macOS: Clear event dispatcher interrupt state

A pending interrupt of a QEventLoop may interfere with
native runModal calls, resulting in Cocoa's main event
loop to be stopped unexpectedly.

After commit 9ab60b9c processEvents() no longer resets
the event dispatcher interrupt flag.

Add QCocoaEventDispatcher::clearCurrentThreadCocoa
EventDispatcherInterruptFlag(). Use it to clear the
interrupt state before calling runModal and variants.

Work around the inability to use platform API in
the print support code.

Change-Id: I52f26f99a63cbb46969db42f65b09a3c3119ad15
Task-number: QTBUG-56746
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@qt.io>

7 files changed, 38 insertions, 0 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoacolordialoghelper.mm b/src/plugins/platforms/cocoa/qcocoacolordialoghelper.mm
index 3c924bec94..474e2cdb19 100644
--- a/src/plugins/platforms/cocoa/qcocoacolordialoghelper.mm
+++ b/src/plugins/platforms/cocoa/qcocoacolordialoghelper.mm
@@ -39,6 +39,7 @@
 #include <QtCore/qtimer.h>
 
 #include "qcocoahelpers.h"
+#include "qcocoaeventdispatcher.h"
 
 #import <AppKit/AppKit.h>
 
@@ -318,6 +319,10 @@ QT_NAMESPACE_ALIAS_OBJC_CLASS(QNSColorPanelDelegate);
     // cleanup of modal sessions. Do this before showing the native dialog, otherwise it will
     // close down during the cleanup.
     qApp->processEvents(QEventLoop::ExcludeUserInputEvents | QEventLoop::ExcludeSocketNotifiers);
+
+    // Make sure we don't interrupt the runModalForWindow call.
+    QCocoaEventDispatcher::clearCurrentThreadCocoaEventDispatcherInterruptFlag();
+
     [NSApp runModalForWindow:mColorPanel];
     mDialogIsExecuting = false;
     return (mResultCode == NSOKButton);
diff --git a/src/plugins/platforms/cocoa/qcocoaeventdispatcher.h b/src/plugins/platforms/cocoa/qcocoaeventdispatcher.h
index 8a2a478a72..569dd3b028 100644
--- a/src/plugins/platforms/cocoa/qcocoaeventdispatcher.h
+++ b/src/plugins/platforms/cocoa/qcocoaeventdispatcher.h
@@ -125,6 +125,8 @@ public:
     void interrupt();
     void flush();
 
+    static void clearCurrentThreadCocoaEventDispatcherInterruptFlag();
+
     friend void qt_mac_maybeCancelWaitForMoreEventsForwarder(QAbstractEventDispatcher *eventDispatcher);
 };
 
diff --git a/src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm b/src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm
index 1cfb3ecff9..09a0e14950 100644
--- a/src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm
+++ b/src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm
@@ -960,6 +960,19 @@ void QCocoaEventDispatcher::interrupt()
 void QCocoaEventDispatcher::flush()
 { }
 
