Flight display: Fix visuals, hide states that should not be operated, make sliders safer and allow to reduce altitude when in air

src/FlightDisplay/FlightDisplayViewWidgets.qml

@@ -446,12 +446,13 @@ Item {
 
                 QGCButton {
                     text:       (_activeVehicle && _activeVehicle.armed) ? (_activeVehicle.flying ? qsTr("Emergency Stop") : qsTr("Disarm")) :  qsTr("Arm")
+                    visible: (_activeVehicle && _activeVehicle.homePositionAvailable)
                     onClicked:  _guidedModeBar.confirmAction(_activeVehicle.armed ? (_activeVehicle.flying ? _guidedModeBar.confirmEmergencyStop : _guidedModeBar.confirmDisarm) : _guidedModeBar.confirmArm)
                 }
 
                 QGCButton {
                     text:       qsTr("RTL")
-                    visible:    _activeVehicle && _activeVehicle.guidedModeSupported && _activeVehicle.flying
+                    visible:    (_activeVehicle && _activeVehicle.armed) && _activeVehicle.guidedModeSupported && _activeVehicle.flying
                     onClicked:  _guidedModeBar.confirmAction(_guidedModeBar.confirmHome)
                 }
 
@@ -463,7 +464,7 @@ Item {
 
                 QGCButton {
                     text:       qsTr("Pause")
-                    visible:    _activeVehicle && _activeVehicle.pauseVehicleSupported && _activeVehicle.flying
+                    visible:    (_activeVehicle && _activeVehicle.armed) && _activeVehicle.pauseVehicleSupported && _activeVehicle.flying
                     onClicked:  {
                         guidedModeHideTimer.restart()
                         _activeVehicle.pauseVehicle()
@@ -472,7 +473,7 @@ Item {
 
                 QGCButton {
                     text:       qsTr("Change Altitude")
-                    visible:    _activeVehicle && _activeVehicle.guidedModeSupported && _activeVehicle.armed
+                    visible:    (_activeVehicle && _activeVehicle.flying) && _activeVehicle.guidedModeSupported && _activeVehicle.armed
                     onClicked:  _guidedModeBar.confirmAction(_guidedModeBar.confirmChangeAlt)
                 }
             } // Row
@@ -576,8 +577,8 @@ Item {
             anchors.left:       parent.left
             anchors.right:      parent.right
             orientation:        Qt.Vertical
-            minimumValue:       0
-            maximumValue:       QGroundControl.metersToAppSettingsDistanceUnits(100)
+            minimumValue:       QGroundControl.metersToAppSettingsDistanceUnits((_activeVehicle && _activeVehicle.flying) ? -15 : 0)
+            maximumValue:       QGroundControl.metersToAppSettingsDistanceUnits((_activeVehicle && _activeVehicle.flying) ? 15 : 60)
         }
     }
 }