hgweb: add a link to followlines in descending direction

We change the content of the followlines popup to display two links inviting
to follow the history of selected lines in ascending (as before) and
descending directions. The popup now renders as:

  follow history of lines <fromline>:<toline>:
  <a href=...>ascending</a> / <a href=...>descending</a>

mercurial/templates/static/followlines.js

@@ -1,219 +1,229 b''
 // followlines.js - JavaScript utilities for followlines UI
 //
 // Copyright 2017 Logilab SA <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //** Install event listeners for line block selection and followlines action */
 document.addEventListener('DOMContentLoaded', function() {
     var sourcelines = document.getElementsByClassName('sourcelines')[0];
     if (typeof sourcelines === 'undefined') {
         return;
     }
     // URL to complement with "linerange" query parameter
     var targetUri = sourcelines.dataset.logurl;
     if (typeof targetUri === 'undefined') {
         return;
     }
 
     // tooltip to invite on lines selection
     var tooltip = document.createElement('div');
     tooltip.id = 'followlines-tooltip';
     tooltip.classList.add('hidden');
     var initTooltipText = 'click to start following lines history from here';
     tooltip.textContent = initTooltipText;
     sourcelines.appendChild(tooltip);
 
     //* position "element" on top-right of cursor */
     function positionTopRight(element, event) {
         var x = (event.clientX + 10) + 'px',
             y = (event.clientY - 20) + 'px';
         element.style.top = y;
         element.style.left = x;
     }
 
     var tooltipTimeoutID;
     //* move the "tooltip" with cursor (top-right) and show it after 1s */
     function moveAndShowTooltip(e) {
         if (typeof tooltipTimeoutID !== 'undefined') {
             // avoid accumulation of timeout callbacks (blinking)
             window.clearTimeout(tooltipTimeoutID);
         }
         tooltip.classList.add('hidden');
         positionTopRight(tooltip, e);
         tooltipTimeoutID = window.setTimeout(function() {
             tooltip.classList.remove('hidden');
         }, 1000);
     }
 
     // on mousemove, show tooltip close to cursor position
     sourcelines.addEventListener('mousemove', moveAndShowTooltip);
 
     // retrieve all direct <span> children of <pre class="sourcelines">
     var spans = Array.prototype.filter.call(
         sourcelines.children,
         function(x) { return x.tagName === 'SPAN' });
 
     // add a "followlines-select" class to change cursor type in CSS
     for (var i = 0; i < spans.length; i++) {
         spans[i].classList.add('followlines-select');
     }
 
     var lineSelectedCSSClass = 'followlines-selected';
 
     //** add CSS class on <span> element in `from`-`to` line range */
     function addSelectedCSSClass(from, to) {
         for (var i = from; i <= to; i++) {
             spans[i].classList.add(lineSelectedCSSClass);
         }
     }
 
     //** remove CSS class from previously selected lines */
     function removeSelectedCSSClass() {
         var elements = sourcelines.getElementsByClassName(
             lineSelectedCSSClass);
         while (elements.length) {
             elements[0].classList.remove(lineSelectedCSSClass);
         }
     }
 
     // ** return the <span> element parent of `element` */
     function findParentSpan(element) {
         var parent = element.parentElement;
         if (parent === null) {
             return null;
         }
         if (element.tagName == 'SPAN' && parent.isSameNode(sourcelines)) {
             return element;
         }
         return findParentSpan(parent);
     }
 
     //** event handler for "click" on the first line of a block */
     function lineSelectStart(e) {
         var startElement = findParentSpan(e.target);
         if (startElement === null) {
             // not a <span> (maybe <a>): abort, keeping event listener
             // registered for other click with <span> target
             return;
         }
 
         // update tooltip text
         tooltip.textContent = 'click again to terminate line block selection here';
 
         var startId = parseInt(startElement.id.slice(1));
         startElement.classList.add(lineSelectedCSSClass); // CSS
 
         // remove this event listener
         sourcelines.removeEventListener('click', lineSelectStart);
 
         //** event handler for "click" on the last line of the block */
         function lineSelectEnd(e) {
             var endElement = findParentSpan(e.target);
             if (endElement === null) {
                 // not a <span> (maybe <a>): abort, keeping event listener
                 // registered for other click with <span> target
                 return;
             }
 
