Geary.State.Machine: Support GObject notify signal for state changes

Modernise the API a bit by using properties instead of explicit
getters/setters, an hence support GObject notify signals when the
state property changes.

src/engine/imap/transport/imap-client-session.vala

@@ -483,11 +483,10 @@ public class Geary.Imap.ClientSession : BaseObject, Logging.Source {
         };
 
         fsm = new Geary.State.Machine(machine_desc, mappings, on_ignored_transition);
-        fsm.set_logging(false);
     }
 
     ~ClientSession() {
-        switch (fsm.get_state()) {
+        switch (fsm.state) {
             case State.NOT_CONNECTED:
             case State.CLOSED:
                 // no problem-o
@@ -782,7 +781,7 @@ public class Geary.Imap.ClientSession : BaseObject, Logging.Source {
 
     private bool on_greeting_timeout() {
         // if still in CONNECTING state, the greeting never arrived
-        if (fsm.get_state() == State.CONNECTING)
+        if (fsm.state == State.CONNECTING)
             fsm.issue(Event.TIMEOUT);
 
         return false;
@@ -1645,12 +1644,12 @@ public class Geary.Imap.ClientSession : BaseObject, Logging.Source {
         return (this.selected_mailbox == null)
             ? new Logging.State(
                 this,
-                this.fsm.get_state_string(fsm.get_state())
+                this.fsm.get_state_string(fsm.state)
             )
             : new Logging.State(
                 this,
                 "%s:%s selected %s",
-                this.fsm.get_state_string(fsm.get_state()),
+                this.fsm.get_state_string(fsm.state),
                 this.selected_mailbox.to_string(),
                 this.selected_readonly ? "RO" : "RW"
             );

src/engine/imap/transport/imap-deserializer.vala

@@ -294,7 +294,7 @@ public class Geary.Imap.Deserializer : BaseObject, Logging.Source {
 
     /** {@inheritDoc} */
     public Logging.State to_logging_state() {
-        return new Logging.State(this, fsm.get_state_string(fsm.get_state()));
+        return new Logging.State(this, fsm.get_state_string(fsm.state));
     }
 
     /** Sets the connection's logging parent. */
@@ -429,7 +429,7 @@ public class Geary.Imap.Deserializer : BaseObject, Logging.Source {
     }
 
     private Mode get_mode() {
-        switch (fsm.get_state()) {
+        switch (fsm.state) {
             case State.LITERAL_DATA:
                 return Mode.BLOCK;
 

src/engine/state/state-machine.vala

@@ -5,13 +5,20 @@
  */
 
 public class Geary.State.Machine : BaseObject {
+
+    /** The state machine's current state. */
+    public uint state { get; private set; }
+
+    /** Determines if the state machine crashes your app when mis-configured. */
+    public bool abort_on_no_transition { get; set; default = true; }
+
+    /** Determines if transition logging is enabled. */
+    public bool logging { get; private set; default = false; }
+
     private Geary.State.MachineDescriptor descriptor;
-    private uint state;
     private Mapping[,] transitions;
     private unowned Transition? default_transition;
     private bool locked = false;
-    private bool abort_on_no_transition = true;
-    private bool logging = false;
     private unowned PostTransition? post_transition = null;
     private void *post_user = null;
     private Object? post_object = null;
@@ -39,26 +46,6 @@ public class Geary.State.Machine : BaseObject {
         }
     }
 
-    public uint get_state() {
-        return state;
-    }
-
-    public bool get_abort_on_no_transition() {
-        return abort_on_no_transition;
-    }
-
-    public void set_abort_on_no_transition(bool abort) {
-        abort_on_no_transition = abort;
-    }
-
-    public void set_logging(bool logging) {
-        this.logging = logging;
-    }
-
-    public bool is_logging() {
-        return logging;
-    }
-
     public uint issue(uint event, void *user = null, Object? object = null, Error? err = null) {
         assert(event < descriptor.event_count);
         assert(state < descriptor.state_count);
@@ -70,7 +57,7 @@ public class Geary.State.Machine : BaseObject {
             string msg = "%s: No transition defined for %s@%s".printf(to_string(),
                 descriptor.get_event_string(event), descriptor.get_state_string(state));
 
-            if (get_abort_on_no_transition())
+            if (this.abort_on_no_transition)
                 error(msg);
             else
                 critical(msg);
@@ -96,7 +83,7 @@ public class Geary.State.Machine : BaseObject {
         }
         locked = false;
 
-        if (is_logging())
+        if (this.logging)
             message("%s: %s", to_string(), get_transition_string(old_state, event, state));
 
         // Perform post-transition if registered