UI: fix app opening from macOS dock

A single click on the app icon on macOS dock should
open the app.

Change-Id: Ied215ee9288d6d46fd8852a7daa996db7ac0468f

src/MainApplicationWindow.qml

@@ -150,6 +150,9 @@ ApplicationWindow {
                 // layoutManager to handle as much as possible.
                 layoutManager.restoreWindowSettings()
             }
+            if (Qt.platform.os.toString() === "osx") {
+                MainApplication.setEventFilter()
+            }
 
             // This will trigger `visible = true`.
             windowSettingsLoaded = true

src/mainapplication.cpp

@@ -445,3 +445,11 @@ MainApplication::cleanup()
 #endif
     QApplication::exit(0);
 }
+
+#ifdef Q_OS_MACOS
+void
+MainApplication::setEventFilter()
+{
+    installEventFilter(this);
+}
+#endif

src/mainapplication.h

@@ -83,6 +83,18 @@ public:
         return runOptions_[opt];
     };
 
+#ifdef Q_OS_MACOS
+    Q_INVOKABLE void setEventFilter();
+
+    bool eventFilter(QObject* object, QEvent* event)
+    {
+        if (event->type() == QEvent::ApplicationActivate) {
+            restoreApp();
+        }
+        return QApplication::eventFilter(object, event);
+    }
+#endif // Q_OS_MACOS
+
 Q_SIGNALS:
     void closeRequested();