boxlayout: Be more careful with what to consider natural size

Don't just use the natural size as the max size, the natural size
is the ideal size, not necessarily the maximum size.

Also check the nat size for opposite min size.

gtk/gtkboxlayout.c

@@ -327,6 +327,8 @@ gtk_box_layout_compute_opposite_size_for_size (GtkBoxLayout *self,
        child != NULL;
        child = _gtk_widget_get_next_sibling (child))
     {
+      int min_opposite, nat_for_min;
+
       if (!gtk_widget_should_layout (child))
         continue;
 
@@ -335,6 +337,22 @@ gtk_box_layout_compute_opposite_size_for_size (GtkBoxLayout *self,
                           -1,
                           &sizes[i].minimum_size, &sizes[i].natural_size,
                           NULL, NULL);
+      /* Don't just use the natural size as the max size,
+       * the natural size is the ideal size, not necessarily
+       * the maximum size.
+       * Also check the nat size for opposite min size.
+       */
+      gtk_widget_measure (child,
+                          OPPOSITE_ORIENTATION (self->orientation),
+                          -1,
+                          &min_opposite, NULL,
+                          NULL, NULL);
+      gtk_widget_measure (child,
+                          self->orientation,
+                          min_opposite,
+                          NULL, &nat_for_min,
+                          NULL, NULL);
+      sizes[i].natural_size = MAX (sizes[i].natural_size, nat_for_min);
 
       children_minimum_size += sizes[i].minimum_size;
       i += 1;