Retrieve drop data with a proper timestamp

Occasionally drag-and-drop was returning empty mimedata due to
using wrong value for timestamp. Accoring to the xdnd specification
we must use timestamp from XdndPosition or XdndDroptime for retrieving
the data.

Task-number: QTBUG-27367
Change-Id: Iadb6b6989cfc4e8ab241e2fd0ded59355108f22f
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

4 files changed, 8 insertions, 4 deletions

diff --git a/src/plugins/platforms/xcb/qxcbclipboard.cpp b/src/plugins/platforms/xcb/qxcbclipboard.cpp
index 3a9eaefa62..f021ab8b4a 100644
--- a/src/plugins/platforms/xcb/qxcbclipboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbclipboard.cpp
@@ -846,13 +846,15 @@ QByteArray QXcbClipboard::getDataInFormat(xcb_atom_t modeAtom, xcb_atom_t fmtAto
     return getSelection(modeAtom, fmtAtom, atom(QXcbAtom::_QT_SELECTION));
 }
 
-QByteArray QXcbClipboard::getSelection(xcb_atom_t selection, xcb_atom_t target, xcb_atom_t property)
+QByteArray QXcbClipboard::getSelection(xcb_atom_t selection, xcb_atom_t target, xcb_atom_t property, xcb_timestamp_t time)
 {
     QByteArray buf;
     xcb_window_t win = requestor();
 
+    if (time == 0) time = connection()->time();
+
     xcb_delete_property(xcb_connection(), win, property);
-    xcb_convert_selection(xcb_connection(), win, selection, target, property, connection()->time());
+    xcb_convert_selection(xcb_connection(), win, selection, target, property, time);
 
     connection()->sync();
 
diff --git a/src/plugins/platforms/xcb/qxcbclipboard.h b/src/plugins/platforms/xcb/qxcbclipboard.h
index 31d99c758d..709ea3b953 100644
--- a/src/plugins/platforms/xcb/qxcbclipboard.h
+++ b/src/plugins/platforms/xcb/qxcbclipboard.h
@@ -84,7 +84,7 @@ public:
     QByteArray getDataInFormat(xcb_atom_t modeAtom, xcb_atom_t fmtatom);
 
     xcb_window_t getSelectionOwner(xcb_atom_t atom) const;
-    QByteArray getSelection(xcb_atom_t selection, xcb_atom_t target, xcb_atom_t property);
+    QByteArray getSelection(xcb_atom_t selection, xcb_atom_t target, xcb_atom_t property, xcb_timestamp_t t = 0);
 
 private:
     xcb_generic_event_t *waitForClipboardEvent(xcb_window_t win, int type, int timeout, bool checkManager = false);
diff --git a/src/plugins/platforms/xcb/qxcbdrag.cpp b/src/plugins/platforms/xcb/qxcbdrag.cpp
index 82a3fc8a83..247b2c991b 100644
--- a/src/plugins/platforms/xcb/qxcbdrag.cpp
+++ b/src/plugins/platforms/xcb/qxcbdrag.cpp
@@ -1233,7 +1233,7 @@ QVariant QXcbDropData::xdndObtainData(const QByteArray &format, QVariant::Type r
         return result; // should never happen?
 
     xcb_atom_t xdnd_selection = c->atom(QXcbAtom::XdndSelection);
-    result = c->clipboard()->getSelection(xdnd_selection, a, xdnd_selection);
+    result = c->clipboard()->getSelection(xdnd_selection, a, xdnd_selection, drag->targetTime());
 
     return mimeConvertToFormat(c, a, result, QLatin1String(format), requestedType, encoding);
 }
diff --git a/src/plugins/platforms/xcb/qxcbdrag.h b/src/plugins/platforms/xcb/qxcbdrag.h
index 19b7dd7f96..ef277e7eec 100644
--- a/src/plugins/platforms/xcb/qxcbdrag.h
+++ b/src/plugins/platforms/xcb/qxcbdrag.h
@@ -98,6 +98,7 @@ public:
     bool dndEnable(QXcbWindow *win, bool on);
 
     void updatePixmap();
+    xcb_timestamp_t targetTime() { return target_time; }
 
 protected:
     void timerEvent(QTimerEvent* e);
@@ -128,6 +129,7 @@ private:
     enum { xdnd_max_type = 100 };
     QList<xcb_atom_t> xdnd_types;
 
+    // timestamp from XdndPosition and XdndDroptime for retrieving the data
     xcb_timestamp_t target_time;
     xcb_timestamp_t source_time;