modules/scroll.js

   1 /**
   2  * (C) Copyright 2009 Shawn Betts
   3  * (C) Copyright 2009,2011 John J. Foerch <jjfoerch@earthlink.net>
   4  *
   5  * Use, modification, and distribution are subject to the terms specified in the
   6  * COPYING file.
   7 **/
   8
   9 define_variable("headings_xpath",
  10     "//h1 | //h2 | //h3 | //h4 | //h5 | //h6 | //xhtml:h1 | "+
  11     "//xhtml:h2 | //xhtml:h3 | //xhtml:h4 | //xhtml:h5 | //xhtml:h6",
  12     "The xpath expression used by next-heading and previous-heading to find "+
  13     "headings.  Users will rarely need to change the value of this, but it "+
  14     "exists especially for page-modes to override with a site-specific "+
  15     "xpath expression.");
  16
  17
  18 define_variable("scroll_to_heading_wrap", true,
  19     "If true, will wrap to the topmost heading when the viewport is at the "+
  20     "bottom of the document and the user tries to access the next heading. "+
  21     "Does the equivalent thing for \"previous heading\" as well.");
  22
  23
  24 define_browser_object_class("next-heading", null,
  25     function (I) {
  26         let xpr = I.buffer.document.evaluate(
  27             I.local.headings_xpath, I.buffer.document, xpath_lookup_namespace,
  28             Ci.nsIDOMXPathResult.ORDERED_NODE_ITERATOR_TYPE, null),
  29         heading, found = null, foundtop = null,
  30         first = null, firsttop = null;
  31         while ((heading = xpr.iterateNext())) {
  32             let rect = heading.getBoundingClientRect();
  33             if (rect.bottom - rect.top < 2)
  34                 continue;
  35             if (! first || rect.top < firsttop) {
  36                 first = heading;
  37                 firsttop = rect.top;
  38             }
  39             if (rect.top > 2 && (! found || rect.top < foundtop)) {
  40                 found = heading;
  41                 foundtop = rect.top;
  42             }
  43         }
  44         // scrollY can exceed scrollMaxY
  45         let eod = I.buffer.scrollY - I.buffer.scrollMaxY >= 0;
  46         if ((!found || eod) && scroll_to_heading_wrap)
  47             found = first;
  48         yield co_return(found);
  49     });
  50
  51
  52 define_browser_object_class("previous-heading", null,
  53     function (I) {
  54         let xpr = I.buffer.document.evaluate(
  55             I.local.headings_xpath, I.buffer.document,  xpath_lookup_namespace,
  56             Ci.nsIDOMXPathResult.ORDERED_NODE_ITERATOR_TYPE, null),
  57         heading, found = null, foundtop = null,
  58         last = null, lasttop = null;
  59         while ((heading = xpr.iterateNext())) {
  60             let rect = heading.getBoundingClientRect();
  61             if (rect.bottom - rect.top < 2)
  62                 continue;
  63             if (rect.top < -1 && (! found || rect.top > foundtop)) {
  64                 found = heading;
  65                 foundtop = rect.top;
  66             }
  67             if (! last || rect.top > lasttop) {
  68                 last = heading;
  69                 lasttop = rect.top;
  70             }
  71         }
  72         if (! found && scroll_to_heading_wrap)
  73             found = last;
  74         yield co_return(found);
  75     });
  76
  77
  78 function scroll (I) {
  79     var o = yield read_browser_object(I);
  80     // no scrolling and no error if we failed to get an object.
  81     if (! o)
  82         yield co_return();
  83     if (o instanceof load_spec)
  84         o = load_spec_element(o);
  85     if (o instanceof Ci.nsIDOMWindow) {
  86         // scroll to #ref or top
  87         var ref = o.document.documentURIObject.ref;
  88         if (ref) {
  89             var xpr = I.buffer.document.evaluate(
  90                 "//*[@id='"+ref+"']|//*[@name='"+ref+"']",
  91                 o.document, xpath_lookup_namespace,
  92                 Ci.nsIDOMXPathResult.FIRST_ORDERED_NODE_TYPE, null);
  93             var node = xpr.singleNodeValue;
  94             if (node) {
  95                 var rect = node.getBoundingClientRect();
  96                 o.scrollTo(0, o.scrollY + rect.top);
  97             } else
  98                 o.scrollTo(0, 0);
  99         } else
 100             o.scrollTo(0, 0);
 101     } else if (o instanceof Ci.nsIDOMNode) {
 102         o.scrollIntoView();
 103         I.window.minibuffer.message(o.textContent);
 104     } else {
 105         throw interactive_error("Cannot scroll to given item");
 106     }
 107 }
 108
 109
 110 interactive("scroll",
 111     "Generalized scroll command.\nThe amount of scrolling is determined by "+
 112     "the object passed to the command as a browser-object.  If the object "+
 113     "is a DOM node, that node will be scrolled to the top of the viewport "+
 114     "if possible.",
 115     scroll,
 116     $browser_object = null);
 117
 118 provide("scroll");