QFileSystemEntry: Export static helper function checking for the root path

This provides a helper function which does the check on the string.
QFileInfo::isRoot() in addition checks for the existence of
the directory, which can cause hangs with network drives.
Use the new function in appropriate places in QtWidgets.

Task-number: QTBUG-6039
Change-Id: I54d0d860713e82b28fa4069a5345b042337f9c52
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/corelib/io/qfilesystementry.cpp

@@ -297,23 +297,27 @@ bool QFileSystemEntry::isAbsolute() const
 bool QFileSystemEntry::isDriveRoot() const
 {
     resolveFilePath();
+    return QFileSystemEntry::isDriveRootPath(m_filePath);
+}
+
+bool QFileSystemEntry::isDriveRootPath(const QString &path)
+{
 #ifndef Q_OS_WINRT
-    return (m_filePath.length() == 3
-           && m_filePath.at(0).isLetter() && m_filePath.at(1) == QLatin1Char(':')
-           && m_filePath.at(2) == QLatin1Char('/'));
+    return (path.length() == 3
+           && path.at(0).isLetter() && path.at(1) == QLatin1Char(':')
+           && path.at(2) == QLatin1Char('/'));
 #else // !Q_OS_WINRT
-    return m_filePath == QDir::rootPath();
+    return path == QDir::rootPath();
 #endif // !Q_OS_WINRT
 }
-#endif
+#endif // Q_OS_WIN
 
-bool QFileSystemEntry::isRoot() const
+bool QFileSystemEntry::isRootPath(const QString &path)
 {
-    resolveFilePath();
-    if (m_filePath == QLatin1String("/")
+    if (path == QLatin1String("/")
 #if defined(Q_OS_WIN)
-            || isDriveRoot()
-            || isUncRoot(m_filePath)
+            || isDriveRootPath(path)
+            || isUncRoot(path)
 #endif
             )
         return true;
@@ -321,6 +325,12 @@ bool QFileSystemEntry::isRoot() const
     return false;
 }
 
+bool QFileSystemEntry::isRoot() const
+{
+    resolveFilePath();
+    return isRootPath(m_filePath);
+}
+
 bool QFileSystemEntry::isEmpty() const
 {
     return m_filePath.isEmpty() && m_nativeFilePath.isEmpty();

src/corelib/io/qfilesystementry_p.h

@@ -94,6 +94,7 @@ public:
 
 #if defined(Q_OS_WIN)
     bool isDriveRoot() const;
+    static bool isDriveRootPath(const QString &path);
 #endif
     bool isRoot() const;
 
@@ -103,6 +104,8 @@ public:
         *this = QFileSystemEntry();
     }
 
+    Q_CORE_EXPORT static bool isRootPath(const QString &path);
+
 private:
     // creates the QString version out of the bytearray version
     void resolveFilePath() const;

src/widgets/itemviews/qdirmodel.cpp

@@ -52,6 +52,7 @@
 #include <qstyle.h>
 #include <qapplication.h>
 #include <private/qabstractitemmodel_p.h>
+#include <private/qfilesystementry_p.h>
 #include <qdebug.h>
 
 #include <stack>
@@ -1104,8 +1105,9 @@ QString QDirModel::fileName(const QModelIndex &index) const
     if (!d->indexValid(index))
         return QString();
     QFileInfo info = fileInfo(index);
-    if (info.isRoot())
-        return info.absoluteFilePath();
+    const QString &path = info.absoluteFilePath();
+    if (QFileSystemEntry::isRootPath(path))
+        return path;
     if (d->resolveSymlinks && info.isSymLink())
         info = d->resolvedInfo(info);
     return info.fileName();
@@ -1280,8 +1282,8 @@ QString QDirModelPrivate::name(const QModelIndex &index) const
 {
     const QDirNode *n = node(index);
     const QFileInfo info = n->info;
-    if (info.isRoot()) {
-        QString name = info.absoluteFilePath();
+    QString name = info.absoluteFilePath();
+    if (QFileSystemEntry::isRootPath(name)) {
 #if defined(Q_OS_WIN)
         if (name.startsWith(QLatin1Char('/'))) // UNC host
             return info.fileName();

src/widgets/itemviews/qfileiconprovider.cpp

@@ -46,6 +46,7 @@
 #include <private/qfunctions_p.h>
 #include <private/qguiapplication_p.h>
 #include <private/qicon_p.h>
+#include <private/qfilesystementry_p.h>
 #include <qpa/qplatformintegration.h>
 #include <qpa/qplatformservices.h>
 #include <qpa/qplatformtheme.h>
@@ -247,10 +248,11 @@ QIcon QFileIconProvider::icon(const QFileInfo &info) const
     if (!retIcon.isNull())
         return retIcon;
 
-    if (info.isRoot())
+    const QString &path = info.absoluteFilePath();
+    if (path.isEmpty() || QFileSystemEntry::isRootPath(path))
 #if defined (Q_OS_WIN) && !defined(Q_OS_WINRT)
     {
-        UINT type = GetDriveType((wchar_t *)info.absoluteFilePath().utf16());
+        UINT type = GetDriveType(reinterpret_cast<const wchar_t *>(path.utf16()));
 
         switch (type) {
         case DRIVE_REMOVABLE:
@@ -298,7 +300,7 @@ QIcon QFileIconProvider::icon(const QFileInfo &info) const
 
 QString QFileIconProvider::type(const QFileInfo &info) const
 {
-    if (info.isRoot())
+    if (QFileSystemEntry::isRootPath(info.absoluteFilePath()))
         return QApplication::translate("QFileDialog", "Drive");
     if (info.isFile()) {
         if (!info.suffix().isEmpty()) {