backend: Persist use-server setting

backend/src/lib.rs

@@ -118,6 +118,8 @@ impl Backend {
             _ => (),
         }
 
+        self.use_server.set(self.settings.boolean("use-server"));
+
         if self.get_music_library_path().is_none() {
             self.set_state(BackendState::NoMusicLibrary);
         } else {
@@ -128,13 +130,24 @@ impl Backend {
     }
 
     /// Whether the server should be used by default.
+    ///
+    /// This will return `false` if no server URL is set up. Otherwise, the
+    /// value is based on the users "use-server" preference.
     pub fn use_server(&self) -> bool {
-        self.use_server.get()
+        self.client.get_server_url().is_some() && self.use_server.get()
     }
 
     /// Set whether the server should be used by default.
     pub fn set_use_server(&self, enabled: bool) {
         self.use_server.set(enabled);
+
+        if let Err(err) = self.settings.set_boolean("use-server", enabled) {
+            warn!(
+                "An error happened whilte trying to save the \"use-server\" setting to GSettings. \
+                Error message: {}",
+                err
+            )
+        }
     }
 
     /// Set the URL of the Musicus server to connect to.

musicus/data/de.johrpan.musicus.gschema.xml

@@ -9,5 +9,13 @@
 			<default>"https://wolfgang.johrpan.de"</default>
 			<summary>URL of the Wolfgang server to use</summary>
 		</key>
+		<key name="use-server" type="b">
+			<default>true</default>
+			<summary>Whether to use the Wolfgang server</summary>
+			<description>
+				This setting determines whether the Wolfgang server will be used for
+				finding new items as well as to upload new additions and edits.
+			</description>
+		</key>
 	</schema>
 </schemalist>