D12: htmx4 compatibility [#3620792]

Problem/Motivation

htmx 4 is committed and will be in Drupal 12: https://git.drupalcode.org/project/drupal/commit/2aa5aede43f

There may be some impacts for Display Builder.

Potential compatibility breaks:

Attribute inheritance is now explicit: I don't think we are using much but let's be careful: https://four.htmx.org/announcements/2026-08-28-htmx-4.0.0-is-released#at...
Some events names have changed https://four.htmx.org/announcements/2026-08-28-htmx-4.0.0-is-released#ev...

Opportunities to simplify/consolidate our codebase:

2 new swaps which are preserving the DOM state, may be useful to preserve form states or sortablejs stuff https://four.htmx.org/announcements/2026-08-28-htmx-4.0.0-is-released#mo...
hx-partial webcomponents to handle oob-swaps (maybe Drupal Core will implements a dedicated render element) https://four.htmx.org/announcements/2026-08-28-htmx-4.0.0-is-released#hx...

Proposed resolution

How can we manage this?

The real challenge will be to be compatible with both htmx2 on Drupal 11.x and htmx4 on Drupal 12.x.

Comment	File	Size	Author
#3	d12p-w12-builder-fixed-01.png	253.42 KB	rajab natshah
#3	d12p-w12-builder-01.png	120.01 KB	rajab natshah

Issue fork display_builder-3620792

Show commands

Start within a Git clone of the project using the version control instructions.

Add & fetch this issue fork’s repository

Or, if you do not have SSH keys set up on git.drupalcode.org:

Add & fetch this issue fork’s repository

3620792-info-and-views changes, plain diff MR !460
Check out this branch for the first time

Check out existing branch, if you already have it locally
3620792-d12-htmx4-compatibility compare
Check out this branch for the first time

Check out existing branch, if you already have it locally

About issue forks

Comments

Comment #1

4 September 2026 at 06:14

pdureau created an issue. See original summary.

Comment #2

pdureau commented 4 September 2026 at 11:00

According to @fathershawn, we can use this to be be compatible with both:

Use \Drupal\Component\Utility\DeprecationHelper to call the different methods on Htmx in PHP.
Load the htmx compatibility extension to help with the event names. I’m in the process of putting together a 3.x of the htmx contrib module with a bunch of extensions.

I guess compatibility here means: we keep using htmx2 API in Display Builder as long as we support Drupal 11.x, but those tricks make us compatible with Drupal 12.

Also, for "Attribute inheritance", i guess being explicit (which is mandatory in htmx4) is backward compatible with htmx2, because same mechanism and keywords.

Let's check all this.

Comment #3

rajab natshah

he/him

commented 4 October 2026 at 13:07

Status	File	Size
new	d12p-w12-builder-01.png	120.01 KB
new	d12p-w12-builder-fixed-01.png	253.42 KB

On Drupal 12.0.0-beta1 (PHP 8.5) with ^12 in the info files, Display Builder 1.0.0-beta8 installs and pages render, but builder pages return 500: HtmxEvents::onClickSavePreset() calls Htmx::prompt(), removed with htmx 4. With that call guarded, the canvas shows but the toolbar stays empty. display_builder_views also fails, because ViewDisplay::collectInstances() reads the now protected View::$display.

Screenshot