Offscreen QPA: implement a native interface

Many code paths simply expect to have a native interface
available, and won't check if a plugin is returning nullptr
for it. This leads to crashes or local workarounds
(e.g. 3197932e6fb03fb9c0ff669af858cb94e3836d79). Instead,
have offscreen implement a dummy native interface.

This requires shuffling some code for the X11 integration.

Pick-to: 5.15
Change-Id: I2bdceee379e4ded9b085ebbb4d03d1e074f60726
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/plugins/platforms/offscreen/qoffscreenintegration.h b/src/plugins/platforms/offscreen/qoffscreenintegration.h
index be47313913..38d145eee3 100644
--- a/src/plugins/platforms/offscreen/qoffscreenintegration.h
+++ b/src/plugins/platforms/offscreen/qoffscreenintegration.h
@@ -71,19 +71,22 @@ public:
     QPlatformFontDatabase *fontDatabase() const override;
     QAbstractEventDispatcher *createEventDispatcher() const override;
 
+    QPlatformNativeInterface *nativeInterface() const override;
+
     QStringList themeNames() const override;
     QPlatformTheme *createPlatformTheme(const QString &name) const override;
 
     static QOffscreenIntegration *createOffscreenIntegration(const QStringList& paramList);
 
     QList<QPlatformScreen *> screens() const;
-private:
+protected:
     QScopedPointer<QPlatformFontDatabase> m_fontDatabase;
 #if QT_CONFIG(draganddrop)
     QScopedPointer<QPlatformDrag> m_drag;
 #endif
     QScopedPointer<QPlatformInputContext> m_inputContext;
     QScopedPointer<QPlatformServices> m_services;
+    mutable QScopedPointer<QPlatformNativeInterface> m_nativeInterface;
     QList<QPlatformScreen *> m_screens;
     bool m_windowFrameMarginsEnabled = true;
 };