Draft: Check for long paths when not enabled on Windows

TODO: changelog entry

Fixes: #10264

Author: erikjv

src/common/utility.h

@@ -272,7 +272,7 @@ OCSYNC_EXPORT Q_DECLARE_LOGGING_CATEGORY(lcUtility)
     {
     public:
         /**
-         * NTFS permissions lookup is diabled by default for performance reasons
+         * NTFS permissions lookup is disabled by default for performance reasons
          * Enable it and disable it again once we leave the scope
          * https://doc.qt.io/Qt-5/qfileinfo.html#ntfs-permissions
          */

src/gui/folder.cpp

@@ -197,6 +197,17 @@ Folder::~Folder()
     _engine.reset();
 }
 
+static QString firstLongPathComponent(const QString &path, int size)
+{
+    for (const auto & component : path.split(QLatin1Char('/'))) {
+        if (component.size() >= size) {
+            return component;
+        }
+    }
+
+    return {};
+}
+
 bool Folder::checkLocalPath()
 {
 #ifdef Q_OS_WIN
@@ -217,9 +228,23 @@ bool Folder::checkLocalPath()
 
     QString error;
     if (fi.isDir() && fi.isReadable() && fi.isWritable()) {
-        qCDebug(lcFolder) << "Checked local path ok";
-        if (!_journal.open()) {
-            error = tr("%1 failed to open the database.").arg(_definition.localPath());
+        if (Utility::isWindows()) {
+            QString longPathComponent = firstLongPathComponent(_canonicalLocalPath, MAX_PATH);
+            if (!longPathComponent.isEmpty()) {
+                QSettings fsSettings(QStringLiteral("HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Control\\FileSystem"), QSettings::NativeFormat);
+                QVariant longPathsEnabled = fsSettings.value(QStringLiteral("LongPathsEnabled"));
+                qCDebug(lcFolder) << "LongPathsEnabled:" << longPathsEnabled;
+                if (longPathsEnabled.value<uint32_t>() != 1) {
+                    error = tr("The path component '%1' is too long. Either enable long paths in the Windows settings, or choose a different folder.").arg(longPathComponent);
+                }
+            }
+        }
+
+        if (error.isEmpty()) {
+            qCDebug(lcFolder) << "Checked local path ok";
+            if (!_journal.open()) {
+                error = tr("%1 failed to open the database.").arg(_definition.localPath());
+            }
         }
     } else {
         // Check directory again