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
  10 in_module(null);
  11
  12 define_variable("headings_xpath",
  13     "//h1 | //h2 | //h3 | //h4 | //h5 | //h6 | //xhtml:h1 | "+
  14     "//xhtml:h2 | //xhtml:h3 | //xhtml:h4 | //xhtml:h5 | //xhtml:h6",
  15     "The xpath expression used by next-heading and previous-heading to find "+
  16     "headings.  Users will rarely need to change the value of this, but it "+
  17     "exists especially for page-modes to override with a site-specific "+
  18     "xpath expression.");
  19
  20
  21 define_variable("scroll_to_heading_wrap", true,
  22     "If true, will wrap to the topmost heading when the viewport is at the "+
  23     "bottom of the document and the user tries to access the next heading. "+
  24     "Does the equivalent thing for \"previous heading\" as well.");
  25
  26
  27 define_browser_object_class("next-heading", null,
  28     function (I) {
  29         let xpr = I.buffer.document.evaluate(
  30             I.local.headings_xpath, I.buffer.document, xpath_lookup_namespace,
  31             Ci.nsIDOMXPathResult.ORDERED_NODE_ITERATOR_TYPE, null),
  32         heading, found = null, foundtop = null,
  33         first = null, firsttop = null;
  34         while ((heading = xpr.iterateNext())) {
  35             let rect = heading.getBoundingClientRect();
  36             if (rect.bottom - rect.top < 2)
  37                 continue;
  38             if (! first || rect.top < firsttop) {
  39                 first = heading;
  40                 firsttop = rect.top;
  41             }
  42             if (rect.top > 2 && (! found || rect.top < foundtop)) {
  43                 found = heading;
  44                 foundtop = rect.top;
  45             }
  46         }
  47         // scrollY can exceed scrollMaxY
  48         let eod = I.buffer.scrollY - I.buffer.scrollMaxY >= 0;
  49         if ((!found || eod) && scroll_to_heading_wrap)
  50             found = first;
  51         yield co_return(found);
  52     });
  53
  54
  55 define_browser_object_class("previous-heading", null,
  56     function (I) {
  57         let xpr = I.buffer.document.evaluate(
  58             I.local.headings_xpath, I.buffer.document,  xpath_lookup_namespace,
  59             Ci.nsIDOMXPathResult.ORDERED_NODE_ITERATOR_TYPE, null),
  60         heading, found = null, foundtop = null,
  61         last = null, lasttop = null;
  62         while ((heading = xpr.iterateNext())) {
  63             let rect = heading.getBoundingClientRect();
  64             if (rect.bottom - rect.top < 2)
  65                 continue;
  66             if (rect.top < -1 && (! found || rect.top > foundtop)) {
  67                 found = heading;
  68                 foundtop = rect.top;
  69             }
  70             if (! last || rect.top > lasttop) {
  71                 last = heading;
  72                 lasttop = rect.top;
  73             }
  74         }
  75         if (! found && scroll_to_heading_wrap)
  76             found = last;
  77         yield co_return(found);
  78     });
  79
  80
  81 function scroll (I) {
  82     var o = yield read_browser_object(I);
  83     // no scrolling and no error if we failed to get an object.
  84     if (! o)
  85         yield co_return();
  86     if (o instanceof load_spec)
  87         o = load_spec_element(o);
  88     if (o instanceof Ci.nsIDOMWindow) {
  89         // scroll to #ref or top
  90         var ref = o.document.documentURIObject.ref;
  91         if (ref) {
  92             var xpr = I.buffer.document.evaluate(
  93                 "//*[@id='"+ref+"']|//*[@name='"+ref+"']",
  94                 o.document, xpath_lookup_namespace,
  95                 Ci.nsIDOMXPathResult.FIRST_ORDERED_NODE_TYPE, null);
  96             var node = xpr.singleNodeValue;
  97             if (node) {
  98                 var rect = node.getBoundingClientRect();
  99                 o.scrollTo(0, o.scrollY + rect.top);
 100             } else
 101                 o.scrollTo(0, 0);
 102         } else
 103             o.scrollTo(0, 0);
 104     } else if (o instanceof Ci.nsIDOMNode) {
 105         o.scrollIntoView();
 106         I.window.minibuffer.message(o.textContent);
 107     } else {
 108         throw interactive_error("Cannot scroll to given item");
 109     }
 110 }
 111
 112
 113 interactive("scroll",
 114     "Generalized scroll command.\nThe amount of scrolling is determined by "+
 115     "the object passed to the command as a browser-object.  If the object "+
 116     "is a DOM node, that node will be scrolled to the top of the viewport "+
 117     "if possible.",
 118     scroll,
 119     $browser_object = null);
 120
 121 provide("scroll");