QEventDispatcherWin32: get rid of the hook procedure

Instead of intercepting the WM_QT_SENDPOSTEDEVENTS message in the hook
procedure, we can handle it at receive points, making
qt_GetMessageHook() unnecessary.

Including general performance improvements, this patch fixes the issue
where some applications (e.g. Ableton Live) do not call a chain of
nested hooks for plugins.

Pick-to: 6.1 5.15
Fixes: QTBUG-90949
Change-Id: If8e96848392c6f10d45af2aac0567707d16af673
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Nuno Santos <nunosantos@imaginando.net>

2 files changed, 9 insertions, 30 deletions

diff --git a/src/corelib/kernel/qeventdispatcher_win.cpp b/src/corelib/kernel/qeventdispatcher_win.cpp
index 3609bfe389..19604de32f 100644
--- a/src/corelib/kernel/qeventdispatcher_win.cpp
+++ b/src/corelib/kernel/qeventdispatcher_win.cpp
@@ -96,7 +96,7 @@ LRESULT QT_WIN_CALLBACK qt_internal_proc(HWND hwnd, UINT message, WPARAM wp, LPA
 
 QEventDispatcherWin32Private::QEventDispatcherWin32Private()
     : interrupt(false), internalHwnd(0),
-      getMessageHook(0), sendPostedEventsTimerId(0), wakeUps(0),
+      sendPostedEventsTimerId(0), wakeUps(0),
       activateNotifiersPosted(false)
 {
 }
@@ -251,30 +251,21 @@ LRESULT QT_WIN_CALLBACK qt_internal_proc(HWND hwnd, UINT message, WPARAM wp, LPA
         static const UINT mask = inputQueueMask();
         if (HIWORD(GetQueueStatus(mask)) == 0)
             q->sendPostedEvents();
+        else
+            d->startPostedEventsTimer();
         return 0;
     } // switch (message)
 
     return DefWindowProc(hwnd, message, wp, lp);
 }
 
-LRESULT QT_WIN_CALLBACK qt_GetMessageHook(int code, WPARAM wp, LPARAM lp)
+void QEventDispatcherWin32Private::startPostedEventsTimer()
 {
-    QEventDispatcherWin32 *q = qobject_cast<QEventDispatcherWin32 *>(QAbstractEventDispatcher::instance());
-    Q_ASSERT(q != nullptr);
-    QEventDispatcherWin32Private *d = q->d_func();
-    MSG *msg = reinterpret_cast<MSG *>(lp);
-    // Windows unexpectedly passes PM_NOYIELD flag to the hook procedure,
-    // if ::PeekMessage(..., PM_REMOVE | PM_NOYIELD) is called from the event loop.
-    // So, retrieve 'removed' tag as a bit field.
-    const bool messageRemoved = (wp & PM_REMOVE) != 0;
-
-    if (msg->hwnd == d->internalHwnd && msg->message == WM_QT_SENDPOSTEDEVENTS
-        && messageRemoved && d->sendPostedEventsTimerId == 0) {
+    if (sendPostedEventsTimerId == 0) {
         // Start a timer to deliver posted events when the message queue is emptied.
-        d->sendPostedEventsTimerId = SetTimer(d->internalHwnd, SendPostedEventsTimerId,
-                                              USER_TIMER_MINIMUM, NULL);
+        sendPostedEventsTimerId = SetTimer(internalHwnd, SendPostedEventsTimerId,
+                                           USER_TIMER_MINIMUM, NULL);
     }
-    return d->getMessageHook ? CallNextHookEx(0, code, wp, lp) : 0;
 }
 
 // Provide class name and atom for the message window used by
@@ -458,14 +449,6 @@ QEventDispatcherWin32::QEventDispatcherWin32(QEventDispatcherWin32Private &dd, Q
     Q_D(QEventDispatcherWin32);
 
     d->internalHwnd = qt_create_internal_window(this);
-
-    // setup GetMessage hook needed to drive our posted events
-    d->getMessageHook = SetWindowsHookEx(WH_GETMESSAGE, (HOOKPROC) qt_GetMessageHook, NULL, GetCurrentThreadId());
-    if (Q_UNLIKELY(!d->getMessageHook)) {
-        int errorCode = GetLastError();
-        qFatal("Qt: INTERNAL ERROR: failed to install GetMessage hook: %d, %ls",
-               errorCode, qUtf16Printable(qt_error_string(errorCode)));
-    }
 }
 
 QEventDispatcherWin32::~QEventDispatcherWin32()
@@ -536,6 +519,7 @@ bool QEventDispatcherWin32::processEvents(QEventLoop::ProcessEventsFlags flags)
             }
 
             if (d->internalHwnd == msg.hwnd && msg.message == WM_QT_SENDPOSTEDEVENTS) {
+                d->startPostedEventsTimer();
                 // Set result to 'true' because the message was sent by wakeUp().
                 retVal = true;
                 continue;
@@ -865,10 +849,6 @@ void QEventDispatcherWin32::closingDown()
 
     d->closingDown = true;
 
-    if (d->getMessageHook)
-        UnhookWindowsHookEx(d->getMessageHook);
-    d->getMessageHook = 0;
-
     if (d->sendPostedEventsTimerId != 0)
         KillTimer(d->internalHwnd, d->sendPostedEventsTimerId);
     d->sendPostedEventsTimerId = 0;
diff --git a/src/corelib/kernel/qeventdispatcher_win_p.h b/src/corelib/kernel/qeventdispatcher_win_p.h
index 90a818b0f5..49a6d3ebbc 100644
--- a/src/corelib/kernel/qeventdispatcher_win_p.h
+++ b/src/corelib/kernel/qeventdispatcher_win_p.h
@@ -104,7 +104,6 @@ protected:
 
 private:
     friend LRESULT QT_WIN_CALLBACK qt_internal_proc(HWND hwnd, UINT message, WPARAM wp, LPARAM lp);
-    friend LRESULT QT_WIN_CALLBACK qt_GetMessageHook(int, WPARAM, LPARAM);
 };
 
 struct QSockNot {
@@ -154,11 +153,11 @@ public:
 
     // internal window handle used for socketnotifiers/timers/etc
     HWND internalHwnd;
-    HHOOK getMessageHook;
 
     // for controlling when to send posted events
     UINT_PTR sendPostedEventsTimerId;
     QAtomicInt wakeUps;
+    void startPostedEventsTimer();
 
     // timers
     WinTimerDict timerDict;