ivi-shell: unmap views which are not in scenegraph

From Michael Olbrich:
"Both the core in weston_compositor_build_view_list() with view.link
and the ivi-shell in commit_screen_list() with view.layer_link
don't remove the old views from the list.

As a result, all views that are not currently in the list have
old broken links. Destroying such a view tries to remove
the view from these lists and will access the old, invalid pointers."

Therefore, we have to unmap weston_views which are not in current
scenegraph of ivi-shell. I implemented ivi_view_is_mapped() function
to check mappedness of ivi_views. The functions checks:
   - the view is on a layer's order list
   - the layer is on a screen
   - the layer and view's ivi_surface are visible

If ivi_view is not mapped but weston_view is still mapped,
we have to unmap the weston_view with weston_view_unmap() call.

Reported-by: Michael Olbrich <m.olbrich@pengutronix.de>
Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>

ivi-shell/ivi-layout.c

@@ -586,6 +586,15 @@ update_prop(struct ivi_layout_view *ivi_view)
 	weston_view_schedule_repaint(ivi_view->view);
 }
 
+static bool
+ivi_view_is_mapped(struct ivi_layout_view *ivi_view)
+{
+	return (!wl_list_empty(&ivi_view->order_link) &&
+		ivi_view->on_layer->on_screen &&
+		ivi_view->on_layer->prop.visibility &&
+		ivi_view->ivisurf->prop.visibility);
+}
+
 static void
 commit_changes(struct ivi_layout *layout)
 {
@@ -816,6 +825,14 @@ build_view_list(struct ivi_layout *layout)
 	struct ivi_layout_layer   *ivilayer;
 	struct ivi_layout_view   *ivi_view;
 
+	/* If ivi_view is not part of the scenegrapgh, we have to unmap
+	 * weston_views
+	 */
+	wl_list_for_each(ivi_view, &layout->view_list, link) {
+		if (!ivi_view_is_mapped(ivi_view))
+			weston_view_unmap(ivi_view->view);
+	}
+
 	/* Clear view list of layout ivi_layer */
 	wl_list_init(&layout->layout_layer.view_list.link);