From 9981538a1d1088bab623c16d42819790d112e095 Mon Sep 17 00:00:00 2001
From: Fatih Uzunoglu <fuzun54@outlook.com>
Date: Wed, 19 Feb 2025 18:32:46 +0200
Subject: [PATCH] contrib: qtbase: add patch to treat queued connections fairly
on windows
On Windows, Qt does not treat queued connections fairly. This is a problem
for us, because most of the operations we are doing are asynchronous, for
optimization or utility reasons.
For example, the texture sub-rect geometry is a delayed binding as we don't
want to apply effect for texture if the result is just going to be dismissed
(due to geometry change, effect needs to be applied again).
We also use delayed bindings in complex layouting, such as within the player
control bar where controls need to be invisible when they no longer fit into
the space (unless expandable).
In summary, this seems to how Qt behave with regard to queued connections:
- In the worst case (messages are constantly pushed), they may be delayed
forever if Windows keep sending messages. This is the case with window
resize, for example.
- In the average case (there were messages when event dispatcher
encountered with a queued call), they are delayed by 10~ milliseconds.
- In the best case, there is no delay, but this is rare for a GUI
application, as GUI applications almost always have messages due to
user interaction.
---
...cherWin32-treat-posted-events-fairly.patch | 148 ++++++++++++++++++
contrib/src/qt/rules.mak | 1 +
2 files changed, 149 insertions(+)
create mode 100644 contrib/src/qt/0001-QEventDispatcherWin32-treat-posted-events-fairly.patch
diff --git a/contrib/src/qt/0001-QEventDispatcherWin32-treat-posted-events-fairly.patch b/contrib/src/qt/0001-QEventDispatcherWin32-treat-posted-events-fairly.patch
new file mode 100644
index 000000000000..a18f6648842f
--- /dev/null
+++ b/contrib/src/qt/0001-QEventDispatcherWin32-treat-posted-events-fairly.patch
@@ -0,0 +1,148 @@
+From c60305a7564c63c9e175ba65e721df1db6855251 Mon Sep 17 00:00:00 2001
+From: Fatih Uzunoglu <fuzun54@outlook.com>
+Date: Tue, 18 Feb 2025 23:29:57 +0200
+Subject: [PATCH] QEventDispatcherWin32: treat posted events fairly
+
+By processing at least a batch of posted events
+while prioritizing other message types.
+---
+ src/corelib/kernel/qcoreapplication.cpp | 10 ++++++++--
+ src/corelib/kernel/qcoreapplication_p.h | 2 +-
+ src/corelib/kernel/qeventdispatcher_win.cpp | 13 +++++++++++--
+ src/corelib/kernel/qeventdispatcher_win_p.h | 2 +-
+ .../platform/windows/qwindowsguieventdispatcher.cpp | 4 ++--
+ .../platform/windows/qwindowsguieventdispatcher_p.h | 2 +-
+ 6 files changed, 24 insertions(+), 9 deletions(-)
+
+diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
+index 48c75973f7f..83ed71c23e9 100644
+--- a/src/corelib/kernel/qcoreapplication.cpp
++++ b/src/corelib/kernel/qcoreapplication.cpp
+@@ -1801,7 +1801,7 @@ void QCoreApplication::sendPostedEvents(QObject *receiver, int event_type)
+ }
+
+ void QCoreApplicationPrivate::sendPostedEvents(QObject *receiver, int event_type,
+- QThreadData *data)
++ QThreadData *data, qsizetype count)
+ {
+ if (event_type == -1) {
+ // we were called by an obsolete event dispatcher.
+@@ -1873,7 +1873,13 @@ void QCoreApplicationPrivate::sendPostedEvents(QObject *receiver, int event_type
+ };
+ CleanUp cleanup(receiver, event_type, data);
+
+- while (i < data->postEventList.size()) {
++ qsizetype amount;
++ if (count <= 0) // if 0, process all events, which is the default behavior
++ amount = data->postEventList.size();
++ else
++ amount = std::min<qsizetype>(i + count, data->postEventList.size());
++
++ while (i < amount) {
+ // avoid live-lock
+ if (i >= data->postEventList.insertionOffset)
+ break;
+diff --git a/src/corelib/kernel/qcoreapplication_p.h b/src/corelib/kernel/qcoreapplication_p.h
+index 0a51a0b5de8..dd85bb59d2c 100644
+--- a/src/corelib/kernel/qcoreapplication_p.h
++++ b/src/corelib/kernel/qcoreapplication_p.h
+@@ -107,7 +107,7 @@ public:
+ static QThread *mainThread();
+ static bool threadRequiresCoreApplication();
+
+- static void sendPostedEvents(QObject *receiver, int event_type, QThreadData *data);
++ static void sendPostedEvents(QObject *receiver, int event_type, QThreadData *data, qsizetype count = 0);
+
+ static void checkReceiverThread(QObject *receiver);
+ void cleanupThreadData();
+diff --git a/src/corelib/kernel/qeventdispatcher_win.cpp b/src/corelib/kernel/qeventdispatcher_win.cpp
+index 78ad3d3edeb..7c247724d09 100644
+--- a/src/corelib/kernel/qeventdispatcher_win.cpp
++++ b/src/corelib/kernel/qeventdispatcher_win.cpp
+@@ -37,6 +37,8 @@ QT_BEGIN_NAMESPACE
+ #endif
+ #endif // QT_NO_GESTURES
+
++#define POSTEDEVENTS_BATCH 32
++
+ enum {
+ WM_QT_SOCKETNOTIFIER = WM_USER,
+ WM_QT_SENDPOSTEDEVENTS = WM_USER + 1,
+@@ -204,7 +206,14 @@ LRESULT QT_WIN_CALLBACK qt_internal_proc(HWND hwnd, UINT message, WPARAM wp, LPA
+ if (HIWORD(GetQueueStatus(mask)) == 0)
+ q->sendPostedEvents();
+ else
++ {
++ // Fair treatment for posted events,
++ // at least process some of the pending events:
++ q->sendPostedEvents(POSTEDEVENTS_BATCH);
++ // We still need this, because there can be more than
++ // POSTEDEVENTS_BATCH posted events waiting to be processed:
+ d->startPostedEventsTimer();
++ }
+ return 0;
+ } // switch (message)
+
+@@ -893,7 +902,7 @@ bool QEventDispatcherWin32::event(QEvent *e)
+ return QAbstractEventDispatcher::event(e);
+ }
+
+-void QEventDispatcherWin32::sendPostedEvents()
++void QEventDispatcherWin32::sendPostedEvents(qsizetype count)
+ {
+ Q_D(QEventDispatcherWin32);
+
+@@ -904,7 +913,7 @@ void QEventDispatcherWin32::sendPostedEvents()
+ // Allow posting WM_QT_SENDPOSTEDEVENTS message.
