emacs: Add interface for package locations.

* emacs/guix-main.scm (%package-location-param-alist): New variable.
(package-location->sexp, package-location-entries): New procedures.
* emacs/guix-ui-location.el: New file.
* emacs.am (ELFILES): Add it.
* doc/emacs.texi (Emacs Package Locations): Document 'guix-locations'.
* NEWS: Mention it.

NEWS

@@ -10,6 +10,12 @@ Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 
 Please send Guix bug reports to bug-guix@gnu.org.
 
+* Changes in 0.11.0 (since 0.10.0)
+
+** Package management
+
+*** New Emacs interface for package locations: M-x guix-locations
+
 * Changes in 0.10.0 (since 0.9.0)
 
 ** Community

doc/emacs.texi

@@ -556,6 +556,13 @@ get lost in these locations:
 
 @table @kbd
 
+@item M-x guix-locations
+Display a list of package locations.  You can press @key{RET} there to
+display packages placed in the current location in the same way as
+@kbd{M-x guix-packages-by-location} would do (@pxref{Emacs Commands}).
+Note that when the point is on a location button, @key{RET} will open
+this location file.
+
 @item M-x guix-find-location
 Open the given package definition source file (press @key{TAB} to choose
 a location from a completion list).

emacs.am

@@ -49,6 +49,7 @@ ELFILES =					\
   emacs/guix-read.el				\
   emacs/guix-ui.el				\
   emacs/guix-ui-license.el			\
+  emacs/guix-ui-location.el			\
   emacs/guix-ui-package.el			\
   emacs/guix-ui-generation.el			\
   emacs/guix-ui-system-generation.el		\

emacs/guix-main.scm

@@ -1127,3 +1127,15 @@ (define-values (packages-by-location-file
      (lambda ()
        "Return the list of file names of all package locations."
        (force files)))))
+
+(define %package-location-param-alist
+  `((id       . ,identity)
+    (location . ,identity)
+    (number-of-packages . ,(lambda (location)
+                             (length (packages-by-location-file location))))))
+
+(define package-location->sexp
+  (object-transformer %package-location-param-alist))
+
+(define (package-location-entries)
+  (map package-location->sexp (package-location-files)))

emacs/guix-ui-location.el

@@ -0,0 +1,83 @@
+;;; guix-ui-location.el --- Interface for displaying package locations
+
+;; Copyright © 2016 Alex Kost <alezost@gmail.com>
+
+;; This file is part of GNU Guix.
+
+;; GNU Guix is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public Location as published by
+;; the Free Software Foundation, either version 3 of the Location, or
+;; (at your option) any later version.
+
+;; GNU Guix is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public Location for more details.
+
+;; You should have received a copy of the GNU General Public Location
+;; along with this program.  If not, see <http://www.gnu.org/locations/>.
+
+;;; Commentary:
+
+;; This file provides a 'list' interface for displaying locations of Guix
+;; packages.
+
+;;; Code:
+
+(require 'guix-buffer)
+(require 'guix-list)
+(require 'guix-location)
+(require 'guix-backend)
+
+(guix-define-entry-type location)
+
+(defun guix-location-get-entries ()
+  "Receive 'package location' entries."
+  (guix-eval-read "(package-location-entries)"))
+
+
+;;; Location 'list'
+
+(guix-list-define-interface location
+  :buffer-name "*Guix Package Locations*"
+  :get-entries-function 'guix-location-get-entries
+  :format '((location guix-location-list-file-name-specification 50 t)
+            (number-of-packages nil 10 guix-list-sort-numerically-1
+                                :right-align t))
+  :sort-key '(location))
+
+(let ((map guix-location-list-mode-map))
+  (define-key map (kbd "RET") 'guix-location-list-show-packages)
+  ;; "Location Info" buffer is not defined (it would be useless), so
+  ;; unbind "i" key (by default, it is used to display Info buffer).
+  (define-key map (kbd "i") nil))
+
+(defun guix-location-list-file-name-specification (location &optional _)
+  "Return LOCATION button specification for `tabulated-list-entries'."
+  (list location
+        'face 'guix-list-file-name
+        'action (lambda (btn)
+                  (guix-find-location (button-get btn 'location)))
+        'follow-link t
+        'help-echo (concat "Find location: " location)
+        'location location))
+
+(declare-function guix-packages-by-location "guix-ui-package")
+
+(defun guix-location-list-show-packages ()
+  "Display packages placed in the location at point."
+  (interactive)
+  (guix-packages-by-location (guix-list-current-id)))
+
+
+;;; Interactive commands
+
+;;;###autoload
+(defun guix-locations ()
+  "Display locations of the Guix packages."
+  (interactive)
+  (guix-list-get-display-entries 'location))
+
+(provide 'guix-ui-location)
+
+;;; guix-ui-location.el ends here