Don't replay mouse press event which closes a popup on X11

Add a new style hint to QPlatformIntegration: ReplayMousePressOutsidePopup.
Return false for it in the xcb plugin.

This commit restores the behavior which was in Qt 4.

Task-number: QTBUG-34814
Change-Id: I19fee762395a51475cc67b52b368c70679ca736b
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

src/gui/kernel/qplatformintegration.cpp

@@ -392,6 +392,8 @@ QVariant QPlatformIntegration::styleHint(StyleHint hint) const
         return QPlatformTheme::defaultThemeHint(QPlatformTheme::MousePressAndHoldInterval);
     case TabFocusBehavior:
         return QPlatformTheme::defaultThemeHint(QPlatformTheme::TabFocusBehavior);
+    case ReplayMousePressOutsidePopup:
+        return true;
     }
 
     return 0;

src/gui/kernel/qplatformintegration.h

@@ -145,7 +145,8 @@ public:
         SetFocusOnTouchRelease,
         ShowIsMaximized,
         MousePressAndHoldInterval,
-        TabFocusBehavior
+        TabFocusBehavior,
+        ReplayMousePressOutsidePopup
     };
 
     virtual QVariant styleHint(StyleHint hint) const;

src/plugins/platforms/xcb/qxcbintegration.cpp

@@ -374,6 +374,8 @@ QVariant QXcbIntegration::styleHint(QPlatformIntegration::StyleHint hint) const
         // X11 always has support for windows, but the
         // window manager could prevent it (e.g. matchbox)
         return false;
+    case QPlatformIntegration::ReplayMousePressOutsidePopup:
+        return false;
     default:
         break;
     }

src/widgets/kernel/qwidgetwindow.cpp

@@ -465,7 +465,8 @@ void QWidgetWindow::handleMouseEvent(QMouseEvent *event)
         }
 
         if (qApp->activePopupWidget() != activePopupWidget
-            && qt_replay_popup_mouse_event) {
+            && qt_replay_popup_mouse_event
+            && QGuiApplicationPrivate::platformIntegration()->styleHint(QPlatformIntegration::ReplayMousePressOutsidePopup).toBool()) {
             if (m_widget->windowType() != Qt::Popup)
                 qt_button_down = 0;
             if (event->type() == QEvent::MouseButtonPress) {