[libdazzle] menu-manager: implement reverse position dependencies

[Christian Hergert <chergert src gnome org>]

commit a22f5fc0e6b0d7fdcead98a39cbd0823bf2de337
Author: Christian Hergert <chergert redhat com>
Date:   Sat Jul 8 14:56:24 2017 -0700

    menu-manager: implement reverse position dependencies
    
    If we have previous menu items in the model that are trying
    to position themselves with respect to the newly inserting
    item, we need to take those positions into account with the
    sort order.

 src/menus/dzl-menu-manager.c |   52 +++++++++++++++++++++++++++++++++++++-----
 1 files changed, 46 insertions(+), 6 deletions(-)
---
diff --git a/src/menus/dzl-menu-manager.c b/src/menus/dzl-menu-manager.c
index 1e22dd9..3b1a1af 100644
--- a/src/menus/dzl-menu-manager.c
+++ b/src/menus/dzl-menu-manager.c
@@ -168,14 +168,19 @@ static gint
 find_position_for_item (GMenuModel *model,
                         GMenuItem  *item)
 {
+  g_autofree gchar *label = NULL;
+  g_autofree gchar *id = NULL;
   const gchar *after;
   const gchar *before;
+  gint n_items;
   gint before_pos = -1;
   gint after_pos = -1;
 
   g_assert (G_IS_MENU_MODEL (model));
   g_assert (G_IS_MENU_ITEM (item));
 
+  n_items = g_menu_model_get_n_items (model);
+
   if (!g_menu_item_get_attribute (item, DZL_MENU_ATTRIBUTE_AFTER, "&s", &after))
     after = NULL;
 
@@ -202,14 +207,49 @@ find_position_for_item (GMenuModel *model,
     }
 
   /*
-   * TODO: Perform resort after all items have been inserted.
-   *
-   *       We cannot resolve all positions incrementally as we add them since
-   *       plugin ordering cannot be guaranteed (and some relative positions
-   *       may not yet be available). If relations were symmetrical, that
-   *       wouldn't be a problem.
+   * Now that we've positioned ourselves within the range we care about,
+   * we need to see if any item within that range has reverse-preferences
+   * about their position related to us.
    */
 
+  if (!g_menu_item_get_attribute (item, "id", "s", &id))
+    id = NULL;
+
+  if (!g_menu_item_get_attribute (item, G_MENU_ATTRIBUTE_LABEL, "s", &label))
+    label = NULL;
+
+  for (gint i = 0; i < n_items; i++)
+    {
+      g_autofree gchar *item_before = NULL;
+      g_autofree gchar *item_after = NULL;
+
+      if (g_menu_model_get_item_attribute (model, i, "before", "s", &item_before))
+        {
+          /* If this item requires it is before us, we need to ensure we
+           * come after this position.
+           */
+          if ((item_before && id && g_strcmp0 (item_before, id) == 0) ||
+              (item_before && label && g_strcmp0 (item_before, label) == 0))
+            {
+              if (after_pos == -1 || after_pos < i)
+                after_pos = i;
+            }
+        }
+
+      if (g_menu_model_get_item_attribute (model, i, "after", "s", &item_after))
+        {
+          /* If this item requires it is after us, we need to ensure we
+           * come before this position.
+           */
+          if ((item_after && id && g_strcmp0 (item_after, id) == 0) ||
+              (item_after && label && g_strcmp0 (item_after, label) == 0))
+            {
+              if (before_pos == -1 || before_pos > i)
+                before_pos = i;
+            }
+        }
+    }
+
   if (before_pos >= 0)
     return MAX (0, before_pos - 1);