+ d->wakeUps.storeRelaxed(0);
+
+- QCoreApplicationPrivate::sendPostedEvents(0, 0, d->threadData.loadRelaxed());
++ QCoreApplicationPrivate::sendPostedEvents(0, 0, d->threadData.loadRelaxed(), count);
+ }
+
+ HWND QEventDispatcherWin32::internalHwnd()
+diff --git a/src/corelib/kernel/qeventdispatcher_win_p.h b/src/corelib/kernel/qeventdispatcher_win_p.h
+index 558490a85e8..d805655b833 100644
+--- a/src/corelib/kernel/qeventdispatcher_win_p.h
++++ b/src/corelib/kernel/qeventdispatcher_win_p.h
+@@ -62,7 +62,7 @@ public:
+
+ protected:
+ QEventDispatcherWin32(QEventDispatcherWin32Private &dd, QObject *parent = nullptr);
+- virtual void sendPostedEvents();
++ virtual void sendPostedEvents(qsizetype count = 0);
+ void doUnregisterSocketNotifier(QSocketNotifier *notifier);
+
+ private:
+diff --git a/src/gui/platform/windows/qwindowsguieventdispatcher.cpp b/src/gui/platform/windows/qwindowsguieventdispatcher.cpp
+index c2f0efe96ef..d3a818634fd 100644
+--- a/src/gui/platform/windows/qwindowsguieventdispatcher.cpp
++++ b/src/gui/platform/windows/qwindowsguieventdispatcher.cpp
+@@ -38,9 +38,9 @@ bool QWindowsGuiEventDispatcher::processEvents(QEventLoop::ProcessEventsFlags fl
+ return rc;
+ }
+
+-void QWindowsGuiEventDispatcher::sendPostedEvents()
++void QWindowsGuiEventDispatcher::sendPostedEvents(qsizetype count)
+ {
+- QEventDispatcherWin32::sendPostedEvents();
++ QEventDispatcherWin32::sendPostedEvents(count);
+ QWindowSystemInterface::sendWindowSystemEvents(m_flags);
+ }
+
+diff --git a/src/gui/platform/windows/qwindowsguieventdispatcher_p.h b/src/gui/platform/windows/qwindowsguieventdispatcher_p.h
+index 7d326c07808..d7ee009f1a0 100644
+--- a/src/gui/platform/windows/qwindowsguieventdispatcher_p.h
++++ b/src/gui/platform/windows/qwindowsguieventdispatcher_p.h
+@@ -29,7 +29,7 @@ public:
+ static const char *windowsMessageName(UINT msg);
+
+ bool QT_ENSURE_STACK_ALIGNED_FOR_SSE processEvents(QEventLoop::ProcessEventsFlags flags) override;
+- void sendPostedEvents() override;
++ void sendPostedEvents(qsizetype count = 0) override;
+
+ private:
+ QEventLoop::ProcessEventsFlags m_flags;
+--
+2.48.1
+
diff --git a/contrib/src/qt/rules.mak b/contrib/src/qt/rules.mak
index 3c44998e035f..891359d440f1 100644
--- a/contrib/src/qt/rules.mak
+++ b/contrib/src/qt/rules.mak
@@ -54,6 +54,7 @@ qt: qtbase-everywhere-src-$(QTBASE_VERSION_FULL).tar.xz .sum-qt
$(APPLY) $(SRC)/qt/0001-disable-precompiled-headers-when-forcing-WINVER-inte.patch
$(APPLY) $(SRC)/qt/0001-Use-DirectWrite-font-database-only-with-Windows-10-a.patch
$(APPLY) $(SRC)/qt/0003-Do-not-link-D3D9.patch
+ $(APPLY) $(SRC)/qt/0001-QEventDispatcherWin32-treat-posted-events-fairly.patch
$(MOVE)
ifdef HAVE_WIN32
--
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