From 971dbf2d5be743ddeb998f7461ff3e06ccb892c4 Mon Sep 17 00:00:00 2001
From: David Edmundson <davidedmundson@kde.org>
Date: Wed, 9 Feb 2022 17:20:48 +0000
Subject: [PATCH 38/40] 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>
(cherry picked from commit 62646d9122845d7bd9104b610478cebde3e769c7)
---
 src/client/qwaylanddisplay.cpp | 43 +---------------------------------
 1 file changed, 1 insertion(+), 42 deletions(-)

diff --git a/src/client/qwaylanddisplay.cpp b/src/client/qwaylanddisplay.cpp
index 6f1bada5..86045a35 100644
--- a/src/client/qwaylanddisplay.cpp
+++ b/src/client/qwaylanddisplay.cpp
@@ -611,50 +611,9 @@ 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
-- 
2.35.1