Make sure timestamp is initialized before using it for seting selection owner.

Convention from icccm: Clients attempting to acquire a selection must set
the time value of the xcb_set_selection_owner request to the timestamp of
the event triggering the acquisition attempt, not to XCB_CURRENT_TIME. In
some cases it happened that timestamp was set to XCB_CURRENT_TIME.

A zero-length append to a property is a way to obtain a timestamp for this
purpose; the timestamp is in the corresponding XCB_PROPERTY_NOTIFY event.
We used to have this mechanism in 4.8, it was achieved by XWindowEvent.

AFAIK there isn't an equivalent for XWindowEvent in XCB. Therefore i had to
introduce a new mechanism in QXcbConnection - getTimestamp. This function
blocks until it receives the requested event.

Change-Id: Ide46a4fdd44cf026fdd17a79d3c4b17741d1b7d4
Task-number: QTBUG-26783
Reviewed-by: Uli Schlachter <psychon@znc.in>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/plugins/platforms/xcb/qxcbclipboard.cpp b/src/plugins/platforms/xcb/qxcbclipboard.cpp
index f021ab8b4a..142a8dfcde 100644
--- a/src/plugins/platforms/xcb/qxcbclipboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbclipboard.cpp
@@ -300,6 +300,9 @@ void QXcbClipboard::setMimeData(QMimeData *data, QClipboard::Mode mode)
         m_timestamp[mode] = XCB_CURRENT_TIME;
     }
 
+    if (connection()->time() == XCB_CURRENT_TIME)
+        connection()->setTime(connection()->getTimestamp());
+
     if (data) {
         newOwner = owner();