3 files changed, 41 insertions, 2 deletions
diff --git a/src/plugins/platforms/ios/qiosscreen.h b/src/plugins/platforms/ios/qiosscreen.h
index 7f10b08492..d63fa29ec3 100644
--- a/src/plugins/platforms/ios/qiosscreen.h
+++ b/src/plugins/platforms/ios/qiosscreen.h
@@ -46,6 +46,10 @@
 
 @class QIOSOrientationListener;
 
+@interface QUIWindow : UIWindow
+@property (nonatomic, readonly) BOOL sendingEvent;
+@end
+
 QT_BEGIN_NAMESPACE
 
 class QIOSScreen : public QObject, public QPlatformScreen
diff --git a/src/plugins/platforms/ios/qiosscreen.mm b/src/plugins/platforms/ios/qiosscreen.mm
index 67970ba59e..0d3826fc4c 100644
--- a/src/plugins/platforms/ios/qiosscreen.mm
+++ b/src/plugins/platforms/ios/qiosscreen.mm
@@ -192,6 +192,26 @@ static QIOSScreen* qtPlatformScreenFor(UIScreen *uiScreen)
 
 // -------------------------------------------------------------------------
 
+@implementation QUIWindow
+
+- (id)initWithFrame:(CGRect)frame
+{
+    if ((self = [super initWithFrame:frame]))
+        self->_sendingEvent = NO;
+
+    return self;
+}
+
+- (void)sendEvent:(UIEvent *)event
+{
+    QScopedValueRollback<BOOL>(self->_sendingEvent, YES);
+    [super sendEvent:event];
+}
+
+@end
+
+// -------------------------------------------------------------------------
+
 QT_BEGIN_NAMESPACE
 
 /*!
@@ -261,7 +281,7 @@ QIOSScreen::QIOSScreen(UIScreen *screen)
 
     if (!m_uiWindow) {
         // Create a window and associated view-controller that we can use
-        m_uiWindow = [[UIWindow alloc] initWithFrame:[m_uiScreen bounds]];
+        m_uiWindow = [[QUIWindow alloc] initWithFrame:[m_uiScreen bounds]];
         m_uiWindow.rootViewController = [[[QIOSViewController alloc] initWithQIOSScreen:this] autorelease];
     }
 
diff --git a/src/plugins/platforms/ios/quiview.mm b/src/plugins/platforms/ios/quiview.mm
index 79f9d6871a..1dbacad6e7 100644
--- a/src/plugins/platforms/ios/quiview.mm
+++ b/src/plugins/platforms/ios/quiview.mm
@@ -43,6 +43,7 @@
 #include "qiosintegration.h"
 #include "qiosviewcontroller.h"
 #include "qiostextresponder.h"
+#include "qiosscreen.h"
 #include "qioswindow.h"
 #ifndef Q_OS_TVOS
 #include "qiosmenu.h"
@@ -359,7 +360,21 @@
 - (void)sendTouchEventWithTimestamp:(ulong)timeStamp
 {
     QIOSIntegration *iosIntegration = QIOSIntegration::instance();
-    QWindowSystemInterface::handleTouchEvent(m_qioswindow->window(), timeStamp, iosIntegration->touchDevice(), m_activeTouches.values());
+    if (!static_cast<QUIWindow *>(self.window).sendingEvent) {
+        // The event is likely delivered as part of delayed touch delivery, via
+        // _UIGestureEnvironmentSortAndSendDelayedTouches, due to one of the two
+        // _UISystemGestureGateGestureRecognizer instances on the top level window
+        // having its delaysTouchesBegan set to YES. During this delivery, it's not
+        // safe to spin up a recursive event loop, as our calling function is not
+        // reentrant, so any gestures used by the recursive code, e.g. a native
+        // alert dialog, will fail to recognize. To be on the safe side, we deliver
+        // the event asynchronously.
+        QWindowSystemInterface::handleTouchEvent<QWindowSystemInterface::AsynchronousDelivery>(
+            m_qioswindow->window(), timeStamp, iosIntegration->touchDevice(), m_activeTouches.values());
+    } else {
+        QWindowSystemInterface::handleTouchEvent<QWindowSystemInterface::SynchronousDelivery>(
+            m_qioswindow->window(), timeStamp, iosIntegration->touchDevice(), m_activeTouches.values());
+    }
 }
 
 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event