Usage

The five things Stop Sign says

It says	It means	Colour
"Dana Reyes is editing this right now."	Somebody else has typed. If you both save, one of you loses the work	Red
"Dana Reyes has this open."	Somebody else is on the screen but has not typed	Amber
"Dana Reyes saved this while you had it open."	What you are looking at is out of date. Saving would put the old version back	Red
"You have this open in another tab."	Two of your own windows will overwrite each other	Blue
"Dana Reyes has this locked."	Read-only until they finish, or until you take over	Red

The own-tab warning is a notice rather than a danger, and it does not interrupt saving. It is still your own work either way, and a modal in front of every save because you happen to have two windows open is a modal you would learn to click through. The banner is enough.

The save guard

When somebody else is actively editing, or the element changed while you had it open, saving stops and asks:

Hold on Dana Reyes is editing this right now. If you both save, one of you loses the work.

Go back Save anyway

When the element is stale there is a third button, Reload the latest, which discards nothing — it reloads so you can see what changed before deciding.

Every one of those three choices is recorded. That is the point of the history: the interesting number is not how many collisions happened, it is how many were clicked straight through.

Index badges

An element that somebody is inside gets a dot on its chip, on element indexes and in relation fields. It is a snapshot from when the page rendered, not a live feed — the alternative is polling from every index screen in the control panel, which is a lot of requests to answer a question that is only ever "probably not".

Utilities → Stop Sign

Three things:

• Open right now — who is in what, viewing or editing, and since when.
• Locks held — only shown when locking is on. Includes a Release every lock button.
• Collisions — the history, with a summary of outcomes across the retention window.

Console

php craft stopsign/status            # settings, who is open, what is locked
php craft stopsign/unlock            # clear expired locks
php craft stopsign/unlock --all      # clear every lock — the kill switch
php craft stopsign/prune             # trim presence, locks, history and the save ledger
php craft stopsign/history --days=30 # collisions, and how many were clicked through

stopsign/prune runs automatically as part of Craft's garbage collection; the command is there for when you want it now.

Twig

{# Is anybody inside this element right now? #}
{% if craft.stopsign.isOccupied(entry) %}
    <span class="busy">Somebody is working on this</span>
{% endif %}

{# A dashboard of everything open #}
{% for row in craft.stopsign.board() %}
    {{ row.userName }} — {{ row.dirty ? 'editing' : 'viewing' }} #{{ row.elementId }}
{% endfor %}

{# Live locks #}
{% for lock in craft.stopsign.locks() %}
    {{ lock.userName }} holds #{{ lock.elementId }}
{% endfor %}

{# Collision history, optionally for one element #}
{% for row in craft.stopsign.history(20, entry.id) %}
    {{ row.dateCreated|datetime }} — {{ row.userName }} {{ row.outcome }}
{% endfor %}

isOccupied() answers from a single query memoised for the whole request, so calling it in a loop over a hundred elements costs one query, not a hundred.