[gtk/inspector-trees: 1/2] Add gtk_css_node_observe_children

[Matthias Clasen <matthiasc src gnome org>]

commit f8357512d028cf123ae4cb07103d782732db4329
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Oct 7 15:51:02 2022 -0400

    Add gtk_css_node_observe_children

 gtk/gtkcssnode.c        | 41 +++++++++++++++++++++++++++++++++++++++++
 gtk/gtkcssnodeprivate.h |  5 +++++
 2 files changed, 46 insertions(+)
---
diff --git a/gtk/gtkcssnode.c b/gtk/gtkcssnode.c
index b092da15a8..db53aee187 100644
--- a/gtk/gtkcssnode.c
+++ b/gtk/gtkcssnode.c
@@ -241,6 +241,9 @@ gtk_css_node_dispose (GObject *object)
 
   g_clear_pointer (&cssnode->cache, gtk_css_node_style_cache_unref);
 
+ if (cssnode->children_observer)
+   gtk_list_list_model_clear (cssnode->children_observer);
+
   G_OBJECT_CLASS (gtk_css_node_parent_class)->dispose (object);
 }
 
@@ -506,6 +509,9 @@ gtk_css_node_real_node_removed (GtkCssNode *parent,
   node->previous_sibling = NULL;
   node->next_sibling = NULL;
   node->parent = NULL;
+
+  if (parent->children_observer)
+    gtk_list_list_model_item_removed (parent->children_observer, previous);
 }
 
 static void
@@ -713,10 +719,13 @@ gtk_css_node_reposition (GtkCssNode *node,
                          GtkCssNode *previous)
 {
   GtkCssNode *old_parent;
+  GtkCssNode *old_previous;
 
   g_assert (! (new_parent == NULL && previous != NULL));
 
   old_parent = node->parent;
+  old_previous = node->previous_sibling;
+
   /* Take a reference here so the whole function has a reference */
   g_object_ref (node);
 
@@ -801,6 +810,14 @@ gtk_css_node_reposition (GtkCssNode *node,
                                  | (node->previous_sibling ? 0 : GTK_CSS_CHANGE_FIRST_CHILD)
                                  | (node->next_sibling ? 0 : GTK_CSS_CHANGE_LAST_CHILD));
 
+  if (new_parent && new_parent->children_observer)
+    {
+      if (old_previous)
+        gtk_list_list_model_item_moved (new_parent->children_observer, node, old_previous);
+      else
+        gtk_list_list_model_item_added (new_parent->children_observer, node);
+    }
+
   g_object_unref (node);
 }
 
@@ -1442,3 +1459,27 @@ gtk_css_node_print (GtkCssNode                *cssnode,
         gtk_css_node_print (node, flags, string, indent + 2);
     }
 }
+
+static void
+gtk_css_node_child_observer_destroyed (gpointer cssnode)
+{
+  GTK_CSS_NODE (cssnode)->children_observer = NULL;
+}
+
+GListModel *
+gtk_css_node_observe_children (GtkCssNode *cssnode)
+{
+  if (cssnode->children_observer)
+    return g_object_ref (G_LIST_MODEL (cssnode->children_observer));
+
+  cssnode->children_observer = gtk_list_list_model_new ((gpointer) gtk_css_node_get_first_child,
+                                                        (gpointer) gtk_css_node_get_next_sibling,
+                                                        (gpointer) gtk_css_node_get_previous_sibling,
+                                                        (gpointer) gtk_css_node_get_last_child,
+                                                        (gpointer) g_object_ref,
+                                                        cssnode,
+                                                        gtk_css_node_child_observer_destroyed);
+
+  return G_LIST_MODEL (cssnode->children_observer);
+}
+
diff --git a/gtk/gtkcssnodeprivate.h b/gtk/gtkcssnodeprivate.h
index ae07da00cb..e696ec49bc 100644
--- a/gtk/gtkcssnodeprivate.h
+++ b/gtk/gtkcssnodeprivate.h
@@ -25,6 +25,7 @@
 #include "gtkbitmaskprivate.h"
 #include "gtkcsstypesprivate.h"
 #include "gtkstylecontext.h"
+#include "gtklistlistmodelprivate.h"
 
 G_BEGIN_DECLS
 
@@ -47,6 +48,8 @@ struct _GtkCssNode
   GtkCssNode *first_child;
   GtkCssNode *last_child;
 
+  GtkListListModel *children_observer;
+
   GtkCssNodeDeclaration *decl;
   GtkCssStyle           *style;
   GtkCssNodeStyleCache  *cache;                 /* cache for children to look up styles */
@@ -157,6 +160,8 @@ void                    gtk_css_node_print              (GtkCssNode
                                                          GString                   *string,
                                                          guint                      indent);
 
+GListModel *            gtk_css_node_observe_children   (GtkCssNode                *cssnode);
+
 G_END_DECLS
 
 #endif /* __GTK_CSS_NODE_PRIVATE_H__ */