[gtk/ebassi/issue-3892] a11y: Update the level property for tree expanders

[Emmanuele Bassi <ebassi src gnome org>]

commit 8789e787965dbf574b01be8b514c917085039d77
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Apr 22 14:37:39 2021 +0100

    a11y: Update the level property for tree expanders
    
    We already have the depth of a tree expander in order to compute the
    indentation.
    
    Fixes: #3892

 gtk/gtktreeexpander.c | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/gtk/gtktreeexpander.c b/gtk/gtktreeexpander.c
index 4ebc072236..19b577d826 100644
--- a/gtk/gtktreeexpander.c
+++ b/gtk/gtktreeexpander.c
@@ -239,6 +239,11 @@ gtk_tree_expander_update_for_list_row (GtkTreeExpander *self)
             }
         }
 
+      /* The level property is >= 1 */
+      gtk_accessible_update_property (GTK_ACCESSIBLE (self),
+                                      GTK_ACCESSIBLE_PROPERTY_LEVEL, depth + 1,
+                                      -1);
+
       while (child)
         {
           GtkWidget *prev = gtk_widget_get_prev_sibling (child);