From b48e158ef8e7da35dcf646fa35f62f78683c896c Mon Sep 17 00:00:00 2001
From: Emmanuele Bassi <ebassi@gnome.org>
Date: Tue, 24 Aug 2021 01:11:15 +0100
Subject: [PATCH] Release an extra reference on GtkExpander:child

The child of a GtkExpander is owned directly by the expander whenever
the "expanded" flag is unset.

We are adding an additional reference to the child of an expander when
expander is not expanded.

Additionally, if a GtkExpander is disposed while not expanded, we need
to explicitly release the reference on the child widget that we own.

This reference leak was masked in GTK3 by GtkContainer removing each
child from the parent container by recursively calling
gtk_widget_destroy().
---
 gtk/gtkexpander.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/gtk/gtkexpander.c b/gtk/gtkexpander.c
index 00b9a52e38..27d94b0112 100644
--- a/gtk/gtkexpander.c
+++ b/gtk/gtkexpander.c
@@ -582,6 +582,10 @@ gtk_expander_dispose (GObject *object)
       expander->expand_timer = 0;
     }
 
+  /* If the expander is not expanded, we own the child */
+  if (!expander->expanded)
+    g_clear_object (&expander->child);
+
   if (expander->box)
     {
       gtk_widget_unparent (expander->box);
@@ -900,6 +904,9 @@ gtk_expander_set_expanded (GtkExpander *expander,
 
   if (child)
     {
+      /* Transfer the ownership of the child to the box when
+       * expanded is set, and then back to us when it is unset
+       */
       if (expander->expanded)
         {
           gtk_box_append (GTK_BOX (expander->box), child);
@@ -1196,25 +1203,31 @@ gtk_expander_set_child (GtkExpander *expander,
   g_return_if_fail (GTK_IS_EXPANDER (expander));
   g_return_if_fail (child == NULL || GTK_IS_WIDGET (child));
 
+  if (expander->child == child)
+    return;
+
   if (expander->child)
     {
-      gtk_box_remove (GTK_BOX (expander->box), expander->child);
       if (!expander->expanded)
         g_object_unref (expander->child);
+      else
+        gtk_box_remove (GTK_BOX (expander->box), expander->child);
     }
 
   expander->child = child;
 
   if (expander->child)
     {
+      /* We only add the child to the box if the expander is
+       * expanded; otherwise we just claim ownership of the
+       * child by sinking its floating reference, or acquiring
+       * an additional reference to it. The reference will be
+       * dropped once the expander is expanded
+       */
       if (expander->expanded)
         gtk_box_append (GTK_BOX (expander->box), expander->child);
       else
-        {
-          if (g_object_is_floating (expander->child))
-            g_object_ref_sink (expander->child);
-          g_object_ref (expander->child);
-        }
+        g_object_ref_sink (expander->child);
 
       gtk_accessible_update_relation (GTK_ACCESSIBLE (expander),
                                       GTK_ACCESSIBLE_RELATION_CONTROLS, expander->child, NULL,
-- 
2.30.2