How can I exclude a subject in a Mosaic content listing tile?

Plone Support
4

I use a boolean Field via Behavior for "News Item", if this checked then the News is a "Sticky News" and pinned on top of site in a viewlet.
I think it can be adapted for "isEmpty" or "shouldNotContain" or whatever.

You need a catalog index

<!--catalog.xml-->
  <index
    name="is_sticky"
    meta_type="BooleanIndex">
    <indexed_attr value="is_sticky" />
  </index>

You need a indexer

<!--indexer.zcml-->
<configure xmlns="http://namespaces.zope.org/zope">
  <adapter
    factory=".my_indexer.sticky_news"
    name="is_sticky" />
</configure>

# my_indexer.py
# -*- coding: utf-8 -*-
from plone.app.contenttypes.interfaces import INewsItem
from plone.indexer import indexer
from my.addon.behaviors.sticky_news import StickyNews

@indexer(INewsItem)
def sticky_news(obj):
    """Calculate and return the value for the indexer"""
    sticky = StickyNews(obj)
    if not sticky:
        return False
    return sticky.enable

You need a querystring definition

<!--registry.xml-->
<records
  interface="plone.app.querystring.interfaces.IQueryField"
  prefix="plone.app.querystring.field.is_sticky">
  <value
    key="title"
    i18n:translate="">Sticky News</value>
  <value key="description">check is the sticky news behavior available and set</value>
  <value key="enabled">True</value>
  <value key="sortable">False</value>
  <value key="operations">
    <element>plone.app.querystring.operation.boolean.isTrue</element>
    <element>plone.app.querystring.operation.boolean.isFalse</element>
  </value>
  <value key="group">Custom</value>
</records>

with all these steps, a filter in a collection is available.