This file contains random notes on the implementation of a shell name space
extension.

The shareui name space extension mostly independent of the shell, and only uses
a few shell interfaces that are internal, particularly the standard shell
folder view, using SHCreateShellFolderViewEx.

Menus
=================================================
Menus appear in several places:
1. Context-menus on a selection
2. Context-menu on the background
3. The menu bar, with a selection
4. The menu bar, with nothing selected

=======
For (1), the menu is:

    Delete
    ------
    Properties

and the default is Properties. Properties is grayed if there is more than one
item selected.

=======
For (2), the menu is the standard shell folder view menu, plus a "New" item:

    View
        Large Icons
        Small Icons
        List
        Details
    -------
    Arrange Icons
        by Name
        by Comment
        by Max Uses         -- only for administrators
        by Current Uses     -- only for administrators
        by Path             -- only for administrators
        -------
        Auto Arrange
    Line up Icons
    -------
    Paste                   -- always grayed
    Paste Shortcut          -- always grayed
    -------
    New
        Share

=======
For (3), the File menu should be:

    New
        Share
    -------
    Create Shortcut         -- always grayed
    Delete
    Rename                  -- always grayed
    Properties
    -------
    Close

and the View->Arrange Icons menu should be:

    by Name
    by Comment
    by Max Uses         -- only for administrators
    by Current Uses     -- only for administrators
    by Path             -- only for administrators
    -------
    Auto Arrange

As with (1), Properties will be the default, and will be grayed if the
selection includes more than one item.

=======
For (4), the File menu should be:

    New
        Share
    -------
    Create Shortcut         -- always grayed
    Delete                  -- grayed
    Rename                  -- always grayed
    Properties              -- grayed
    -------
    Close

and the View->Arrange Icons menu should be the same as in (3).

=======
The implementation for these various menus occurs in several different places
and should be synchronized to make sure the menus all do the same thing.

Case (1) is implemented by the shell calling IShellFolder::GetUIObjectOf asking
for IContextMenu.

Case (2) is implemented by the shell calling IShellFolder::CreateViewObject
asking for IContextMenu.

Case (3) is implemented by the shell calling IShellFolder::GetUIObjectOf asking
for IContextMenu. The context-menu is created. Also, the ...?

Case (4) is implemented as follows. When a shell folder view created using
SHCreateShellFolderViewEx is created, it calls back the passed-in callback
function with the message DVM_MERGEMENU. At this point, the background menus
are created.

The IContextMenu interfaces are also invoked for other uses, namely performing operations from the toolbar. The toolbar calls IShellFolder::GetUIObjectOf
asking for IContextMenu when it needs to call properties or delete an item.
It calls IContextMenu::InvokeCommand with string commands "delete" or
"properties" in these cases.