tdf#137639 qt: UTF-16-encode mime data for "text/plain;charset=utf-16"

Return a `QVariant` from a `QByteArray` containing the UTF-16-encoded
characters when mime data for mime type "text/plain;charset=utf-16"
is requested in `QtMimeData::retrieveData`, rather than
a `QVariant` created from a a `QString`, to ensure that UTF-16
encoded data is actually used in the end.

While `QString` uses UTF-16 encoding itself,
`QMimeDataPrivate::retrieveTypedData` from the Qt library
would convert the retrieved `QString` data to UTF-8 [1],
resulting in a mismatch because UTF-8 encoded data would
actually be returned when UTF-16-encoded one has
been requested.

This gets called as follows:

0 QtMimeData::retrieveData
1 QMimeDataPrivate::retrieveTypedData
2 QMimeData::data
3 QtMimeData::deepCopy

[1] https://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/kernel/qmimedata.cpp?h=6.3.0#n212

Change-Id: I3db1476838336682584145fb43d397c8eed29ce2
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/134456
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/vcl/qt5/QtTransferable.cxx b/vcl/qt5/QtTransferable.cxx
index db52eed66d0b..d9e0beaa71d3 100644
--- a/vcl/qt5/QtTransferable.cxx
+++ b/vcl/qt5/QtTransferable.cxx
@@ -338,6 +338,11 @@ QVariant QtMimeData::retrieveData(const QString& mimeType, QMetaType) const
             OString aLocaleString(OUStringToOString(aString, osl_getThreadTextEncoding()));
             aByteArray = QByteArray(aLocaleString.getStr(), aLocaleString.getLength());
         }
+        else if (bWantUTF16)
+        {
+            aByteArray = QByteArray(reinterpret_cast<const char*>(aString.getStr()),
+                                    aString.getLength() * 2);
+        }
         else
             return QVariant(toQString(aString));
     }