Userscripts.org

// ==UserScript==
// @name           Sinfest prev/next links
// @version        1.1
// @namespace      http://www.lysator.liu.se/~jhs/userscript
// @description    Adds links the previous and next Sinfest strip by clicking the left/right portion of the present strip, and adds access keys P and N (or . and ,) too for concenience (Alt+* on Windows, Command+* on Mac, Shift+Escape followed by * in Opera).
// @include        http://www.sinfest.net/archive_page*
// @include        http://www.sinfest.net/*
// ==/UserScript==

function $x( xpath, root )
{
  var doc = root ? root.evaluate ? root : root.ownerDocument : document, next;
  var got = doc.evaluate( xpath, root||doc, null, 0, null ), result = [];
  while( next = got.iterateNext() )
    result.push( next );
  return result;
}

function link_surrounding_strips()
{
  var img = $x( '//img[contains(@src, "comics")]' )[0];
  var m = document.createElement( 'map' ); m.name = 'prev-next';
  var p = document.createElement( 'area' ); p.shape = 'rect';
  var n = document.createElement( 'area' ); n.shape = 'rect';
  var w = img.width, W = Math.floor( w/2 ), h = img.height, u;
  if( (u = $x( '//a[img[@alt="Previous"]]' )).length )
  {
    u[0].accessKey = ',';
    p.accessKey = 'P';
    p.coords = '0,0,'+ W +','+ h;
    //p.title = 'Previous strip';
    p.href = u[0].href;
    m.appendChild( p );
  }
  if( (u = $x( '//a[img[@alt="Next"]]' )).length )
  {
    u[0].accessKey = '.';
    n.accessKey = 'N';
    n.coords = W +',0,'+ (--w) +','+ h;
    //n.title = 'Next strip';
    n.href = u[0].href;
    m.appendChild( n );
  }
  document.body.appendChild( m );
  img.setAttribute( 'usemap', '#prev-next' );
}

function hook_up_strip()
{
  var i = $x( '//img[contains(@src, "comics")]' );
  if( !i.length ) return;
  if( i[0].width * i[0].height > 1e5 )
    link_surrounding_strips();
  else
    i[0].addEventListener( 'load', link_surrounding_strips, false );
}

hook_up_strip();