sacha chua :: living an awesome life

One of the first things you’ll probably want to change about Emacs is the default face. This controls the foreground color, the background color, the font, and other attributes. For example, many graphical environments give Emacs a background of white. If you prefer a black background (which can be less tiring during long periods of use), you can change the background to black my customizing the default face.

To change the background color and other attributes, use the command M-x customize-face, and specify default as the face to customize. Change the attributes and the sample text will reflect your settings. When you are satisfied, select Save for future sessions. Your changes will be saved to ~/.emacs and reloaded the next time you start the editor.

This is a draft for Wicked Cool Emacs, a book that will be published by No Starch Press. (if we manage to get it all together! =)

Sometimes w3m is not enough. To make it easier to open the current page in a browser such as Mozilla Firefox, add the following to your ~/.emacs:

(defun wicked/w3m-open-current-page-in-firefox ()
  "Open the current URL in Mozilla Firefox."
  (interactive)
  (browse-url-firefox w3m-current-url)) ;; (1)

(defun wicked/w3m-open-link-or-image-in-firefox ()
  "Open the current link or image in Firefox."
  (interactive)
  (browse-url-firefox (or (w3m-anchor) ;; (2)
                          (w3m-image)))) ;; (3)

This defines a function that uses the current URL being browsed(1) and another function that takes the URL of the link at point(2). If no link is found, it takes the URL of the image at point(3).

You can use other browse-url functions instead of browse-url-firefox. For example, replacing browse-url-firefox with browse-url-kde will open the page, link, or image in Konqueror, KDE’s web browser.

I like binding f to the function that opens the current URL in Mozilla Firefox and F to the function that opens the current link or image in Mozilla Firefox. To do the same, add the following to your ~/.emacs:

(eval-after-load 'w3m
  (progn
    (define-key w3m-mode-map "f" 'wicked/w3m-open-current-page-in-firefox)
    (define-key w3m-mode-map "F" 'wicked/w3m-open-link-or-image-in-firefox)))

—
This is part of the book that I’m writing about Emacs, which will be published by No Starch Press if I manage to get it together in time.

If you browse with a lot of open tabs, like I do, w3m will be much easier to use once you remap w3m-next-buffer and w3m-previous-buffer onto single-key shortcuts, allowing you to press a key to quickly flip between tabs.

By default, w3m-previous-buffer is mapped to C-c C-p and w3m-next-buffer is mapped to C-c C-n. On a QWERTY keyboard, you may want to remap w3m-previous-buffer to q and w3m-next-buffer to w. You’ll probably also want to remap w3m-close-window (which had been bound to q), and x is a good keybinding for that. To make all these changes, add the following to your ~/.emacs:

(eval-after-load 'w3m
  '(progn
     (define-key w3m-mode-map "q" 'w3m-previous-buffer)
     (define-key w3m-mode-map "w" 'w3m-next-buffer)
     (define-key w3m-mode-map "x" 'w3m-close-window)))

If you use a Dvorak keyboard layout, you can bind . to w3m-previous-buffer and , to w3m-next-buffer instead. Just add the following code to your ~/.emacs:

(eval-after-load 'w3m
  '(progn
     (define-key w3m-mode-map "." 'w3m-previous-buffer)
     (define-key w3m-mode-map "," 'w3m-next-buffer)))

(This is part of the draft for my book on Emacs, to be published by No Starch Press if I’m not too late.)

Here’s a handy shortcut that toggles between the W3M web browser and other buffers you’re working on. I use it to quickly switch between code and documentation (or your favorite timewasting site, as it also makes a handy boss key).

Define the function by adding the following code to your ~/.emacs:

(defun wicked/toggle-w3m ()
  "Switch to a w3m buffer or return to the previous buffer."
  (interactive)
  (if (derived-mode-p 'w3m-mode)
      ;; Currently in a w3m buffer
      ;; Bury buffers until you reach a non-w3m one
      (while (derived-mode-p 'w3m-mode)
	(bury-buffer))
    ;; Not in w3m
    ;; Find the first w3m buffer
    (let ((list (buffer-list)))
      (while list
	(if (with-current-buffer (car list)
	      (derived-mode-p 'w3m-mode))
	    (progn
	      (switch-to-buffer (car list))
	      (setq list nil))
	  (setq list (cdr list))))
      (unless (derived-mode-p 'w3m-mode)
	(call-interactively 'w3m)))))

Then bind it to a shortcut key sequence (F7 F7 in this example) by adding the following code to your ~/.emacs:

(global-set-key (kbd " ") 'wicked/toggle-w3m)

You can then use F7 F7 to switch back and forth between your web browser and whatever else you’re working on.

In an ideal world, you would never need to make your browser pretend to be a different browser. In reality, a number of websites check for specific browsers such as Mozilla or Internet Explorer, or even specific versions of those browsers. Other websites check for popular search engine crawlers such as the Googlebot in order to display content optimized for that search engine. You may want to change your user agent to work around such limitations, or you might want to change your user agent string just for fun.

