cssnode: Refactor node tree modification code

This allows adding more API for it.

It also includes code that tracks modifications and invalidates siblings
and their positions whenever nodes get added or removed.

2 files changed, 97 insertions, 47 deletions

diff --git a/gtk/gtkcssnode.c b/gtk/gtkcssnode.c
index 816c667d3d..92b165dfa3 100644
--- a/gtk/gtkcssnode.c
+++ b/gtk/gtkcssnode.c
@@ -359,73 +359,118 @@ gtk_css_node_parent_will_be_set (GtkCssNode *node)
     GTK_CSS_NODE_GET_CLASS (node)->dequeue_validate (node);
 }
 
-void
-gtk_css_node_set_parent (GtkCssNode *node,
-                         GtkCssNode *parent)
+static void
+gtk_css_node_unlink_from_siblings (GtkCssNode *node)
 {
-  if (node->parent == parent)
+  if (GTK_IS_CSS_TRANSIENT_NODE (node))
     return;
 
-  /* Take a reference here so the whole function has a reference */
-  g_object_ref (node);
+  if (node->previous_sibling)
+    node->previous_sibling->next_sibling = node->next_sibling;
+  else
+    node->parent->first_child = node->next_sibling;
 
-  if (node->parent != NULL)
+  if (node->next_sibling)
+    node->next_sibling->previous_sibling = node->previous_sibling;
+  else
+    node->parent->last_child = node->previous_sibling;
+
+  node->previous_sibling = NULL;
+  node->next_sibling = NULL;
+}
+
+static void
+gtk_css_node_link_to_siblings (GtkCssNode *node,
+                               GtkCssNode *new_previous)
+{
+  if (GTK_IS_CSS_TRANSIENT_NODE (node))
+    return;
+
+  if (new_previous)
     {
-      if (!GTK_IS_CSS_TRANSIENT_NODE (node))
-        {
-          if (node->previous_sibling)
-            node->previous_sibling->next_sibling = node->next_sibling;
-          else
-            node->parent->first_child = node->next_sibling;
+      node->previous_sibling = new_previous;
+      node->next_sibling = new_previous->next_sibling;
+      new_previous->next_sibling = node;
+    }
+  else
+    {
+      node->next_sibling = node->parent->first_child;
+      node->parent->first_child = node;
+    }
+
+  if (node->next_sibling)
+    node->next_sibling->previous_sibling = node;
+  else
+    node->parent->last_child = node;
+}
 
-          if (node->next_sibling)
-            node->next_sibling->previous_sibling = node->previous_sibling;
-          else
-            node->parent->last_child = node->previous_sibling;
+static void
+gtk_css_node_set_children_changed (GtkCssNode *node)
+{
+  if (node->children_changed)
+    return;
 
-          node->parent->n_children--;
-        }
+  node->children_changed = TRUE;
+  gtk_css_node_set_invalid (node, TRUE);
+}
 
-      node->parent = NULL;
-      node->next_sibling = NULL;
-      node->previous_sibling = NULL;
+static void
+gtk_css_node_reposition (GtkCssNode *node,
+                         GtkCssNode *parent,
+                         GtkCssNode *previous)
+{
+  g_assert (! (parent == NULL && previous != NULL));
 
-      g_object_unref (node);
+  /* Take a reference here so the whole function has a reference */
+  g_object_ref (node);
 
-      if (parent == NULL)
-        gtk_css_node_parent_was_unset (node);
-    }
+  if (node->parent != NULL)
+    gtk_css_node_unlink_from_siblings (node);
 
-  if (parent)
+  if (node->parent != parent)
     {
       if (node->parent == NULL)
-        gtk_css_node_parent_will_be_set (node);
+        {
+          gtk_css_node_parent_will_be_set (node);
+        }
+      else
+        {
+          g_object_unref (node);
+          gtk_css_node_set_children_changed (node->parent);
+        }
 
       node->parent = parent;
 
-      if (!GTK_IS_CSS_TRANSIENT_NODE (node))
+      if (parent)
         {
-          parent->n_children++;
+          gtk_css_node_set_children_changed (parent);
+          g_object_ref (node);
 
-          if (parent->last_child)
-            {
-              parent->last_child->next_sibling = node;
-              node->previous_sibling = parent->last_child;
-            }
-          parent->last_child = node;
-
-          if (parent->first_child == NULL)
-            parent->first_child = node;
+          if (node->invalid)
+            gtk_css_node_set_invalid (parent, TRUE);
+        }
+      else
+        {
+          gtk_css_node_parent_was_unset (node);
         }
-
-      if (node->invalid)
-        gtk_css_node_set_invalid (parent, TRUE);
     }
 
+  if (parent)
+    gtk_css_node_link_to_siblings (node, previous);
+
   gtk_css_node_invalidate (node, GTK_CSS_CHANGE_ANY_PARENT | GTK_CSS_CHANGE_ANY_SIBLING);
 
-  if (node->parent == NULL)
-    g_object_unref (node);
+  g_object_unref (node);
+}
+
+void
+gtk_css_node_set_parent (GtkCssNode *node,
+                         GtkCssNode *parent)
+{
+  if (node->parent == parent)
+    return;
+
+  gtk_css_node_reposition (node, parent, parent ? parent->last_child : NULL);
 }
 
 GtkCssNode *
@@ -638,6 +683,11 @@ gtk_css_node_propagate_pending_changes (GtkCssNode *cssnode)
     return;
 
   change = _gtk_css_change_for_child (cssnode->pending_changes);
+  if (cssnode->children_changed)
+    {
+      change |= GTK_CSS_CHANGE_POSITION | GTK_CSS_CHANGE_ANY_SIBLING;
+      cssnode->children_changed = FALSE;
+    }
 
   for (child = gtk_css_node_get_first_child (cssnode);
        child;
@@ -671,11 +721,11 @@ gtk_css_node_validate (GtkCssNode            *cssnode,
   if (G_UNLIKELY (gtk_get_debug_flags () & GTK_DEBUG_NO_CSS_CACHE))
     change = GTK_CSS_CHANGE_ANY;
 
+  gtk_css_node_propagate_pending_changes (cssnode);
+
   if (!cssnode->invalid && change == 0 && _gtk_bitmask_is_empty (parent_changes))
     return;
 
-  gtk_css_node_propagate_pending_changes (cssnode);
-
   gtk_css_node_set_invalid (cssnode, FALSE);
 
   change = cssnode->pending_changes;
diff --git a/gtk/gtkcssnodeprivate.h b/gtk/gtkcssnodeprivate.h
index 4207d2ff56..b1339b0b9c 100644
--- a/gtk/gtkcssnodeprivate.h
+++ b/gtk/gtkcssnodeprivate.h
@@ -43,7 +43,6 @@ struct _GtkCssNode
   GtkCssNode *next_sibling;
   GtkCssNode *first_child;
   GtkCssNode *last_child;
-  guint n_children;
 
   GtkCssNodeDeclaration *decl;
   GtkCssStyle           *style;
@@ -51,6 +50,7 @@ struct _GtkCssNode
   GtkCssChange           pending_changes;       /* changes that accumulated since the style was last computed */
 
   guint                  invalid :1;            /* node or a child needs to be validated (even if just for animation) */
+  guint                  children_changed :1;   /* the children changed since last validation */
 };
 
 struct _GtkCssNodeClass