             // remove this event listener
             sourcelines.removeEventListener('click', lineSelectEnd);
 
             // hide tooltip and disable motion tracking
             tooltip.classList.add('hidden');
             sourcelines.removeEventListener('mousemove', moveAndShowTooltip);
             window.clearTimeout(tooltipTimeoutID);
 
             //* restore initial "tooltip" state */
             function restoreTooltip() {
                 tooltip.textContent = initTooltipText;
                 sourcelines.addEventListener('mousemove', moveAndShowTooltip);
             }
 
             // compute line range (startId, endId)
             var endId = parseInt(endElement.id.slice(1));
             if (endId == startId) {
                 // clicked twice the same line, cancel and reset initial state
                 // (CSS, event listener for selection start, tooltip)
                 removeSelectedCSSClass();
                 sourcelines.addEventListener('click', lineSelectStart);
                 restoreTooltip();
                 return;
             }
             var inviteElement = endElement;
             if (endId < startId) {
                 var tmp = endId;
                 endId = startId;
                 startId = tmp;
                 inviteElement = startElement;
             }
 
             addSelectedCSSClass(startId - 1, endId -1);  // CSS
 
             // append the <div id="followlines"> element to last line of the
             // selection block
             var divAndButton = followlinesBox(targetUri, startId, endId);
             var div = divAndButton[0],
                 button = divAndButton[1];
             inviteElement.appendChild(div);
             // set position close to cursor (top-right)
             positionTopRight(div, e);
 
             //** event handler for cancelling selection */
             function cancel() {
                 // remove invite box
                 div.parentNode.removeChild(div);
                 // restore initial event listeners
                 sourcelines.addEventListener('click', lineSelectStart);
                 sourcelines.removeEventListener('click', cancel);
                 // remove styles on selected lines
                 removeSelectedCSSClass();
                 // restore tooltip element
                 restoreTooltip();
             }
 
             // bind cancel event to click on <button>
             button.addEventListener('click', cancel);
             // as well as on an click on any source line
             sourcelines.addEventListener('click', cancel);
         }
 
         sourcelines.addEventListener('click', lineSelectEnd);
 
     }
 
     sourcelines.addEventListener('click', lineSelectStart);
 
     //** return a <div id="followlines"> and inner cancel <button> elements */
     function followlinesBox(targetUri, fromline, toline) {
         // <div id="followlines">
         var div = document.createElement('div');
         div.id = 'followlines';
 
         //   <div class="followlines-cancel">
         var buttonDiv = document.createElement('div');
         buttonDiv.classList.add('followlines-cancel');
 
         //     <button>x</button>
         var button = document.createElement('button');
         button.textContent = 'x';
         buttonDiv.appendChild(button);
         div.appendChild(buttonDiv);
 
         //   <div class="followlines-link">
         var aDiv = document.createElement('div');
         aDiv.classList.add('followlines-link');
-
-        //     <a href="/log/<rev>/<file>?patch=&linerange=...">
-        var a = document.createElement('a');
+        aDiv.textContent = 'follow history of lines ' + fromline + ':' + toline + ':';
+        var linesep = document.createElement('br');
+        aDiv.appendChild(linesep);
+        //     link to "ascending" followlines
+        var aAsc = document.createElement('a');
         var url = targetUri + '?patch=&linerange=' + fromline + ':' + toline;
-        a.setAttribute('href', url);
-        a.textContent = 'follow lines ' + fromline + ':' + toline;
-        aDiv.appendChild(a);
+        aAsc.setAttribute('href', url);
+        aAsc.textContent = 'ascending';
+        aDiv.appendChild(aAsc);
+        var sep = document.createTextNode(' / ');
+        aDiv.appendChild(sep);
+        //     link to "descending" followlines
+        var aDesc = document.createElement('a');
+        aDesc.setAttribute('href', url + '&descend=');
+        aDesc.textContent = 'descending';
+        aDiv.appendChild(aDesc);
+
         div.appendChild(aDiv);
 
         return [div, button];
     }
 
 }, false);