Org mode column view dependent columns?

Question

I plan & track my holidays in an Org mode file. In it I use Column View to get a quick overview of what I've planned so far, so that I know how many days I've got left. I use this column setup:

#+COLUMNS: %TIMESTAMP(When) %ITEM(What) %Confirmed(Confirmed?){X/} %Days{+}
#+Confirmed_ALL: "[ ]" "[X]"

It shows a table something like this:

| When                               | What                          | Confirmed? | Days |
|------------------------------------+-------------------------------+------------+------|
|                                    | * Holiday                     | [2/3]      |   14 |
| <2017-02-20 Mon>--<2017-03-01 Wed> | ** Picking fights with bears  | [X]        |    8 |
| <2017-05-04 Thu>--<2017-05-09 Tue> | ** Give bear-fighting lessons | [X]        |    3 |
| <2017-05-10 Wed>--<2017-05-12 Fri> | ** Lick wounds                | [ ]        |    3 |

Is there a way to make the {+} only add up the days that are confirmed? I'd like to make the table look something like this:

| When                               | What                          | Confirmed? | Confirmed Days | Days |
|------------------------------------+-------------------------------+------------+----------------+------|
|                                    | * Holiday                     | [2/3]      |             11 |   14 |
| <2017-02-20 Mon>--<2017-03-01 Wed> | ** Picking fights with bears  | [X]        |              8 |    8 |
| <2017-05-04 Thu>--<2017-05-09 Tue> | ** Give bear-fighting lessons | [X]        |              3 |    3 |
| <2017-05-10 Wed>--<2017-05-12 Fri> | ** Lick wounds                | [ ]        |                |    3 |

Any help appreciated!

Answer 1

I ended up adding the ability to do this as a feature to Org mode. It is available in Org 9.2 (and perhaps earlier). It's a bit too obscure to be documented in the manual, but essentially org-columns-summary-types entries can take an optional COLLECT function now.

You can use this to make collection of a property from an entry conditional on another entry. E.g. given this configuration:

(defun custom/org-collect-confirmed (property)
  "Return `PROPERTY' for `CONFIRMED' entries"
  (let ((prop (org-entry-get nil property))
    (confirmed (org-entry-get nil "CONFIRMED")))
    (if (and prop (string= "[X]" confirmed))
    prop
      "0")))

(setq org-columns-summary-types
      '(("X+" org-columns--summary-sum
     custom/org-collect-confirmed)))

You can have a file bananas.org containing:

#+columns: %ITEM %CONFIRMED %Bananas{+} %Bananas(Confirmed Bananas){X+}

* All shipments
** Shipment 1
   :PROPERTIES:
   :CONFIRMED: [X]
   :Bananas:  4
   :END:

** Shipment 2
   :PROPERTIES:
   :CONFIRMED: [ ]
   :BANANAS:  7
   :END:

… and when going to the top of that file and entering column view you should expect to see something like:

| ITEM          | CONFIRMED | Bananas | Confirmed Bananas |
|---------------+-----------+---------+-------------------|
| All shipments |           |      11 |                 4 |
| Shipment 1    | [X]       |       4 |                 4 |
| Shipment 2    | [ ]       |       7 |                 7 |