Improve comments in Autopilot

Issue: https://denyspopov.atlassian.net/browse/AZ-14
Type: Improvement

src/az_drone_controller.h

@@ -1,7 +1,6 @@
 #pragma once
 
 #include <QObject>
-
 #include <memory.h>
 
 #include <mavsdk/mavsdk.h>
@@ -13,7 +12,7 @@
 
 using namespace mavsdk;
 
-typedef enum  {
+typedef enum {
     AZ_DRONE_STATE_DISCONNECTED,
     AZ_DRONE_STATE_CONNECTED,
     AZ_DRONE_STATE_AUTOPILOT,
@@ -32,7 +31,11 @@ class AzDroneController : public QObject
     Q_OBJECT
 public:
     explicit AzDroneController(AzMission &mission, QObject *parent = nullptr);
+
+    // Starts the autopilot.
     void start();
+
+    // Specify the methods that will be called one at a time to initialise the drone and fly the mission.
     bool stateConnect(void);
     bool stateAutopilot(void);
     bool stateTelemetryModule(void);
@@ -42,15 +45,32 @@ public:
     bool stateTakeoff(void);
     bool stateFlyMission(void);
 
+    // Slots that are called by the emitted Qt signals.
 private slots:
+    // Launches a state machine that progressively initialises the drone without blocking.
     void droneStateMachineSlot(void);
+
+    // ArduPilot seems to require some delay between calls. This method uses QTimer internally
+    // to call each new state method with some delay without blocking the main thread.
     void delayedStateCallSlot(int ms);
+
+    // Slot that is called when the newPosition() signal below is emitted.
     void newPositionSlot(Telemetry::Position);
+
+    // A mission file contains several action points. This is called
+    // when the action point is reached. Indexing starts at 1.
     void missionIndexChangedSlot(int currentIndex, int totalIndexes);
+
+    // Called at the end of the mission. Lands and disarms the drone.
     void missionFinishedSlot(void);
+
+    // Disarms the drone and exits the application. TODO!! Discuss quitting the application.
     void disarmDroneSlot(void);
 
 signals:
+    // Signal is emitted when Ardupilot sends a new position from the
+    // MAVSDK thread. Signal goes through the main event loop and is
+    // captured in the main thread to avoid threading issues.
     void newPosition(Telemetry::Position);
 
 private: