QTemporaryFile: add a simpler rename() (non-virtual) override

Calling the parent version is still ok, but if you call the new one you
get a bit of benefit. Since we control the file name, we don't have to
worry about a case-changing renaming (by choice). We also know that the
file is a regular one, because we created it.

[ChangeLog][Important Behavior Changes][QTemporaryFile] rename() no
longer attempts to do block copying, as that usually indicates a mistake
in the user's code. Instead, either create the temporary file in the
same directory as the new name to be, or use QSaveFile.

Change-Id: I1eba2b016de74620bfc8fffd14ccaac0cdb9fe87
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

src/corelib/io/qtemporaryfile.cpp

@@ -54,6 +54,8 @@
 
 #if defined(QT_BUILD_CORE_LIB)
 #include "qcoreapplication.h"
+#else
+#define tr(X) QString::fromLatin1(X)
 #endif
 
 QT_BEGIN_NAMESPACE
@@ -686,6 +688,36 @@ void QTemporaryFile::setFileTemplate(const QString &name)
         static_cast<QTemporaryFileEngine*>(d->fileEngine)->setFileTemplate(name);
 }
 
+/*!
+    \internal
+
+    This is just a simplified version of QFile::rename() because we know a few
+    extra details about what kind of file we have. The documentation is hidden
+    from the user because QFile::rename() should be enough.
+*/
+bool QTemporaryFile::rename(const QString &newName)
+{
+    Q_D(QTemporaryFile);
+    auto tef = static_cast<QTemporaryFileEngine *>(d->fileEngine);
+    if (!tef || !tef->isReallyOpen() || !tef->filePathWasTemplate)
+        return QFile::rename(newName);
+
+    unsetError();
+    close();
+    if (error() == QFile::NoError) {
+        if (tef->rename(newName)) {
+            unsetError();
+            // engine was able to handle the new name so we just reset it
+            tef->setFileName(newName);
+            d->fileName = newName;
+            return true;
+        }
+
+        d->setError(QFile::RenameError, tef->errorString());
+    }
+    return false;
+}
+
 /*!
   \fn QTemporaryFile *QTemporaryFile::createLocalFile(const QString &fileName)
   \overload

src/corelib/io/qtemporaryfile.h

@@ -80,6 +80,10 @@ public:
     QString fileName() const Q_DECL_OVERRIDE;
     QString fileTemplate() const;
     void setFileTemplate(const QString &name);
+
+    // Hides QFile::rename
+    bool rename(const QString &newName);
+
 #if QT_DEPRECATED_SINCE(5,1)
     QT_DEPRECATED inline static QTemporaryFile *createLocalFile(const QString &fileName)
         { return createNativeFile(fileName); }