Skip to content

07) Floating UI

Date: 2023-09-22




Codex needs a comprehensive solution for handling the positioning and behavior of various floating elements – drop-down menus, tooltips, dialogs, etc. We need to ensure that these elements demonstrate the correct behavior in a variety of circumstances:

  • inside multiple scrolling parents,
  • inside dialogs,
  • in right-to-left (RTL) contexts,
  • etc.

See Phabricator task T346099 for the current status of this work.

Considered actions

We explored a variety of different solutions to this problem in T345116. We considered the following different options:

  • Re-use/adapt OOUI's ClippableElement and FloatableElement mixins
  • Develop our own custom solution relying on more modern browser APIs (resize and intersection observer, passive scroll listeners, etc.)
  • Leverage an existing 3rd-party library (out of these, Floating UI looked most promising)

We concluded that re-using the OOUI solutions verbatim was not really feasible for Codex – OOUI is heavily reliant on jQuery (which Codex does not use) and the browser landscape has also changed considerably in the last few years (we now can safely rely on new APIs like intersection and resize observers, etc).

We also realized that re-writing a complete solution entirely from scratch would take a considerable amount of time and effort, significantly delaying the production-readiness of Codex.


After some investigation (see T345116), we believe that the best path forward is to leverage the Floating UI library and avoid re-inventing the wheel ourselves.

Floating UI is the successor to Popper.js, which was incorporated into Bootstrap to solve similar problems. This new library is similarly intended for this kind of low-level, embedded-inside-another-UI-library usage, while making use of modern browser capabilities and working well with frameworks like React and Vue. Additionally, Floating UI's API includes a concept of "middleware" (chainable plugins) which we can rely on if we need to customize the library's behavior (for example, to provide specific RTL support).

Finally, Floating UI already includes a Vue.js composable, useFloating, which greatly simplified adoption efforts.


Adding a new runtime dependency to Codex is not something we do lightly.

DST engineers conducted a preliminary security review of Floating UI (see here for details). We will follow up with a more formal discussion with the Wikimedia Foundation's security team to ensure that Codex follows appropriate security practices for a library of its type.

This task describes the initial work that has been done to incorporate Floating UI into Codex.

Regarding RTL behavior, our initial investigations indicate that this approach is compatible with our current strategy for supporting bi-directionality.

In the future, we may add additional behavior to our Menu components (flipping/clipping based on available space, etc.). Fortunately the library's modular concept of "middleware" makes it easy to introduce and fine-tune this kind of added behavior.