extension: Make "System Monitor" action customizable

Some users would like to use a different system monitor other than the
current GNOME System Monitor app. Add a new setting that can be used to
specify a custom command for a system monitor app, falling back to the
default when none is provided (or on error).

Fixes #96

system-monitor-next@paradoxxx.zero.gmail.com/extension.js

@@ -2397,6 +2397,44 @@ const Icon = class SystemMonitor_Icon {
 }
 
 export default class SystemMonitorExtension extends Extension {
+    openSystemMonitor() {
+        let _appSys = Shell.AppSystem.get_default();
+        let _gsmApp = _appSys.lookup_app('org.gnome.SystemMonitor.desktop') || _appSys.lookup_app('gnome-system-monitor.desktop');
+        let customCmd = this._Schema.get_string('custom-monitor-command');
+
+        if (!customCmd || customCmd.trim() === '') {
+            _gsmApp.activate();
+            return;
+        }
+
+        sm_log("Executing custom system monitor command: " + customCmd);
+        try {
+            let [success, argv] = GLib.shell_parse_argv(customCmd);
+            if (!success) {
+                sm_log('Failed to parse custom monitor command: ' + customCmd, 'error');
+                _gsmApp.activate();
+                return;
+            }
+
+            let proc = new Gio.Subprocess({
+                argv: argv,
+                flags: Gio.SubprocessFlags.NONE
+            });
+            proc.init(null);
+            proc.wait_async(null, (proc, result) => {
+                try {
+                    proc.wait_finish(result);
+                    sm_log('Custom system monitor command completed with exit code: ' + proc.get_exit_status());
+                } catch (e) {
+                    sm_log('Error waiting for process completion: ' + e.message, 'error');
+                }
+            });
+        } catch (e) {
+            sm_log('Failed to execute custom monitor command: ' + e.message, 'error');
+            _gsmApp.activate();
+        }
+    }
+
     enable() {
         sm_log('applet enable from ' + this.path);
 
@@ -2526,13 +2564,10 @@ export default class SystemMonitorExtension extends Extension {
             }
         );
 
-        let _appSys = Shell.AppSystem.get_default();
-        let _gsmApp = _appSys.lookup_app('org.gnome.SystemMonitor.desktop') || _appSys.lookup_app('gnome-system-monitor.desktop');
-
         let item;
         item = new PopupMenu.PopupMenuItem(_('System Monitor...'));
         item.connect('activate', () => {
-            _gsmApp.activate();
+            this.openSystemMonitor();
         });
         tray.menu.addMenuItem(item);
 

system-monitor-next@paradoxxx.zero.gmail.com/prefs.js

@@ -40,7 +40,8 @@ const SMGeneralPrefsPage = GObject.registerClass({
     GTypeName: 'SMGeneralPrefsPage',
     Template: import.meta.url.replace('prefs.js', 'ui/prefsGeneralSettings.ui'),
     InternalChildren: ['background', 'icon_display', 'show_tooltip', 'move_clock',
-        'compact_display', 'center_display', 'rotate_labels', 'tooltip_delay_ms'],
+        'compact_display', 'center_display', 'rotate_labels', 'tooltip_delay_ms',
+        'custom_monitor_switch', 'custom_monitor_command'],
 }, class SMGeneralPrefsPage extends Adw.PreferencesPage {
     constructor(settings, params = {}) {
         super(params);
@@ -86,6 +87,21 @@ const SMGeneralPrefsPage = GObject.registerClass({
         this._settings.bind('tooltip-delay-ms', this._tooltip_delay_ms,
             'value', Gio.SettingsBindFlags.DEFAULT
         );
+
+        const hasCommand = this._settings.get_string('custom-monitor-command').trim() !== '';
+        this._custom_monitor_switch.active = hasCommand;
+        this._custom_monitor_command.visible = hasCommand;
+
+        this._custom_monitor_switch.connect('notify::active', () => {
+            this._custom_monitor_command.visible = this._custom_monitor_switch.active;
+            if (!this._custom_monitor_switch.active) {
+                this._settings.set_string('custom-monitor-command', '');
+            }
+        });
+
+        this._settings.bind('custom-monitor-command', this._custom_monitor_command,
+            'text', Gio.SettingsBindFlags.DEFAULT
+        );
     }
 });
 

system-monitor-next@paradoxxx.zero.gmail.com/schemas/org.gnome.shell.extensions.system-monitor-next-applet.v1.gschema.xml

@@ -513,5 +513,10 @@
       <default>9</default>
       <summary>Position in which to display the battery display</summary>
     </key>
+    <key name="custom-monitor-command" type="s">
+      <default>''</default>
+      <summary>Custom system monitor command</summary>
+      <description>When set, this command will be executed instead of launching GNOME System Monitor</description>
+    </key>
   </schema>
 </schemalist>

system-monitor-next@paradoxxx.zero.gmail.com/ui/prefsGeneralSettings.ui

@@ -64,6 +64,18 @@
             </property>
           </object>
         </child>
+        <child>
+          <object class="AdwSwitchRow" id="custom_monitor_switch">
+            <property name="title" translatable="yes">Custom System Monitor Command</property>
+            <property name="subtitle" translatable="yes">Use a custom command instead of GNOME System Monitor</property>
+          </object>
+        </child>
+        <child>
+          <object class="AdwEntryRow" id="custom_monitor_command">
+            <property name="title" translatable="yes">Command (e.g. 'missioncenter')</property>
+            <property name="tooltip-text" translatable="yes">Command to run instead of GNOME System Monitor</property>
+          </object>
+        </child>
       </object>
     </child>
   </template>