implement inhibiting sleep on linux during video playback

Fixes #1791

app/widget/viewer/viewerpreventsleep.cpp

@@ -6,12 +6,16 @@
 #include <winbase.h>
 #elif defined(Q_OS_MAC)
 #include <IOKit/pwr_mgt/IOPMLib.h>
+#elif defined(Q_OS_LINUX)
+#include <QtDBus/QtDBus>
 #endif
 
 namespace olive {
 
 #if defined(Q_OS_MAC)
 IOPMAssertionID assertionID = 0;
+#elif defined(Q_OS_LINUX)
+
 #endif
 
 void PreventSleep(bool on)
@@ -28,6 +32,42 @@ void PreventSleep(bool on)
     IOPMAssertionRelease(assertionID);
     assertionID = 0;
   }
+#elif defined(Q_OS_LINUX)
+  QDBusConnection bus = QDBusConnection::sessionBus();
+  if(bus.isConnected()) {
+    static const QStringList sleep_services = {
+      QStringLiteral("org.freedesktop.ScreenSaver"),
+      //QStringLiteral("org.gnome.SessionManager")
+    };
+    static const QStringList sleep_paths = {
+      QStringLiteral("/org/freedesktop/ScreenSaver"),
+      //QStringLiteral("/org/gnome/SessionManager")
+    };
+    static QVector<uint> sleep_cookies;
+
+    // Initialize vector to 0
+    if (sleep_cookies.isEmpty()) {
+      sleep_cookies.resize(sleep_services.size());
+      sleep_cookies.fill(0);
+    }
+
+    for (int i=0; i<sleep_cookies.size(); i++) {
+      QDBusInterface interface(sleep_services.at(i), sleep_paths.at(i), sleep_services.at(i), bus);
+      if (interface.isValid()) {
+        QDBusReply<uint> reply;
+
+        if (on) {
+          reply = interface.call(QStringLiteral("Inhibit"), QStringLiteral("Olive Video Editor"), QStringLiteral("Video Playback"));
+        } else {
+          reply = interface.call(QStringLiteral("UnInhibit"), sleep_cookies.at(i));
+        }
+
+        if (reply.isValid()) {
+          sleep_cookies[i] = reply.value();
+        }
+      }
+    }
+  }
 #endif
 }