CKEditor no HTML flash

This module fixes a UX issue in core's implementation of the CKEditor5 module. When the user saves
a form using CKEditor5, there is a "flash" of plain HTML when the form is submitted. This may
be confusing or appear sloppy to users of the system.

This 25-second video demonstrates the undesired behavior on a clean install:

ckeditor_html_flash.webm

Why Does This Happen?

This is caused by the editor being destroyed while "detaching", which is not needed
during a page submit, only when switching between other text formats & editors. The "destroy"
command removes the editor, leaving a plain textarea with visible HTML.

There is currently an issue in core which addresses the problem. This module is meant to be a
workaround until that PR is merged (if accepted). The core issue URL is:
backdrop/backdrop-issues#7149. If the related PR
is ever merged with core, this module will be marked as deprecated.

How This Module Works

This module is very simple. When a form (which is using a text_format element) is submitted, we set a
javascript variable.

Also, we override core's code for "detach" of CKEditor5 to first check for this javascript variable. If
the form is in the process of being submitted, we do not destroy the editor, thereby preventing
the flash of plain HTML.

Usage

Once enabled, this module requires no special actions to take effect. If it detects an element in a form
which might be using CKEditor, it will automatically make use of the workaround code.

Installation

• Install this module using the official Backdrop CMS instructions at
  https://backdropcms.org/guide/modules

Current Maintainers

• Richard Peacock (original creator for Backdrop CMS)

License

This project is GPL v2 software. See the LICENSE.txt file in this directory for
complete text.