Add support on MacOS to detect when the accessibility permission is removed

doc/newsfragments/mac-accessibility-permission.feature

@@ -0,0 +1 @@
++ Add support to detect when the accessibility permission has been removed on MacOS and terminate the application.

src/gui/CMakeLists.txt

@@ -21,6 +21,7 @@ set(GUI_COMMON_HEADER_FILES
 
 set(GUI_SOURCE_FILES
     src/AboutDialog.cpp
+    src/AccessibilityPermissionObserver.cpp
     src/ActionDialog.cpp
     src/AddClientDialog.cpp
     src/AppConfig.cpp
@@ -61,6 +62,7 @@ set(GUI_SOURCE_FILES
 
 set(GUI_HEADER_FILES
     src/AboutDialog.h
+    src/AccessibilityPermissionObserver.h
     src/ActionDialog.h
     src/AddClientDialog.h
     src/AppConfig.h

src/gui/src/AccessibilityPermissionObserver.cpp

@@ -0,0 +1,52 @@
+/*
+ * barrier -- mouse and keyboard sharing utility
+ * Copyright (C) 2022 Duncan Cunningham
+ *
+ * This package is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * found in the file LICENSE that should have accompanied this file.
+ *
+ * This package is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "AccessibilityPermissionObserver.h"
+
+#include <QApplication>
+#include <QTimer>
+
+#if defined(Q_OS_MAC)
+#include <Carbon/Carbon.h>
+#endif
+
+AccessibilityPermissionObserver::AccessibilityPermissionObserver(QObject* parent)
+    : QObject(parent)
+{
+#if __MAC_OS_X_VERSION_MIN_REQUIRED >= 1090 // mavericks
+    m_pTimer = new QTimer(this);
+
+    connect(m_pTimer, SIGNAL(timeout()), this, SLOT(checkAccessibilityPermissions()));
+#endif
+}
+
+void AccessibilityPermissionObserver::start()
+{
+    if (m_pTimer) {
+        m_pTimer->start(1000);
+    }
+}
+
+void AccessibilityPermissionObserver::checkAccessibilityPermissions()
+{
+#if __MAC_OS_X_VERSION_MIN_REQUIRED >= 1090 // mavericks
+    // There's no API to be notified when this permission changes, so we have to poll it.
+    if (!AXIsProcessTrusted()) {
+        QApplication::quit();
+    }
+#endif
+}

src/gui/src/AccessibilityPermissionObserver.h

@@ -0,0 +1,34 @@
+/*
+ * barrier -- mouse and keyboard sharing utility
+ * Copyright (C) 2022 Duncan Cunningham
+ *
+ * This package is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * found in the file LICENSE that should have accompanied this file.
+ *
+ * This package is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <QObject>
+
+class QTimer;
+
+class AccessibilityPermissionObserver: public QObject
+{
+    Q_OBJECT
+public:
+    explicit AccessibilityPermissionObserver(QObject* parent = nullptr);
+    void start();
+public slots:
+    void checkAccessibilityPermissions();
+private:
+    QTimer* m_pTimer;
+};

src/gui/src/MainWindow.cpp

@@ -21,6 +21,7 @@
 #include "MainWindow.h"
 
 #include "AboutDialog.h"
+#include "AccessibilityPermissionObserver.h"
 #include "ServerConfigDialog.h"
 #include "SettingsDialog.h"
 #include "ZeroconfService.h"
@@ -118,7 +119,8 @@ MainWindow::MainWindow(QSettings& settings, AppConfig& appConfig) :
     m_SuppressEmptyServerWarning(false),
     m_ExpectedRunningState(kStopped),
     m_pSslCertificate(NULL),
-    m_pLogWindow(new LogWindow(nullptr))
+    m_pLogWindow(new LogWindow(nullptr)),
+    m_pAccessibilityPermissionObserver(nullptr)
 {
     // explicitly unset DeleteOnClose so the window can be show and hidden
     // repeatedly until Barrier is finished
@@ -503,6 +505,11 @@ void MainWindow::startBarrier()
     bool desktopMode = appConfig().processMode() == Desktop;
     bool serviceMode = appConfig().processMode() == Service;
 
+#if defined(Q_OS_MAC)
+    m_pAccessibilityPermissionObserver = new AccessibilityPermissionObserver(this);
+    m_pAccessibilityPermissionObserver->start();
+#endif
+
     appendLogDebug("starting process");
     m_ExpectedRunningState = kStarted;
     setBarrierState(barrierConnecting);
@@ -767,6 +774,11 @@ void MainWindow::stopBarrier()
 
     // reset so that new connects cause auto-hide.
     m_AlreadyHidden = false;
+
+#if defined(Q_OS_MAC)
+    delete m_pAccessibilityPermissionObserver;
+    m_pAccessibilityPermissionObserver = nullptr;
+#endif
 }
 
 void MainWindow::stopService()

src/gui/src/MainWindow.h

@@ -53,6 +53,7 @@ class QTemporaryFile;
 class QMessageBox;
 class QAbstractButton;
 
+class AccessibilityPermissionObserver;
 class LogDialog;
 class QBarrierApplication;
 class SetupWizard;
@@ -198,6 +199,7 @@ public slots:
         SslCertificate* m_pSslCertificate;
         QStringList m_PendingClientNames;
         LogWindow *m_pLogWindow;
+        AccessibilityPermissionObserver* m_pAccessibilityPermissionObserver;
 
         bool m_fingerprint_expanded = false;