Add QPlatformWindow::initialize() for two-step window creation

The QWindow::create method calls createPlatformWindow, and assigns the
result to d->platformWindow. If the platform sends any sort of events
synchronously during the creation, the event will be delivered to a
QWindow that doesn't have a handle() yet, resulting in noop handling
of the event, or crashes.

To mitigate this situations, platforms should do as little a possible
in the QPlatformWindow constructor, and leave initialization to the
new method, where the QWindow will have a handle().

The macOS platform plugin still has a m_initialized guard, to prevent
sending geometry changes during initialization, as this will result
in a resize event before a show event. This forced behavior seems
dubious, but is left for a followup patch.

Task-number: QTBUG-61977
Change-Id: I04d32d93391e89d068752b719270438e7024ad46
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index bd52113762..1d8d6dfc95 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -509,6 +509,8 @@ void QWindowPrivate::create(bool recursive, WId nativeHandle)
         return;
     }
 
+    platformWindow->initialize();
+
     QObjectList childObjects = q->children();
     for (int i = 0; i < childObjects.size(); i ++) {
         QObject *object = childObjects.at(i);