+// QTBUG-56746: The behavior of processEvents() has been changed to not clear
+// the interrupt flag. Use this function to clear it.
+ void QCocoaEventDispatcher::clearCurrentThreadCocoaEventDispatcherInterruptFlag()
+{
+    QCocoaEventDispatcher *cocoaEventDispatcher =
+            qobject_cast<QCocoaEventDispatcher *>(QThread::currentThread()->eventDispatcher());
+    if (!cocoaEventDispatcher)
+        return;
+    QCocoaEventDispatcherPrivate *cocoaEventDispatcherPrivate =
+            static_cast<QCocoaEventDispatcherPrivate *>(QObjectPrivate::get(cocoaEventDispatcher));
+    cocoaEventDispatcherPrivate->interrupt = false;
+}
+
 QCocoaEventDispatcher::~QCocoaEventDispatcher()
 {
     Q_D(QCocoaEventDispatcher);
diff --git a/src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm b/src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm
index 4c1b190b9c..71748ae77f 100644
--- a/src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm
+++ b/src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm
@@ -45,6 +45,7 @@
 #include "qt_mac_p.h"
 #include "qcocoahelpers.h"
 #include "qcocoamenubar.h"
+#include "qcocoaeventdispatcher.h"
 #include <qregexp.h>
 #include <qbuffer.h>
 #include <qdebug.h>
@@ -235,6 +236,10 @@ static QString strippedText(QString s)
     // cleanup of modal sessions. Do this before showing the native dialog, otherwise it will
     // close down during the cleanup.
     qApp->processEvents(QEventLoop::ExcludeUserInputEvents | QEventLoop::ExcludeSocketNotifiers);
+
+    // Make sure we don't interrupt the runModal call below.
+    QCocoaEventDispatcher::clearCurrentThreadCocoaEventDispatcherInterruptFlag();
+
     QCocoaMenuBar::redirectKnownMenuItemsToFirstResponder();
     mReturnCode = [mSavePanel runModal];
     QCocoaMenuBar::resetKnownMenuItemsToQt();
diff --git a/src/plugins/platforms/cocoa/qcocoafontdialoghelper.mm b/src/plugins/platforms/cocoa/qcocoafontdialoghelper.mm
index 5b27dc1da9..eb800afd47 100644
--- a/src/plugins/platforms/cocoa/qcocoafontdialoghelper.mm
+++ b/src/plugins/platforms/cocoa/qcocoafontdialoghelper.mm
@@ -43,6 +43,7 @@
 #include <private/qfontengine_coretext_p.h>
 
 #include "qcocoahelpers.h"
+#include "qcocoaeventdispatcher.h"
 
 #import <AppKit/AppKit.h>
 
@@ -313,6 +314,10 @@ QT_NAMESPACE_ALIAS_OBJC_CLASS(QNSFontPanelDelegate);
     // cleanup of modal sessions. Do this before showing the native dialog, otherwise it will
     // close down during the cleanup.
     qApp->processEvents(QEventLoop::ExcludeUserInputEvents | QEventLoop::ExcludeSocketNotifiers);
+
+    // Make sure we don't interrupt the runModalForWindow call.
+    QCocoaEventDispatcher::clearCurrentThreadCocoaEventDispatcherInterruptFlag();
+
     [NSApp runModalForWindow:mFontPanel];
     mDialogIsExecuting = false;
     return (mResultCode == NSOKButton);
diff --git a/src/plugins/platforms/cocoa/qcocoanativeinterface.h b/src/plugins/platforms/cocoa/qcocoanativeinterface.h
index d018c05635..d6786b9274 100644
--- a/src/plugins/platforms/cocoa/qcocoanativeinterface.h
+++ b/src/plugins/platforms/cocoa/qcocoanativeinterface.h
@@ -96,6 +96,8 @@ private:
     */
     Q_INVOKABLE QPixmap defaultBackgroundPixmapForQWizard();
 
+    Q_INVOKABLE void clearCurrentThreadCocoaEventDispatcherInterruptFlag();
+
     // QMacPastebardMime support. The mac pasteboard void pointers are
     // QMacPastebardMime instances from the cocoa plugin or qtmacextras
     // These two classes are kept in sync and can be casted between.
diff --git a/src/plugins/platforms/cocoa/qcocoanativeinterface.mm b/src/plugins/platforms/cocoa/qcocoanativeinterface.mm
index baee451903..8534c1c6fb 100644
--- a/src/plugins/platforms/cocoa/qcocoanativeinterface.mm
+++ b/src/plugins/platforms/cocoa/qcocoanativeinterface.mm
@@ -38,6 +38,7 @@
 #include "qcocoahelpers.h"
 #include "qcocoaapplication.h"
 #include "qcocoaintegration.h"
+#include "qcocoaeventdispatcher.h"
 
 #include <qbytearray.h>
 #include <qwindow.h>
@@ -193,6 +194,11 @@ QPixmap QCocoaNativeInterface::defaultBackgroundPixmapForQWizard()
     return QPixmap();
 }
 
+void QCocoaNativeInterface::clearCurrentThreadCocoaEventDispatcherInterruptFlag()
+{
+    QCocoaEventDispatcher::clearCurrentThreadCocoaEventDispatcherInterruptFlag();
+}
+
 void QCocoaNativeInterface::onAppFocusWindowChanged(QWindow *window)
 {
     Q_UNUSED(window);