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;;; xdg.el --- XDG specification and standard support -*- lexical-binding: t -*-
;; Copyright (C) 2017 Free Software Foundation, Inc.
;; Author: Mark Oteiza <mvoteiza@udel.edu>
;; Created: 27 January 2017
;; Keywords: files, data
;; This file is part of GNU Emacs.
;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published
;; by the Free Software Foundation; either version 3 of the License,
;; or (at your option) any later version.
;; GNU Emacs 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 License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; Library providing some convenience functions for the following XDG
;; standards and specifications
;;
;; - XDG Base Directory Specification
;; - Thumbnail Managing Standard
;; - xdg-user-dirs configuration
;; - Desktop Entry Specification
;;; Code:
(eval-when-compile
(require 'subr-x))
;; XDG Base Directory Specification
;; https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
(defmacro xdg--dir-home (environ default-path)
(declare (debug (stringp stringp)))
(let ((env (make-symbol "env")))
`(let ((,env (getenv ,environ)))
(if (or (null ,env) (not (file-name-absolute-p ,env)))
(expand-file-name ,default-path)
,env))))
(defun xdg-config-home ()
"Return the base directory for user specific configuration files."
(xdg--dir-home "XDG_CONFIG_HOME" "~/.config"))
(defun xdg-cache-home ()
"Return the base directory for user specific cache files."
(xdg--dir-home "XDG_CACHE_HOME" "~/.cache"))
(defun xdg-data-home ()
"Return the base directory for user specific data files."
(xdg--dir-home "XDG_DATA_HOME" "~/.local/share"))
(defun xdg-runtime-dir ()
"Return the value of $XDG_RUNTIME_DIR."
(getenv "XDG_RUNTIME_DIR"))
(defun xdg-config-dirs ()
"Return the config directory search path as a list."
(let ((env (getenv "XDG_CONFIG_DIRS")))
(if (or (null env) (string= env ""))
'("/etc/xdg")
(parse-colon-path env))))
(defun xdg-data-dirs ()
"Return the data directory search path as a list."
(let ((env (getenv "XDG_DATA_DIRS")))
(if (or (null env) (string= env ""))
'("/usr/local/share/" "/usr/share/")
(parse-colon-path env))))
;; Thumbnail Managing Standard
;; https://specifications.freedesktop.org/thumbnail-spec/thumbnail-spec-latest.html
(defun xdg-thumb-uri (filename)
"Return the canonical URI for FILENAME.
If FILENAME has absolute file name /foo/bar.jpg, its canonical URI is
file:///foo/bar.jpg"
(concat "file://" (expand-file-name filename)))
(defun xdg-thumb-name (filename)
"Return the appropriate thumbnail filename for FILENAME."
(concat (md5 (xdg-thumb-uri filename)) ".png"))
(defun xdg-thumb-mtime (filename)
"Return modification time of FILENAME as an Emacs timestamp."
(file-attribute-modification-time (file-attributes filename)))
;; XDG User Directories
;; https://www.freedesktop.org/wiki/Software/xdg-user-dirs/
(defconst xdg-line-regexp
(eval-when-compile
(rx "XDG_"
(group-n 1 (or "DESKTOP" "DOWNLOAD" "TEMPLATES" "PUBLICSHARE"
"DOCUMENTS" "MUSIC" "PICTURES" "VIDEOS"))
"_DIR=\""
(group-n 2 (or "/" "$HOME/") (*? (or (not (any "\"")) "\\\"")))
"\""))
"Regexp matching non-comment lines in xdg-user-dirs config files.")
(defvar xdg-user-dirs nil
"Alist of directory keys and values.")
(defun xdg--substitute-home-env (str)
(if (file-name-absolute-p str) str
(save-match-data
(and (string-match "^$HOME/" str)
(replace-match "~/" t nil str 0)))))
(defun xdg--user-dirs-parse-line ()
"Return pair of user-dirs key to directory value in LINE, otherwise nil.
This should be called at the beginning of a line."
(skip-chars-forward "[:blank:]")
(when (and (/= (following-char) ?#)
(looking-at xdg-line-regexp))
(let ((k (match-string 1))
(v (match-string 2)))
(when (and k v) (cons k (xdg--substitute-home-env v))))))
(defun xdg--user-dirs-parse-file (filename)
"Return alist of xdg-user-dirs from FILENAME."
(let (elt res)
(when (file-readable-p filename)
(with-temp-buffer
(insert-file-contents filename)
(goto-char (point-min))
(while (not (eobp))
(setq elt (xdg--user-dirs-parse-line))
(when (consp elt) (push elt res))
(forward-line))))
res))
(defun xdg-user-dir (name)
"Return the directory referred to by NAME."
(when (null xdg-user-dirs)
(setq xdg-user-dirs
(xdg--user-dirs-parse-file
(expand-file-name "user-dirs.dirs" (xdg-config-home)))))
(let ((dir (cdr (assoc name xdg-user-dirs))))
(when dir (expand-file-name dir))))
;; Desktop Entry Specification
;; https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-1.1.html
(defconst xdg-desktop-group-regexp
(rx "[" (group-n 1 (+? (in " -Z\\^-~"))) "]")
"Regexp matching desktop file group header names.")
;; TODO Localized strings left out intentionally, as Emacs has no
;; notion of l10n/i18n
(defconst xdg-desktop-entry-regexp
(rx (group-n 1 (+ (in "A-Za-z0-9-")))
;; (? "[" (group-n 3 (+ nonl)) "]")
(* blank) "=" (* blank)
(group-n 2 (* nonl)))
"Regexp matching desktop file entry key-value pairs.")
(defun xdg-desktop-read-group ()
"Return hash table of group of desktop entries in the current buffer."
(let ((res (make-hash-table :test #'equal)))
(while (not (or (eobp) (looking-at xdg-desktop-group-regexp)))
(skip-chars-forward "[:blank:]")
(cond
((eolp))
((= (following-char) ?#))
((looking-at xdg-desktop-entry-regexp)
(puthash (match-string 1) (match-string 2) res))
;; Filter localized strings
((looking-at (rx (group-n 1 (+ (in alnum "-"))) (* blank) "[")))
(t (error "Malformed line: %s"
(buffer-substring (point) (point-at-eol)))))
(forward-line))
res))
(defun xdg-desktop-read-file (filename &optional group)
"Return group contents of desktop file FILENAME as a hash table.
Optional argument GROUP defaults to the string \"Desktop Entry\"."
(with-temp-buffer
(insert-file-contents-literally filename)
(goto-char (point-min))
(while (and (skip-chars-forward "[:blank:]" (line-end-position))
(or (eolp) (= (following-char) ?#)))
(forward-line))
(unless (looking-at xdg-desktop-group-regexp)
(error "Expected group name! Instead saw: %s"
(buffer-substring (point) (point-at-eol))))
(when group
(while (and (re-search-forward xdg-desktop-group-regexp nil t)
(not (equal (match-string 1) group)))))
(forward-line)
(xdg-desktop-read-group)))
(defun xdg-desktop-strings (value)
"Partition VALUE into elements delimited by unescaped semicolons."
(let (res)
(setq value (string-trim-left value))
(dolist (x (split-string (replace-regexp-in-string "\\\\;" "\0" value) ";"))
(push (replace-regexp-in-string "\0" ";" x) res))
(when (null (string-match-p "[^[:blank:]]" (car res))) (pop res))
(nreverse res)))
(provide 'xdg)
;;; xdg.el ends here
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