Support popup-window context on the sign-up page (/account/create)

[Yndira-E]

Context

The marketing site is prototyping opening /account/create in a small popup window instead of navigating away, to lower friction for the free-trial sign-up flow. Full discussion here: https://flowfuse.slack.com/archives/C032Q63FGG1/p1786398271612039

The popup behavior itself is handled entirely client-side on the marketing site (a click-interceptor script). Nothing about how /account/create is normally reached (e.g. from the login page) changes. This issue covers what still needs to happen on the product side for that popup context to work well.

What's needed

1. Conditional layout based on popup context

When the page detects it was opened via window.open() (i.e. window.opener is set):

• Hide the left-hand marketing column (too cramped for a ~420px-wide popup).
• Show a short line of copy in the "above the form" section instead (this section exists in admin settings today but is currently unused/empty). Suggested copy: "Start building modern industrial applications today — for free." (Requested via https://github.com/FlowFuse/CloudProject/issues/1538)
• In a normal full-tab context, keep today's behavior unchanged (left column shown as configured) and hide the copy above the form.

2. Hand off to a full tab once past the initial form step

The popup should only ever show the sign-up form itself (step 0). Once the user is past that: successfully registered, mid-verification, or if they already have an active session and land on this URL some other way, the page should open a full tab and close the popup, rather than continuing to render everything (verification screen, or worse, the whole platform) inside the small window.

Epic/Story

No response

Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate

[knolleary]

Rather than window.opener, a more robust approach would be to use a query-parameter in the url to enable this behaviour. That way we know explicitly to be in this pop-up mode.

We'd still use window.opener to reference the opening window context for opening the follow-up page after the initial form submission passes and the pop-up is closed.

[Yndira-E]

That makes sense, how about ?context=popup? Already implemented on the website PR (FlowFuse/website#5616) if you want to take a look.

[allthedoll]

@n-lark do you have bandwidth for this today?

[knolleary]

Some context. Here are the two relevant settings in Admin Settings.

The first is the oneline that is shown above the sign-up form. The second is the left-hand column content.

One nit with the proposal; explicitly hiding the one-liner when not in pop-up mode would be a change in behaviour - any self-hosted with a one-liner set would no longer see it. I'm not sure how excited to get about that as a change.

[n-lark]

Hey @Yndira-E @allthedoll PR is up: #8228

Here's what it does when /account/create is opened with ?context=popup:

• Hides the left marketing column
• Hands off to a full tab once past the form (registration success, already-authenticated load, and Google/SSO)

On @knolleary's concern, I made the call to leave the "above the form" one-liner alone. It still shows whenever an admin has configured it, so no self-hosted install loses its banner; nothing gets hidden based on mode.

⚠️ We will still need someone to set Start building modern industrial applications today — for free. since I don't have access to admin settings in our platform.

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One thing to note for the marketing PR: the handoff navigates the opener tab (then closes the popup), so it only works when the page is opened via window.open(...) and window.opener is set. Just visiting ?context=popup as a normal URL won't trigger it — make sure the site opens it as a real popup.

[allthedoll]

Cc @KristopherLeads @JoycePlaysFootball since yndira is ooo