[geary/mjog/invert-folder-class-hierarchy] engine: Add RemoteFolder.is_connected property

[Michael Gratton <mjog src gnome org>]

commit 51da5e82323512dbba3a5e6cd817e2011a2df125
Author: Michael Gratton <mike vee net>
Date:   Thu Mar 4 21:20:23 2021 +1100

    engine: Add RemoteFolder.is_connected property

 src/engine/api/geary-remote-folder.vala                | 10 ++++++++++
 src/engine/imap-engine/imap-engine-minimal-folder.vala |  7 +++++++
 test/mock/mock-remote-folder.vala                      |  5 +++++
 3 files changed, 22 insertions(+)
---
diff --git a/src/engine/api/geary-remote-folder.vala b/src/engine/api/geary-remote-folder.vala
index b58485ade..87ea594dc 100644
--- a/src/engine/api/geary-remote-folder.vala
+++ b/src/engine/api/geary-remote-folder.vala
@@ -91,6 +91,16 @@ public interface Geary.RemoteFolder : Folder {
     }
 
 
+    /**
+     * Determines if there is an open network connection to the remote.
+     *
+     * Note that this property reflects the engine's best current
+     * understanding of whether a remote connection is currently
+     * available. It may be inaccurate due to changing network
+     * conditions and is at best treated as advisory.
+     */
+    public abstract bool is_connected { get; }
+
     /**
      * Last known properties of this folder's remote mailbox.
      *
diff --git a/src/engine/imap-engine/imap-engine-minimal-folder.vala 
b/src/engine/imap-engine/imap-engine-minimal-folder.vala
index 30d649ccf..d599d43da 100644
--- a/src/engine/imap-engine/imap-engine-minimal-folder.vala
+++ b/src/engine/imap-engine/imap-engine-minimal-folder.vala
@@ -78,6 +78,11 @@ private class Geary.ImapEngine.MinimalFolder : BaseObject,
         get { return this.local_folder.properties; }
     }
 
+    /** {@inheritDoc} */
+    public bool is_connected {
+        get { return this.remote_session != null; }
+    }
+
     /** {@inheritDoc} */
     public bool is_fully_expanded {
         get { return this._is_fully_expanded; }
@@ -455,6 +460,7 @@ private class Geary.ImapEngine.MinimalFolder : BaseObject,
         // All done, can now hook up the session to the folder
         this.remote_session = session;
         session.disconnected.connect(on_remote_disconnected);
+        notify_property("is-connected");
 
         // Enable IDLE now that the local and remote folders are in
         // sync. Can't do this earlier since we might get untagged
@@ -824,6 +830,7 @@ private class Geary.ImapEngine.MinimalFolder : BaseObject,
                 this.update_flags_timer.reset();
                 this.replay_queue.stop_remote();
                 this.remote_session = null;
+                notify_property("is-connected");
 
                 session.appended.disconnect(on_remote_appended);
                 session.updated.disconnect(on_remote_updated);
diff --git a/test/mock/mock-remote-folder.vala b/test/mock/mock-remote-folder.vala
index 08907fd55..1be3865b8 100644
--- a/test/mock/mock-remote-folder.vala
+++ b/test/mock/mock-remote-folder.vala
@@ -63,6 +63,11 @@ public class Mock.RemoteFolder : GLib.Object,
         get { return this._used_as; }
     }
 
+    public bool is_connected {
+        get { return this._connected; }
+    }
+    private bool _connected = false;
+
     public bool is_fully_expanded {
         get { return this._is_fully_expanded; }
     }