The following code allows you to set your user agent (wicked/w3m-set-user-agent), reload the current page using a specified user agent (wicked/w3m-reload-this-page-with-user-agent), and define regular expression matches for URLs to control user agent strings (wicked/w3m-fake-user-agent-sites). To use this, add the following to your ~/.emacs:

 (defvar wicked/w3m-fake-user-agents ;; (1)
   `(("w3m" . ,(concat "Emacs-w3m/" emacs-w3m-version " " w3m-version))
     ("ie6" . "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)")
     ("ff3" . "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.1) Gecko/2008070206 Firefox/3.0.1")
     ("ff2" . "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.13) Gecko/20080208 Firefox/2.0.0.13")
     ("ie7" . "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)")
     ("ie5.5" . "Mozilla/4.0 (compatible; MSIE 5.5; Windows 98)")
     ("iphone" . "Mozilla/5.0 (iPhone; U; CPU iPhone OS 2_0 like Mac OS X; en-us) AppleWebKit/525.18.1 (KHTML, like Gecko) Version/3.1.1 Mobile/5A347 Safari/525.20")
     ("safari" . "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_2; en-us) AppleWebKit/525.13 (KHTML, like Gecko) Version/3.1 Safari/525.13")
     ("google" . "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"))
   "*Associative list of user agent names and strings.")

 (defvar wicked/w3m-fake-user-agent-sites ;; (2)
   '(("^https?://www\\.useragentstring\\.com" . "ff2"))
   "*Associative list of regular expressions matching URLs and the agent keyword or value.
 The first matching entry will be used.")

 (defun wicked/w3m-set-user-agent (agent)
   "Set the user agent to AGENT based on `wicked/w3m-fake-user-agents'.
 If AGENT is not defined in `wicked/w3m-fake-user-agents', it is used as the user agent.
 If AGENT is empty, the default w3m user agent will be used."
   (interactive
    (list
     (completing-read "User-agent [w3m]: "
                    (mapcar 'car wicked/w3m-fake-user-agents)
                    nil nil nil nil "w3m"))) ;; (3)
   (if agent
       (progn
        (setq w3m-user-agent
              (or
               (and (string= agent "") (assoc "w3m" wicked/w3m-fake-user-agents)) ;; (4)
               (cdr (assoc agent wicked/w3m-fake-user-agents)) ;; (5)
               agent)) ;; (6)
        (setq w3m-add-user-agent t))
     (setq w3m-add-user-agent nil)))

 (defun wicked/w3m-reload-this-page-with-user-agent (agent)
   "Browse this page using AGENT based on `wicked/w3m-fake-user-agents'.
 If AGENT is not defined in `wicked/w3m-fake-user-agents', it is used as the user agent.
 If AGENT is empty, the default w3m user agent will be used."
   (interactive (list (completing-read "User-agent [w3m]: "
                    (mapcar 'car wicked/w3m-fake-user-agents)
                    nil nil nil nil "w3m")))
   (let ((w3m-user-agent w3m-user-agent)
       (w3m-add-user-agent w3m-add-user-agent))
     (wicked/w3m-set-user-agent agent) ;; (7)
     (w3m-reload-this-page)))

 (defadvice w3m-header-arguments (around wicked activate) ;; (8)
   "Check `wicked/w3m-fake-user-agent-sites' for fake user agent definitions."
   (let ((w3m-user-agent w3m-user-agent)
         (w3m-add-user-agent w3m-add-user-agent)
         (sites wicked/w3m-fake-user-agent-sites))
     (while sites
       (if (string-match (caar sites) (ad-get-arg 1))
         (progn
           (wicked/w3m-set-user-agent (cdar sites))
           (setq sites nil))
       (setq sites (cdr sites))))
     ad-do-it))

wicked/w3m-fake-user-agents sets up a number of common user agents(1) using examples from http://www.useragentstring.com. If you frequently use other user agents, add them to this associative list. wicked/w3m-fake-user-agent-sites sets up some rules for URLs so that you can work around specific websites(2). The first matching rule will be used.

wicked/w3m-set-user-agent can be called from a w3m browser session to set the user agent for all new pages visited. By default, it uses the w3m user agent(3). It will also use the w3m user agent if the agent is blank(4). If the user agent is one of the frequently-used agents defined in wicked/w3m-fake-user-agents, then the corresponding user agent string will be used(5). If not, the string will be used as-is(6). If the agent is nil, the user agent string will be disabled.(7)

You can check a single page using a different user agent by using M-x wicked/w3m-reload-this-page-with-user-agent. It temporarily sets the user agent and then reloads the current page.(7)

The last segment of code modifies the behavior of w3m-header-arguments(8), matching wicked/w3m-fake-user-agents against the URL. This temporarily sets the user agent for matching sites.