Fix hang caused by no Notifications service registered in DBus

Issue #4353

Add a check when looking up the `org.freedesktop.Notifications` service
to see if the it actually exists before trying to fetch it

Add a check on QDBus service lookup in screengrabber freedesktop

Author: samwcoulter

data/translations/Internationalization_en.ts

@@ -502,6 +502,14 @@
         <translation type="unfinished"></translation>
     </message>
 </context>
+<context>
+    <name>SystemNotification</name>
+    <message>
+        <location filename="../../src/utils/systemnotification.cpp" line="49"/>
+        <source>No DBus System Notification service found</source>
+        <translation type="unfinished"></translation>
+    </message>
+</context>
 <context>
     <name>ConfigResolver</name>
     <message>
@@ -1779,27 +1787,32 @@ You may need to escape the &apos;#&apos; sign as in &apos;\#FFF&apos;</source>
         <translation type="unfinished"></translation>
     </message>
     <message>
-        <location filename="../../src/utils/screengrabber.cpp" line="171"/>
-        <source>If the useGrimAdapter setting is not enabled, the dbus protocol will be used. It should be noted that using the dbus protocol under wayland is not recommended. It is recommended to enable the useGrimAdapter setting in flameshot.ini to activate the grim-based general wayland screenshot adapter</source>
+        <location filename="../../src/utils/screengrabber.cpp" line="70"/>
+        <source>Could not locate the `org.freedesktop.portal.Desktop` service</source>
         <translation type="unfinished"></translation>
     </message>
     <message>
         <location filename="../../src/utils/screengrabber.cpp" line="182"/>
+        <source>If the useGrimAdapter setting is not enabled, the dbus protocol will be used. It should be noted that using the dbus protocol under wayland is not recommended. It is recommended to enable the useGrimAdapter setting in flameshot.ini to activate the grim-based general wayland screenshot adapter</source>
+        <translation type="unfinished"></translation>
+    </message>
+    <message>
+        <location filename="../../src/utils/screengrabber.cpp" line="193"/>
         <source>grim&apos;s screenshot component is implemented based on wlroots, it may not be used in GNOME or similar desktop environments</source>
         <translation type="unfinished"></translation>
     </message>
     <message>
-        <location filename="../../src/utils/screengrabber.cpp" line="194"/>
+        <location filename="../../src/utils/screengrabber.cpp" line="204"/>
         <source>Unable to detect desktop environment (GNOME? KDE? Qile? Sway? ...)</source>
         <translation type="unfinished"></translation>
     </message>
     <message>
-        <location filename="../../src/utils/screengrabber.cpp" line="197"/>
+        <location filename="../../src/utils/screengrabber.cpp" line="207"/>
         <source>Hint: try setting the XDG_CURRENT_DESKTOP environment variable.</source>
         <translation type="unfinished"></translation>
     </message>
     <message>
-        <location filename="../../src/utils/screengrabber.cpp" line="202"/>
+        <location filename="../../src/utils/screengrabber.cpp" line="212"/>
         <source>Unable to capture screen</source>
         <translation type="unfinished"></translation>
     </message>

src/utils/screengrabber.cpp

@@ -61,8 +61,18 @@ void ScreenGrabber::freeDesktopPortal(bool& ok, QPixmap& res)
 {
 
 #if !(defined(Q_OS_MACOS) || defined(Q_OS_WIN))
+    auto* connectionInterface = QDBusConnection::sessionBus().interface();
+    auto service = QStringLiteral("org.freedesktop.portal.Desktop");
+
+    if (!connectionInterface->isServiceRegistered(service)) {
+        ok = false;
+        AbstractLogger::error() << tr(
+          "Could not locate the `org.freedesktop.portal.Desktop` service");
+        return;
+    }
+
     QDBusInterface screenshotInterface(
-      QStringLiteral("org.freedesktop.portal.Desktop"),
+      service,
       QStringLiteral("/org/freedesktop/portal/desktop"),
       QStringLiteral("org.freedesktop.portal.Screenshot"));
 
