +39,7 @@ Rectangle {
     property real _touchHeight:             Math.max(itemIndicator.height, ScreenTools.minTouchPixels)
     property real _touchMarginHorizontal:   _mobile ? (_touchWidth - itemIndicator.width) / 2 : 0
     property real _touchMarginVertical:     _mobile ? (_touchHeight - itemIndicator.height) / 2 : 0
+    property bool _dragStartSignalled:      false
 
     onXChanged: liveDrag()
     onYChanged: liveDrag()
@@ -65,13 +68,18 @@ Rectangle {
         preventStealing:    true
 
         onClicked: itemDragger.clicked()
-    }
-
-    Item {
-        id: fakeItemIndicator
 
-        Item {
-            id: anchorPoint
+        property bool dragActive: drag.active
+        onDragActiveChanged: {
+            if (dragActive) {
+                if (!_dragStartSignalled) {
+                    _dragStartSignalled = true
+                    dragStart()
+                }
+            } else {
+                _dragStartSignalled = false
+                dragStop()
+            }
         }
     }
 }

src/MissionManager/QGCMapPolygon.cc

@@ -22,6 +22,7 @@ QGCMapPolygon::QGCMapPolygon(QObject* newCoordParent, QObject* parent)
     : QObject(parent)
     , _newCoordParent(newCoordParent)
     , _dirty(false)
+    , _centerDrag(false)
     , _ignoreCenterUpdates(false)
 {
     connect(&_polygonModel, &QmlObjectListModel::dirtyChanged, this, &QGCMapPolygon::_polygonModelDirtyChanged);
@@ -53,7 +54,10 @@ void QGCMapPolygon::clear(void)
 void QGCMapPolygon::adjustVertex(int vertexIndex, const QGeoCoordinate coordinate)
 {
     _polygonPath[vertexIndex] = QVariant::fromValue(coordinate);
-    emit pathChanged();
+    if (!_centerDrag) {
+        // When dragging center we don't signal path changed until add vertices are updated
+        emit pathChanged();
+    }
 
     _polygonModel.value<QGCQGeoCoordinate*>(vertexIndex)->setCoordinate(coordinate);
 
@@ -278,7 +282,22 @@ void QGCMapPolygon::setCenter(QGeoCoordinate newCenter)
             adjustVertex(i, newVertex);
         }
 
+        if (_centerDrag) {
+            // When center dragging signals are delayed until all vertices are updated
+            emit pathChanged();
+        }
+
         _ignoreCenterUpdates = false;
-        _updateCenter();
+
+        _center = newCenter;
+        emit centerChanged(newCenter);
+    }
+}
+
+void QGCMapPolygon::setCenterDrag(bool centerDrag)
+{
+    if (centerDrag != _centerDrag) {
+        _centerDrag = centerDrag;
+        emit centerDragChanged(centerDrag);
     }
 }

src/MissionManager/QGCMapPolygon.h

@@ -26,11 +26,12 @@ class QGCMapPolygon : public QObject
 public:
     QGCMapPolygon(QObject* newCoordParent, QObject* parent = NULL);
 
-    Q_PROPERTY(int                  count       READ count                          NOTIFY countChanged)
-    Q_PROPERTY(QVariantList         path        READ path                           NOTIFY pathChanged)
-    Q_PROPERTY(QmlObjectListModel*  pathModel   READ qmlPathModel                   CONSTANT)
-    Q_PROPERTY(bool                 dirty       READ dirty          WRITE setDirty  NOTIFY dirtyChanged)
-    Q_PROPERTY(QGeoCoordinate       center      READ center         WRITE setCenter NOTIFY centerChanged)
+    Q_PROPERTY(int                  count       READ count                              NOTIFY countChanged)
+    Q_PROPERTY(QVariantList         path        READ path                               NOTIFY pathChanged)
+    Q_PROPERTY(QmlObjectListModel*  pathModel   READ qmlPathModel                       CONSTANT)
+    Q_PROPERTY(bool                 dirty       READ dirty          WRITE setDirty      NOTIFY dirtyChanged)
+    Q_PROPERTY(QGeoCoordinate       center      READ center         WRITE setCenter     NOTIFY centerChanged)
+    Q_PROPERTY(bool                 centerDrag  READ centerDrag     WRITE setCenterDrag NOTIFY centerDragChanged)
 
     Q_INVOKABLE void clear(void);
     Q_INVOKABLE void appendVertex(const QGeoCoordinate& coordinate);
@@ -63,28 +64,30 @@ public:
 
     // Property methods
 
-    int             count   (void) const { return _polygonPath.count(); }
-    bool            dirty   (void) const { return _dirty; }
-    void            setDirty(bool dirty);
-    QGeoCoordinate  center  (void) const { return _center; }
-
+    int             count       (void) const { return _polygonPath.count(); }
+    bool            dirty       (void) const { return _dirty; }
+    void            setDirty    (bool dirty);
+    QGeoCoordinate  center      (void) const { return _center; }
+    bool            centerDrag  (void) const { return _centerDrag; }
 
     QVariantList        path        (void) const { return _polygonPath; }
     QmlObjectListModel* qmlPathModel(void) { return &_polygonModel; }
     QmlObjectListModel& pathModel   (void) { return _polygonModel; }
 
-    void setPath(const QList<QGeoCoordinate>& path);
-    void setPath(const QVariantList& path);
-    void setCenter(QGeoCoordinate newCenter);
+    void setPath        (const QList<QGeoCoordinate>& path);
+    void setPath        (const QVariantList& path);
+    void setCenter      (QGeoCoordinate newCenter);
+    void setCenterDrag  (bool centerDrag);
 
     static const char* jsonPolygonKey;
 
 signals:
-    void countChanged   (int count);
-    void pathChanged    (void);
-    void dirtyChanged   (bool dirty);
-    void cleared        (void);
-    void centerChanged  (QGeoCoordinate center);
+    void countChanged       (int count);
+    void pathChanged        (void);
+    void dirtyChanged       (bool dirty);
+    void cleared            (void);
+    void centerChanged      (QGeoCoordinate center);
+    void centerDragChanged  (bool centerDrag);
 
 private slots:
     void _polygonModelCountChanged(int count);
@@ -101,6 +104,7 @@ private:
     QmlObjectListModel  _polygonModel;
     bool                _dirty;
     QGeoCoordinate      _center;
+    bool                _centerDrag;
     bool                _ignoreCenterUpdates;
 };
 

src/MissionManager/QGCMapPolygonVisuals.qml

@@ -222,7 +222,9 @@ Item {
         id: centerDragAreaComponent
 
         MissionItemIndicatorDrag {
-            onItemCoordinateChanged: mapPolygon.center = itemCoordinate
+            onItemCoordinateChanged:    mapPolygon.center = itemCoordinate
+            onDragStart:                mapPolygon.centerDrag = true
+            onDragStop:                 mapPolygon.centerDrag = false
         }
     }