Thursday, February 23, 2006

Emacspeak: Connecting Lynx And W3

Emacs/W3 is still the best Web page rendering option inside Emacspeak given the ability to apply XSL transforms, as well as obtaining aural styling via ACSS. However W3's url handling layer often breaks when faced with multiple redirects, especially when some of these happen through the Host: HTTP header. Additionally, HTTPS authentication sometimes fails mysteriously in the presence of redirects.

In many of these cases, lynx happily fetches the pages correctly; however you're then stuck using a fairly weak auditory interface in that Emacspeak degrades to being aterminal level screenreader.

An effective solution to this problem is to use lynx within an Emacs terminal, and after finding the content that is worth reading, handing off that content to Emacs/W3. The next few paragraphs show how.

The lynx-site.cfg File

This is where you add site-specific configurations. Here are the lines I have in my lynx-site.cfg to integrate lynx and Emacs. Before you use any of this, make sure you have executed M-x server-start in your running Emacs, and make sure that all is well by experimenting with emacsclient to ensure that external programs can hand-off editting tasks to the currently running Emacs.

#site defaults
#for bookshare:
DOWNLOADER:BKS Unpack:bks.pl  %s %s:TRUE 
PRINTER:Edit:emacsclient %s:TRUE
KEYMAP:???:EDITTEXTAREA	# use external editor to edit a form textarea
PRETTYSRC:TRUE
SOURCE_CACHE:MEMORY
SAVE_SPACE:~/.wget/
BOLD_HEADERS:TRUE
PRINTER:W3:emacsclient -e '(w3-open-local "%s")':TRUE

Below, I'll describe what each of the above lines do:

  • DOWNLOADER:BKS Unpack:bks.pl %s %s:TRUE
    The above line creates an additional item in the download menu that invokes the BookShare unpacker. Script bks-unpack.pl invokes the BookShare unpack tool with the appropriate options.
  • PRINTER:Edit:emacsclient %s:TRUE
    This creates an Edit item in the print menu. Invoking this menu item causes the current page to be handed off to Emacs for editting. If you want to edit the source, first switch to source view by hitting \ before invoking print.
  • KEYMAP:???:EDITTEXTAREA # use external editor to edit a form textarea
    This sets lynx up so that when editting a multiline textarea, you can hand off the editting job to Emacs. This is particularly useful for editting Wiki pages. Replace the ?? with the desired key sequence.
  • PRETTYSRC:TRUE
    SOURCE_CACHE:MEMORY
    The above two settings make the edit source functionality more pleasant to use.
  • PRINTER:W3:emacsclient -e '(w3-open-local "%s")':TRUE
    The above creates a W3 menu item in the print menu. Invoking this causes Emacs/W3 to display the current page --- again switch to source view before invoking this so that Emacs/W3 gets handed the HTML markup.

Script bks-unpack.pl

#!/usr/bin/perl -w
#$Id: bks.pl,v 1.1 2003/07/04 15:41:55 tvraman Exp tvraman $
#Description: Bookshare downloader for Lynx
use strict;
my $location="$ENV{HOME}/books/book-share";
my $password = 'xxxxxxx';
my $grabbed = shift;
my $target = shift;
my $dir =qx(basename $target .bks);
chomp $dir;
my $where = "$location/$dir";
qx(mkdir -p $where);
qx(mv $grabbed  $where/$target);
chdir $where;
qx(echo $password | bks-unpack -q $target 1>&- 2>&- &);
at