@@ -72,7 +82,7 @@ void ScreenGrabber::freeDesktopPortal(bool& ok, QPixmap& res)
 
     // premake interface
     auto* request = new OrgFreedesktopPortalRequestInterface(
-      QStringLiteral("org.freedesktop.portal.Desktop"),
+      service,
       "/org/freedesktop/portal/desktop/request/" +
         QDBusConnection::sessionBus().baseService().remove(':').replace('.',
                                                                         '_') +

src/utils/systemnotification.cpp

@@ -1,11 +1,13 @@
 #include "systemnotification.h"
 #include "src/core/flameshot.h"
+#include "src/utils/abstractlogger.h"
 #include "src/utils/confighandler.h"
 #include <QApplication>
 #include <QUrl>
 
 #if !(defined(Q_OS_MACOS) || defined(Q_OS_WIN))
 #include <QDBusConnection>
+#include <QDBusConnectionInterface>
 #include <QDBusInterface>
 #include <QDBusMessage>
 #else
@@ -27,12 +29,20 @@ SystemNotification::SystemNotification(QObject* parent)
     if (!ConfigHandler().showDesktopNotification()) {
         return;
     }
-    m_interface =
-      new QDBusInterface(QStringLiteral("org.freedesktop.Notifications"),
-                         QStringLiteral("/org/freedesktop/Notifications"),
-                         QStringLiteral("org.freedesktop.Notifications"),
-                         QDBusConnection::sessionBus(),
-                         this);
+    auto bus = QDBusConnection::sessionBus();
+    auto* connectionInterface = bus.interface();
+
+    auto service = QStringLiteral("org.freedesktop.Notifications");
+    auto path = QStringLiteral("/org/freedesktop/Notifications");
+    auto interface = QStringLiteral("org.freedesktop.Notifications");
+
+    if (connectionInterface->isServiceRegistered(service)) {
+        m_interface = new QDBusInterface(service, path, interface, bus, this);
+    } else {
+        AbstractLogger::warning(AbstractLogger::Stderr |
+                                AbstractLogger::LogFile)
+          << tr("No DBus System Notification service found");
+    }
 #endif
 }
 
@@ -63,24 +73,26 @@ void SystemNotification::sendMessage(const QString& text,
       },
       Qt::QueuedConnection);
 #else
-    QList<QVariant> args;
-    QVariantMap hintsMap;
-    if (!savePath.isEmpty()) {
-        QUrl fullPath = QUrl::fromLocalFile(savePath);
-        // allows the notification to be dragged and dropped
-        hintsMap[QStringLiteral("x-kde-urls")] =
-          QStringList({ fullPath.toString() });
-    }
+    if (nullptr != m_interface && m_interface->isValid()) {
+        QList<QVariant> args;
+        QVariantMap hintsMap;
+        if (!savePath.isEmpty()) {
+            QUrl fullPath = QUrl::fromLocalFile(savePath);
+            // allows the notification to be dragged and dropped
+            hintsMap[QStringLiteral("x-kde-urls")] =
+              QStringList({ fullPath.toString() });
+        }
 
-    args << (qAppName())                 // appname
-         << static_cast<unsigned int>(0) // id
-         << FLAMESHOT_ICON               // icon
-         << title                        // summary
-         << text                         // body
-         << QStringList()                // actions
-         << hintsMap                     // hints
-         << timeout;                     // timeout
-    m_interface->callWithArgumentList(
-      QDBus::AutoDetect, QStringLiteral("Notify"), args);
+        args << (qAppName())                 // appname
+             << static_cast<unsigned int>(0) // id
+             << FLAMESHOT_ICON               // icon
+             << title                        // summary
+             << text                         // body
+             << QStringList()                // actions
+             << hintsMap                     // hints
+             << timeout;                     // timeout
+        m_interface->callWithArgumentList(
+          QDBus::AutoDetect, QStringLiteral("Notify"), args);
+    }
 #endif
 }