def gen_tasks(self):
        """Build HTML fragments from metadata and text."""
        self.site.scan_posts()
        kw = {
            "translations": self.site.config["TRANSLATIONS"],
            "timeline": self.site.timeline,
            "default_lang": self.site.config["DEFAULT_LANG"],
            "show_untranslated_posts": self.site.config['SHOW_UNTRANSLATED_POSTS'],
            "demote_headers": self.site.config['DEMOTE_HEADERS'],
        }
        self.tl_changed = False

        yield self.group_task()

        def tl_ch():
            self.tl_changed = True

        yield {
            'basename': self.name,
            'name': 'timeline_changes',
            'actions': [tl_ch],
            'uptodate': [utils.config_changed({1: kw['timeline']})],
        }

        for lang in kw["translations"]:
            deps_dict = copy(kw)
            deps_dict.pop('timeline')
            for post in kw['timeline']:
                if not post.is_translation_available(lang) and not self.site.config['SHOW_UNTRANSLATED_POSTS']:
                    continue
                # Extra config dependencies picked from config
                for p in post.fragment_deps(lang):
                    if p.startswith('####MAGIC####CONFIG:'):
                        k = p.split('####MAGIC####CONFIG:', 1)[-1]
                        deps_dict[k] = self.site.config.get(k)
                dest = post.translated_base_path(lang)
                file_dep = [p for p in post.fragment_deps(lang) if not p.startswith("####MAGIC####")]
                extra_targets = post.compiler.get_extra_targets(post, lang, dest)
                task = {
                    'basename': self.name,
                    'name': dest,
                    'file_dep': file_dep,
                    'targets': [dest] + extra_targets,
                    'actions': [(post.compile, (lang, )),
                                (update_deps, (post, lang, )),
                                ],
                    'clean': True,
                    'uptodate': [
                        utils.config_changed(deps_dict, 'nikola.plugins.task.posts'),
                        lambda p=post, l=lang: self.dependence_on_timeline(p, l)
                    ] + post.fragment_deps_uptodate(lang),
                    'task_dep': ['render_posts:timeline_changes']
                }

                # Apply filters specified in the metadata
                ff = [x.strip() for x in post.meta('filters', lang).split(',')]
                flist = []
                for i, f in enumerate(ff):
                    if not f:
                        continue
                    _f = self.site.filters.get(f)
                    if _f is not None:  # A registered filter
                        flist.append(_f)
                    else:
                        flist.append(f)
                yield utils.apply_filters(task, {os.path.splitext(dest)[-1]: flist})