QXcbWindow: use an accessor to get the screen instead of storing it

Applications which construct a window with one screen configuration and show
the window later on after a screen configuration change crash because the
QXcbWindow::m_screen still pointed to the screen present at the time of window
construction. In QXcbWindow::handleConfigureNotifyEvent the m_screen should get
updated with the new screen, but I didn't see that method called in the
scenario outlined. Looking at the other platform backends, I however see that
they take the screen directly from the QPlatformWindow instead of storing the
instance, hence this patch which makes QXcbWindow do the same.

Change-Id: I13759a5939315c3aac36ec6e2c25bd0a6d7b1c35
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qxcbglxwindow.cpp b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qxcbglxwindow.cpp
index 8aabde8129..8d5bfb13d3 100644
--- a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qxcbglxwindow.cpp
+++ b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qxcbglxwindow.cpp
@@ -62,7 +62,10 @@ void QXcbGlxWindow::resolveFormat()
 
 void *QXcbGlxWindow::createVisual()
 {
-    return qglx_findVisualInfo(DISPLAY_FROM_XCB(m_screen), m_screen->screenNumber(), &m_format);
+    QXcbScreen *scr = xcbScreen();
+    if (!scr)
+        return Q_NULLPTR;
+    return qglx_findVisualInfo(DISPLAY_FROM_XCB(scr), scr->screenNumber(), &m_format);
 }
 
 QT_END_NAMESPACE