Dynamically modifying menu entries

Dynamically modifying menu entries

[Michael Mauger]

I am building a menu using `easy-menu-define' with a submenu whose entries are 
dependent on the entries in a list in the package.  The contents of the list may 
change and based on those changes the contents of the submenu may change.  This 
is not as simple as enabling/disabling menu entries; it involves adding and 
removing entries based on the contents of the separate list.

I have one submenu for which I have a separate API to maintain the list and 
corresponding submenu contents.  In another case, the API feels like overkill.

I've tried the :filter function and rather than filtering out existing menu 
entries I return an augmented list of entries.  It worked on Gnome but I'm not 
sure that it is an appropriate way of dynamically populating a submenu.  It also 
does appear that the submenu doesn't get refreshed as frequently as I'd like.  
Ideally, I'd like to be able to populate the submenu when it's selected rather 
than having to predefine the menu contents.

What am I missing, or is using the :filter handler the way to go? 

TIA

RE: Dynamically modifying menu entries

[Drew Adams]

> I am building a menu using `easy-menu-define' with a submenu 
> whose entries are dependent on the entries in a list in the
> package.  The contents of the list may change and based on
> those changes the contents of the submenu may change.  This 
> is not as simple as enabling/disabling menu entries; it 
> involves adding and removing entries based on the contents
> of the separate list.
> 
> I have one submenu for which I have a separate API to 
> maintain the list and corresponding submenu contents.
> In another case, the API feels like overkill.
> 
> I've tried the :filter function and rather than filtering out 
> existing menu entries I return an augmented list of entries.
> It worked on Gnome but I'm not sure that it is an appropriate
> way of dynamically populating a submenu.  It also does appear
> that the submenu doesn't get refreshed as frequently as I'd like.  
> Ideally, I'd like to be able to populate the submenu when 
> it's selected rather than having to predefine the menu contents.
> 
> What am I missing, or is using the :filter handler the way to go? 

I don't know the answer and I'm no expert on easy-menu (or menus generally).
But I would think that you could use `:visible for this (dynamically add/remove
menu items and menus).  Dunno if you can also use `:filter' for it.

My impression from reading the doc is that `:filter' is more about dynamically
calculating the particular binding(s) to use, whereas `:visible' is more about
dynamically choosing whether the item or menu appears at all.  The latter seems
to be what you want to do: determine which items should appear in some given
context.

For `easy-menu', `:filter' and `:visible' apparently apply to a set of menu
items and not to a single menu item (as they do for `menu-item' with
`define-key', for example).

I use `:visible' with `menu-item' (and `define-key') a lot, but I've only used
`:filter' once or twice.  And I don't recall using either of them with
`easy-menu'.

Unless someone can help you based on your description, perhaps it would help if
you gave a concrete example.  It might also be that you've stumbled upon a bug.

Re: Dynamically modifying menu entries

[Stefan Monnier]

> I am building a menu using `easy-menu-define' with a submenu whose
> entries are  dependent on the entries in a list in the package.
> The contents of the list may  change and based on those changes the
> contents of the submenu may change.  This  is not as simple as
> enabling/disabling menu entries; it involves adding and  removing
> entries based on the contents of the separate list.

If the set of possible entries is finite (and reasonably small), then
you can use :visible, but otherwise :filter is most likely the way to go.

> It also  does appear that the submenu doesn't get refreshed as
> frequently as I'd like.  Ideally, I'd like to be able to populate the
> submenu when it's selected rather than having to predefine the
> menu contents.

:filter should be run often enough (or even more often than that, in my
experience), so if it's not often enough for you, please report the
precise case where it fails to be (re)run.


        Stefan