Vimperator + Reader View

Jun 9, 2015

Firefox 38.0.5 introduced Reader View which strips out everything except the main content of a page for easier reading. I use vimperator and wanted to add a key mapping to quickly go into reader view. To save others the trouble of figuring it out, here’s how:

Basically all the little reader button does is prepend "about:reader?url=" to the current URL so all we need to do is write a command that does just that. Turns out it’s easier said than done. I hunted through the vimperator documentation, experimenting with copying the URL with y (but there’s no way to paste), using <url> in the command specification (doesn’t work), and creating macros (inelegant and the @ key is too far away) to no avail.

Finally I found the :execute command and content.location.href which isn’t documented at all but expands to the current URL. It can then be concatenated into a command with + in the argument of :execute.

Without further ado, execute the following in vimperator:

:command reader :execute "open about:reader?url=" + content.location.href
:map gr :reader<CR>
:mkvimperatorrc

Or equivalently, add the following to your .vimperatorrc:

command reader :execute "open about:reader?url=" + content.location.href
map gr :reader<Return>

This can cause strange behavior if you call it on a page that’s already in reader mode. It will get ‘stuck’ and H to go back doesn’t work but 2H will.

There is a way to prevent this using javascript’s conditional operator condition ? expr1 : expr2. This evaluates to expr1 if the condition is true and expr2 if the condition is false. The condition will be whether we’re already in reader view (whether the URL starts with "about:reader"), if we are, go back to normal mode (remove the "about:reader"?url=", and if not, go to reader mode same as before.
Thus:

:command! reader :execute ((content.location.href.indexOf("about:reader?url=") !== -1) ? ("open " + content.href.substring(17)) : ("open about:reader?url=" + content.location.href))
:mkvimperatorrc!

or in .vimperatorrc:

command reader :execute ((content.location.href.indexOf("about:reader?url=") !== -1) ? ("open " + content.location.href.substring(17)) : ("open about:reader?url=" + content.location.href))