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>

1 files changed, 13 insertions, 0 deletions

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);