Fix single instance socket path for compatibility with flatpak

Telegram/SourceFiles/platform/linux/specific_linux.cpp

@@ -95,6 +95,13 @@ void SetApplicationIcon(const QIcon &icon) {
 	QApplication::setWindowIcon(icon);
 }
 
+bool InSandbox() {
+	static const auto Sandbox = QFileInfo::exists(
+		QStandardPaths::writableLocation(QStandardPaths::RuntimeLocation)
+		+ qsl("/flatpak-info"));
+	return Sandbox;
+}
+
 QString CurrentExecutablePath(int argc, char *argv[]) {
 	constexpr auto kMaxPath = 1024;
 	char result[kMaxPath] = { 0 };
@@ -112,6 +119,23 @@ QString CurrentExecutablePath(int argc, char *argv[]) {
 	return argc ? QFile::decodeName(argv[0]) : QString();
 }
 
+QString SingleInstanceLocalServerName(const QString &hash) {
+	const auto runtimeDir = QStandardPaths::writableLocation(
+		QStandardPaths::RuntimeLocation);
+
+	if (InSandbox()) {
+		return runtimeDir
+			+ qsl("/app/")
+			+ QString::fromUtf8(qgetenv("FLATPAK_ID"))
+			+ '/' + hash;
+	} else if (QFileInfo::exists(runtimeDir)) {
+		return runtimeDir + '/' + hash + '-' + cGUIDStr();
+	} else { // non-systemd distros
+		return QStandardPaths::writableLocation(QStandardPaths::TempLocation)
+			+ '/' + hash + '-' + cGUIDStr();
+	}
+}
+
 } // namespace Platform
 
 namespace {