Entity display processor

This module provides a new plugin type that enhances the regular display of entities.

Features

The module introduces a plugin type "Entity display processor".
The plugin can be chosen as part of an entity view mode.

This way, what used to be one-off implementations of hook_entity_view_alter() in your project can be turned into reusable plugins, and possibly published as part of contributed modules.

Possible effects that could be achieved:
- Add a CSS effect to the rendered entity: Shadow, background color, etc.
- Add a custom CSS class to the entity's html element.
- Display the entity in an expand/collapse box.
- Apply a dynamic effect that depends on values in the entity. E.g. a colored frame, where the color is coming from a field value.

Only few such plugins are published as part of this module.
The idea is to create more plugins as part of your specific project, theme, or in-house ecosystem.

Post-Installation

After installation, go to do e.g. `/admin/structure/types/manage/page/display/teaser`.
(assuming that a content type 'page' exists, with a view mode 'teaser')
At the bottom of the form, you can choose and configure up to one entity display processor plugin.
Later, when viewing the entity in the given view mode, the effect from the plugin will be applied.

Similar projects

You can achieve similar effects with Display Suite, or with core layout builder, if you have a layout that has the desired effect. However, with this module, you can add an additional effect that is independent of the layout.