Help: meaning of the panelize command in left/right menus

[cri at linux.it]

On Wed, Feb 15, 2017 at 04:27:42AM +0200, Mooffie wrote:
> 
> I believe you opened a ticket for this. Please also link to the ticket

Well, yes: http://midnight-commander.org/ticket/3767

> or we'll have two crowds discussing this independently and therefore
> wasting their time.

In fact, that was more a help request than a bug report: I really can't make sense
of that menu item, so I think there's nothing much to "discuss", rather to explain
what the menu command is supposed to do.

Anyway, I did my homework and had a look at the source. 

The menu item is defined in src/filemanager/midnight.c and calls CK_Panelize,
which calls cd_panelize_cmd(), defined in src/filemanager/panelize.c,
which calls do_panelize_cd() (defined in the same file).

Unfortunately I don't know enough C and the mc codebase to understand what
do_panelize_cd() actually does, and there are no comments in the source code. :(

So I browsed the trac history of src/filemanager/panelize.c and found that
do_panelize_cd() was introduced in this commit:

  http://midnight-commander.org/changeset/5c252726f1b52863a75b0118603a0e053923eded

which claims to fix this bug:

  http://midnight-commander.org/ticket/275

The discussion in the ticket deals almost uniquely with adding a ".." entry to the
panelized panel list, to get out of panelized mode; no references to the "Panelize"
Left/Right menu entry.

The commit message for the commit linked above in fact claims:

  "added menu entry Left\Panelize, to restore panelized panel"

but I still can't understand what "restore panelized panel" means
(indeed: all that command seems to do is to show an empty panelized panel).

So that's all the information I could squeeze from the source and trac.

I hope some developer can have a look at
http://midnight-commander.org/browser/src/filemanager/panelize.c
and explain what cd_panelize_cmd() and do_panelize_cd() do.

Cri