hgweb: insert followlines buttons before any children, including text nodes

This way the buttons come before any other content, including text nodes.
Because highlight extension replaces every line of text with some <span>
elements that have CSS classes for highlighting, the placement of followlines
buttons used to depend on if that extension was enabled or not. Let's make the
placement more consistent, it'll help the next patch in this series.

mercurial/templates/static/followlines.js

@@ -1,286 +1,286 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;
     }
 
     // Tag of children of "sourcelines" element on which to add "line
     // selection" style.
     var selectableTag = sourcelines.dataset.selectabletag;
     if (typeof selectableTag === 'undefined') {
         return;
     }
 
     var isHead = parseInt(sourcelines.dataset.ishead || "0");
 
     //* 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;
     }
 
     // retrieve all direct *selectable* children of class="sourcelines"
     // element
     var selectableElements = Array.prototype.filter.call(
         sourcelines.children,
         function(x) { return x.tagName === selectableTag; });
 
     var btnTitleStart = 'start following lines history from here';
     var btnTitleEnd = 'terminate line block selection here';
 
     //** return a <button> element with +/- spans */
     function createButton() {
         var btn = document.createElement('button');
         btn.title = btnTitleStart;
         btn.classList.add('btn-followlines');
         var plusSpan = document.createElement('span');
         plusSpan.classList.add('followlines-plus');
         plusSpan.textContent = '+';
         btn.appendChild(plusSpan);
         var br = document.createElement('br');
         btn.appendChild(br);
         var minusSpan = document.createElement('span');
         minusSpan.classList.add('followlines-minus');
         minusSpan.textContent = '−';
         btn.appendChild(minusSpan);
         return btn;
     }
 
     // extend DOM with CSS class for selection highlight and action buttons
     var followlinesButtons = [];
     for (var i = 0; i < selectableElements.length; i++) {
         selectableElements[i].classList.add('followlines-select');
         var btn = createButton();
         followlinesButtons.push(btn);
         // insert the <button> as child of `selectableElements[i]` unless the
         // latter has itself a child  with a "followlines-btn-parent" class
         // (annotate view)
         var btnSupportElm = selectableElements[i];
         var childSupportElms = btnSupportElm.getElementsByClassName(
             'followlines-btn-parent');
         if ( childSupportElms.length > 0 ) {
             btnSupportElm = childSupportElms[0];
         }
-        var refNode = btnSupportElm.children[0]; // node to insert <button> before
+        var refNode = btnSupportElm.childNodes[0]; // node to insert <button> before
         btnSupportElm.insertBefore(btn, refNode);
     }
 
     // ** re-initialize followlines buttons */
     function resetButtons() {
         for (var i = 0; i < followlinesButtons.length; i++) {
             var btn = followlinesButtons[i];
             btn.title = btnTitleStart;
             btn.classList.remove('btn-followlines-end');
             btn.classList.remove('btn-followlines-hidden');
         }
     }
 
     var lineSelectedCSSClass = 'followlines-selected';
 
     //** add CSS class on selectable elements in `from`-`to` line range */
     function addSelectedCSSClass(from, to) {
         for (var i = from; i <= to; i++) {
             selectableElements[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 element of type "selectableTag" parent of `element` */
     function selectableParent(element) {
         var parent = element.parentElement;
         if (parent === null) {
             return null;
         }
         if (element.tagName === selectableTag && parent.isSameNode(sourcelines)) {
             return element;
         }
         return selectableParent(parent);
     }
 
     // ** update buttons title and style upon first click */
     function updateButtons(selectable) {
         for (var i = 0; i < followlinesButtons.length; i++) {
             var btn = followlinesButtons[i];
             btn.title = btnTitleEnd;
             btn.classList.add('btn-followlines-end');
         }
         // on clicked button, change title to "cancel"
         var clicked = selectable.getElementsByClassName('btn-followlines')[0];
         clicked.title = 'cancel';
         clicked.classList.remove('btn-followlines-end');
     }
 
     //** add `listener` on "click" event for all `followlinesButtons` */
     function buttonsAddEventListener(listener) {
         for (var i = 0; i < followlinesButtons.length; i++) {
             followlinesButtons[i].addEventListener('click', listener);
         }
     }
 
     //** remove `listener` on "click" event for all `followlinesButtons` */
     function buttonsRemoveEventListener(listener) {
         for (var i = 0; i < followlinesButtons.length; i++) {
             followlinesButtons[i].removeEventListener('click', listener);
         }
     }
 
     //** event handler for "click" on the first line of a block */
     function lineSelectStart(e) {
         var startElement = selectableParent(e.target.parentElement);
         if (startElement === null) {
             // not a "selectable" element (maybe <a>): abort, keeping event
             // listener registered for other click with a "selectable" target
             return;
         }
 
         // update button tooltip text and CSS
         updateButtons(startElement);
 
         var startId = parseInt(startElement.id.slice(1));
         startElement.classList.add(lineSelectedCSSClass); // CSS
 
         // remove this event listener
         buttonsRemoveEventListener(lineSelectStart);
 
         //** event handler for "click" on the last line of the block */
         function lineSelectEnd(e) {
             var endElement = selectableParent(e.target.parentElement);
             if (endElement === null) {
                 // not a <span> (maybe <a>): abort, keeping event listener
                 // registered for other click with <span> target
                 return;
             }
 
             // remove this event listener
             buttonsRemoveEventListener(lineSelectEnd);
 
             // reset button tooltip text
             resetButtons();
 
             // 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)
                 removeSelectedCSSClass();
                 buttonsAddEventListener(lineSelectStart);
                 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, isHead);
             var div = divAndButton[0],
                 button = divAndButton[1];
             inviteElement.appendChild(div);
             // set position close to cursor (top-right)
             positionTopRight(div, e);
             // hide all buttons
             for (var i = 0; i < followlinesButtons.length; i++) {
                 followlinesButtons[i].classList.add('btn-followlines-hidden');
             }
 
             //** event handler for cancelling selection */
             function cancel() {
                 // remove invite box
                 div.parentNode.removeChild(div);
                 // restore initial event listeners
                 buttonsAddEventListener(lineSelectStart);
                 buttonsRemoveEventListener(cancel);
                 for (var i = 0; i < followlinesButtons.length; i++) {
                     followlinesButtons[i].classList.remove('btn-followlines-hidden');
                 }
                 // remove styles on selected lines
                 removeSelectedCSSClass();
                 resetButtons();
             }
 
             // bind cancel event to click on <button>
             button.addEventListener('click', cancel);
             // as well as on an click on any source line
             buttonsAddEventListener(cancel);
         }
 
         buttonsAddEventListener(lineSelectEnd);
 
     }
 
     buttonsAddEventListener(lineSelectStart);
 
     //** return a <div id="followlines"> and inner cancel <button> elements */
     function followlinesBox(targetUri, fromline, toline, isHead) {
         // <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');
         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;
         aAsc.setAttribute('href', url);
         aAsc.textContent = 'older';
         aDiv.appendChild(aAsc);
 
         if (!isHead) {
             var sep = document.createTextNode(' / ');
             aDiv.appendChild(sep);
             //     link to "descending" followlines
             var aDesc = document.createElement('a');
             aDesc.setAttribute('href', url + '&descend=');
             aDesc.textContent = 'newer';
             aDiv.appendChild(aDesc);
         }
 
         div.appendChild(aDiv);
 
         return [div, button];
     }
 
 }, false);