Scroll to and select first merge conflict in editor

When a user is thrown back to the editor because there are conflicts to
handle, the editor is now scrolled to the first conflict automatically.

Only tested in Chrome so far.

inc/actions.php

@@ -331,6 +331,7 @@ function act_save($act){
     global $SUM;
     global $lang;
     global $INFO;
+    global $JSINFO;
 
     //spam check
     if(checkwordblock()) {
@@ -344,6 +345,7 @@ function act_save($act){
     //deny saving when merge markers are present
     if(preg_match('/^(✎|✏|✐)——————/m',$mine)){
             msg('Please resolve the conflicts',-1); //FIXME localize
+            $JSINFO['selectConflict'] = 'wiki__text';
             return 'edit';
     }
 
@@ -374,6 +376,7 @@ function act_save($act){
             $TEXT = $final;
 
             msg('Please resolve the conflicts',-1); //FIXME we'll need more explantion than that
+            $JSINFO['selectConflict'] = 'wiki__text';
             return 'edit';
         }
         // no merge conflicts

lib/exe/js.php

@@ -117,6 +117,7 @@ function js_out(){
     }
     js_runonstart('scrollToMarker()');
     js_runonstart('focusMarker()');
+    js_runonstart('initConflictSelect()');
     // init hotkeys - must have been done after init of toolbar
 # disabled for FS#1958    js_runonstart('initializeHotkeys()');
 

lib/scripts/edit.js

@@ -349,3 +349,50 @@ function summaryCheck(){
     }
 }
 
+/**
+ * selects and scrolls to the first conflict marker
+ *
+ * This runs when the global JSINFO array contains a member 'selectConflict'
+ * containing the ID of a textarea to work on
+ *
+ * @author Andreas Gohr <andi@splitbrain.org>
+ */
+function initConflictSelect(){
+    if(!JSINFO.selectConflict) return;
+    var field     = $(JSINFO.selectConflict);
+    if(!field) return;
+
+    // find the conflict markers
+    var start = field.value.indexOf('✎—————');
+    if(start < 0) return;
+    var end   = field.value.indexOf('✐—————');
+    if(end < 0) {
+        end = start;
+    } else {
+        end += 48;
+    }
+
+    // prepare selection
+    var selection = getSelection(field);
+    selection.start  = start;
+    selection.end    = end;
+
+
+    // find out how far to scroll to show selection
+    // we need to create a dummy pre tag to let the browser calculate the
+    // scroll height for us
+    // see http://wiki.sheep.art.pl/Textarea%20Scrolling
+    var scrollPre = document.createElement('pre');
+    field.parentNode.appendChild(scrollPre);
+    scrollPre.style = field.style;
+    scrollPre.style.padding = 0;
+    scrollPre.style.overflow = 'scroll';
+    scrollPre.textContent = field.value.substr(0,start);
+    selection.scroll = scrollPre.scrollHeight;
+    scrollPre.parentNode.removeChild(scrollPre);
+
+    // finally set the selection
+    setSelection(selection);
+}
+
+