client: Simplify round trip behavior

The custom event queue was removed in
302d4ffb8549214eb4028dc3e47ec4ee4e12ffbd (2015) so the comment about not
being able to use the inbuilt round trip method no longer applies.

This fixes a real world problem. Use of a blocking round trip should not
process non wayland events. Doing so can lead to misbehaviour client
side as things happen out of order. The move to the event thread created
several regressions as we now get events before the QGuiApplication is
fully constructed.

Change-Id: I650481f49a47ed1a9778c7e1bc3c48db6e8f0031
Reviewed-by: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

1 files changed, 1 insertions, 42 deletions

diff --git a/src/client/qwaylanddisplay.cpp b/src/client/qwaylanddisplay.cpp
index c97e71a9b..489a834d7 100644
--- a/src/client/qwaylanddisplay.cpp
+++ b/src/client/qwaylanddisplay.cpp
@@ -728,50 +728,9 @@ uint32_t QWaylandDisplay::currentTimeMillisec()
     return 0;
 }
 
-static void
-sync_callback(void *data, struct wl_callback *callback, uint32_t serial)
-{
-    Q_UNUSED(serial);
-    bool *done = static_cast<bool *>(data);
-
-    *done = true;
-
-    // If the wl_callback done event is received after the condition check in the while loop in
-    // forceRoundTrip(), but before the call to processEvents, the call to processEvents may block
-    // forever if no more events are posted (eventhough the callback is handled in response to the
-    // aboutToBlock signal). Hence, we wake up the event dispatcher so forceRoundTrip may return.
-    // (QTBUG-64696)
-    if (auto *dispatcher = QThread::currentThread()->eventDispatcher())
-        dispatcher->wakeUp();
-
-    wl_callback_destroy(callback);
-}
-
-static const struct wl_callback_listener sync_listener = {
-    sync_callback
-};
-
 void QWaylandDisplay::forceRoundTrip()
 {
-    // wl_display_roundtrip() works on the main queue only,
-    // but we use a separate one, so basically reimplement it here
-    int ret = 0;
-    bool done = false;
-    wl_callback *callback = wl_display_sync(mDisplay);
-    wl_callback_add_listener(callback, &sync_listener, &done);
-    flushRequests();
-    if (QThread::currentThread()->eventDispatcher()) {
-        while (!done && ret >= 0) {
-            QThread::currentThread()->eventDispatcher()->processEvents(QEventLoop::WaitForMoreEvents);
-            ret = wl_display_dispatch_pending(mDisplay);
-        }
-    } else {
-        while (!done && ret >= 0)
-            ret = wl_display_dispatch(mDisplay);
-    }
-
-    if (ret == -1 && !done)
-        wl_callback_destroy(callback);
+     wl_display_roundtrip(mDisplay);
 }
 
 bool QWaylandDisplay::supportsWindowDecoration() const