Client: Explicitly send expose window on first configure

Before 46aece51330b6f9b5b4bfd68a5b3b183dc5b1c38 we would always call
QWaylandWindow::applyConfigure which in turn sends an expose event.

Without that clients do not commit their initial buffer.

This adds back the expose event on the first received configure.

Fixes: QTBUG-71509
Change-Id: Ica39bb23245957948e1e1f75caf4f16f7b086ef7
Reviewed-by: Johan Helsing <johan.helsing@qt.io>

src/plugins/platforms/wayland/plugins/shellintegration/xdg-shell-v6/qwaylandxdgshellv6.cpp

@@ -342,6 +342,7 @@ void QWaylandXdgSurfaceV6::zxdg_surface_v6_configure(uint32_t serial)
     if (!m_configured) {
         // We have to do the initial applyConfigure() immediately, since that is the expose.
         applyConfigure();
+        m_exposeRegion = QRegion(QRect(QPoint(), m_window->geometry().size()));
     } else {
         // Later configures are probably resizes, so we have to queue them up for a time when we
         // are not painting to the window.

src/plugins/platforms/wayland/plugins/shellintegration/xdg-shell/qwaylandxdgshell.cpp

@@ -376,6 +376,7 @@ void QWaylandXdgSurface::xdg_surface_configure(uint32_t serial)
     if (!m_configured) {
         // We have to do the initial applyConfigure() immediately, since that is the expose.
         applyConfigure();
+        m_exposeRegion = QRegion(QRect(QPoint(), m_window->geometry().size()));
     } else {
         // Later configures are probably resizes, so we have to queue them up for a time when we
         // are not painting to the window.