Displaying submenus in custom taxonomy of active parent

[nick4fake]

In a hierarchical taxonomy, if a top level item in the hierarchy is selected when editing a post, after save that item's orphaned children and grandchildren will also show as top level items. It flattens the hierarchy.

Here is my hierarchy:

After Selecting "Top Level 2" and saving:

Reproduced in 3.0, so not a new bug. How hierarchical taxonomies are displayed might need a rethink.

I have added and attachment (16475.patch) that changes the way the categories are displayed. Its a proposed solution for the problem. The hierarchy will remain intact after a save, and it will sort the categories putting the checked ones at the top. When sorting, higher levels have priority over lower levels.

For instance in the above example if you would check 'Top Level 2' and 'Foo Child2' and 'foo grandchild', you would get the following hierarchy after saving.

[x]Top Level 2

[x]Foo Child2

[ ]Foo Child

[x]foo grandchild

[ ]Top Level 2

The downside to this way of displaying the categories is that there is a bigger chance that they are not all shown after loading the page. The user might have to scroll.

The code above isn't 100% correct. I will fix the mistake and put the new version here later.

The second patch does not contain any problems anymore.