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>

2 files changed, 23 insertions, 10 deletions

diff --git a/src/corelib/io/qfilesystementry.cpp b/src/corelib/io/qfilesystementry.cpp
index de4c852068..cbff17d0f1 100644
--- a/src/corelib/io/qfilesystementry.cpp
+++ b/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();
diff --git a/src/corelib/io/qfilesystementry_p.h b/src/corelib/io/qfilesystementry_p.h
index 300a375377..700696d09e 100644
--- a/src/corelib/io/qfilesystementry_p.h
+++ b/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;