mainview: add standard quit shortcut

Also rename 'Exit' to 'Quit' in the tray icon context menu for
non-Windows platforms for more standard/consistent terminology.

Change-Id: Id39bd308f17e56466ffb6b9c4929789646334b5e

src/mainapplication.cpp

@@ -479,11 +479,16 @@ MainApplication::initSystray()
 
     QMenu* systrayMenu = new QMenu();
 
-    QAction* exitAction = new QAction(tr("Exit"), this);
-    connect(exitAction, &QAction::triggered, [this] {
-        engine_->quit();
-        cleanup();
-    });
+    QString quitString;
+#ifdef Q_OS_WINDOWS
+    quitString = tr("E&xit");
+#else
+    quitString = tr("&Quit");
+#endif
+
+    QAction* quitAction = new QAction(quitString, this);
+    connect(quitAction, &QAction::triggered, this, &MainApplication::cleanup);
+
     connect(systemTray_.get(),
             &QSystemTrayIcon::activated,
             [this](QSystemTrayIcon::ActivationReason reason) {
@@ -491,7 +496,7 @@ MainApplication::initSystray()
                     restoreApp();
             });
 
-    systrayMenu->addAction(exitAction);
+    systrayMenu->addAction(quitAction);
     systemTray_->setContextMenu(systrayMenu);
     systemTray_->show();
 }

src/mainview/MainView.qml

@@ -612,6 +612,12 @@ Rectangle {
         }
     }
 
+    Shortcut {
+        sequence: StandardKey.Quit
+        context: Qt.ApplicationShortcut
+        onActivated: Qt.quit()
+    }
+
     KeyBoardShortcutTable {
         id: shortcutsTable
     }

src/settingsview/components/KeyBoardShortcutTable.qml

@@ -77,6 +77,12 @@ BaseDialog {
                 Description: qsTr("Fullscreen")
                 KeyLength: 1
             }
+            // TODO: add the following after redesign
+            // ListElement {
+            //     Shortcut: Qt.platform.os !== "windows" ? "Ctrl+Q" : "Alt+F4"
+            //     Description: Qt.platform.os !== "windows" ? qsTr("Quit") : qsTr("Exit")
+            //     KeyLength: 2
+            // }
         }
         ListModel {
             id: keyboardConversationShortcutsModel