Asking for feedback: Tag Reveal Component in Topic Lists - Expand/Collapse tags in topic lists

Dev
15

You use this in a class. It won’t work otherwise.

You want to write 3.6.0.beta1 then, otherwise no one can install it at the moment.

I did check a bit. Indeed, there is no straightforward way to achieve that; however, I found an interesting and simplified method to do it using the API.

  • It uses the topic model to change what visible tags will be output before the template is generated. It means no DOM manipulation and settings agnostic. Depending on the state (revealTags), it will return the original list or a partial one.

  • To create the toggle button, it uses the API to add a tag with the HTML of a button (unfortunately, there is no plugin outlet here). The click event is handled separately. On click, the toggle state is updated (revealTags), and we trigger a re-render of the tags list.

The big advantage of this way is that you don’t have to mess with the HTML and figure out what to show/unhide with CSS, based on the different styles.

chrome_lSKqwYt5Z7

Sharing my test code here:

import { apiInitializer } from "discourse/lib/api";
import { i18n } from "discourse-i18n";
import { computed } from "@ember/object";

export default apiInitializer((api) => {
  const siteSettings = api.container.lookup("service:site-settings");

  const maxVisibleTags = Math.min(
    settings.max_tags_visible,
    siteSettings.max_tags_per_topic
  );

  let topicModels = {};

  api.modifyClass(
    "model:topic",
    (Superclass) =>
      class extends Superclass {
        revealTags = false;

        init() {
          super.init(...arguments);
          topicModels[this.id] = this;
        }

        @computed("tags")
        get visibleListTags() {
          if (this.revealTags) {
            return super.visibleListTags;
          }
          return super.visibleListTags.slice(0, maxVisibleTags);
        }
      }
  );

  api.addTagsHtmlCallback(
    (topic, params) => {
      if (topic.tags.length <= maxVisibleTags) {
        return "";
      }

      const isExpanded = topic.revealTags;
      const label = isExpanded
        ? i18n(themePrefix("js.tag_reveal.hide"))
        : i18n(themePrefix("js.tag_reveal.more_tags"), {
            count: topic.tags.length - maxVisibleTags,
          });

      return `<a class="reveal-tag-action" role="button" aria-expanded="${isExpanded}">${label}</a>`;
    },
    {
      priority: siteSettings.max_tags_per_topic + 1,
    }
  );

  document.addEventListener("click", (event) => {
    const target = event.target;
    if (!target?.matches(".reveal-tag-action")) {
      return;
    }

    event.preventDefault();
    event.stopPropagation();

    const element =
      target.closest("[data-topic-id]") ||
      document.querySelector("h1[data-topic-id]");
    const topicId = element?.dataset.topicId;
    if (!topicId) {
      return;
    }

    const topicModel = topicModels[topicId];
    if (!topicModel) {
      return;
    }

    topicModel.revealTags = !topicModel.revealTags;
    topicModel.notifyPropertyChange("tags");
  });
});

.reveal-tag-action {
  background-color: var(--primary-50);
  border: 1px solid var(--primary-200);
  color: var(--primary-800);
  font-size: small;
  padding-inline: 3px;
}

.discourse-tags__tag-separator:has(+ .reveal-tag-action) {
  visibility: hidden;
}
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