[syslinux] DEFAULT versus UI

[Gene Cumm]

I'm posting this as I'm trying to evaluate DEFAULT versus UI.

As it stands right now, the use of the UI directive means that DEFAULT
is effectively ignored from the command line.  If you specify UI and
DEFAULT and use (vesa)menu.c32, (vesa)menu.c32 will use DEFAULT unless
a MENU DEFAULT option exist in the current context.  If the attempt to
execute a command fails, returning you to the "boot: " prompt, hitting
enter will return you to the menu (assuming you haven't switched
configs).  If your specified UI does not exist, hitting enter will
again attempt to load the UI (probably unsuccessfully unless it's
PXELINUX and you encountered an error that won't repeat on a
particular retry).

If you've specified UI and DEFAULT but the UI file can not be found or
otherwise loaded from media completely, I think it would be more
advantageous to the user to return an error stating (probably in
addition to the existing output) "UI could not be loaded" and then
hitting enter at "boot: " would activate DEFAULT rather than failing
again on UI.  Alternatively, it could again attempt to load UI but on
failure, run DEFAULT.  However, if loading UI was successful, hitting
enter from the "boot: " prompt should return to the menu.

Thoughts/comments?

HPA, I'm interested in working on this if there's interest.

-- 
-Gene