www programming

And about the [size=150]possibility to push real phpBB urls[/size]:
i tested that [size=150]it is possible and works[/size], but it is required that the wordpress and phpBB are into DOMAIN/DOMAIN or same SUBDOMAIN/SUBDOMAIN.
So if wordpress and phpBB are on same domain, or both on same subdomain, it is possible.
While it is not possible into domain/subdomain.

ex: wp at mysite.com and phpBB at mysub.mysite.com [size=150]NOT possible[/size]
ex: wp at mysite.com and phpBB at mysite.com/forum [size=150]possible[/size]
ex: wp at mysub.mysite.com and phpBB at mysub.mysite.com/forum [size=150]possible[/size]

The unique problem, is this:
the address bar is pushed with real phpBB urls, and also the browser's history with the same value.
When an intentional browser's page refresh happen due to an intentional user's action that go to reload the WP parent page, the browser's history is broken exactly like it is now into the actual and still not updated base64.
Both will be provided, anyway the above new base64 works very fine and i will apply also, if possible, another good feature
https://www.axew3.com/w3/forums/viewtopic.php?p=6597#p6597

After, i've return over this complicate thing.
I've get the following possible working results.

Using the [c]history.replaceState[/c] in place of [c]history.pushState[/c] and some other changes into the javascript that manage the iframe parent/child messages, and another php trick on same page-forum code (or the shortcode code when it will be added) it is possible to achieve the follow:
the parent, correctly show into the address bar, the actual iframe encoded phpBB url where it is on.
On parent reload so, the right phpBB page will be naturally presented, and plus, moving again back/forward with the browser, it will be ever and again on the right place. Very nice!

The other is this:
https://www.axew3.com/w3/forums/viewtopic.php?p=6605#p6605

So finally yes, i was not sure of, but now i can say that probably i've find out the way to:

[size=120]do not push URL's[/size] into the parent WP address page.
[size=120]let reload the page into the same[/size], when an intentional browser's reload of the parent WP page occur.

But [b]the most important that the new way do[/b] is this:
when the parent WP page is reloaded, into the base64 old code, [size=120]the browser's history is lost[/size].
Once the parent WP page has been reloaded, when you click into the browser's back button, the [i]next/prev[/i] page that will show isn't anymore the one expected or worst, there is no one navigable, even if the history result to be populated. The browser's history is broken.
[color=#BF0040][size=120]With the new code, this old and very notable issue, has been resolved.[/size][/color]
And several more. There will be practically no difference on browsing the forum into the iframe or at real URL.
I feel like this into my local test.

There is a last issue that i would like to fix, so then the pro-template integration code will be released.
Stay tuned lovely people!

The problem about the parent WP reload and popup confirmation that you rightly reported, when the login/out is done into the iframed phpBB, has been fixed:
https://www.axew3.com/w3p/board/
It just do not fire anymore when a login/out into the iframed phpBB occur.
Any other eventual event conflicting with the correct parent reload (which i cannot imagine at moment what other could be, but surely could exist someone else) can be fixed in the same experimented (and working) way.

Ps. why did you not changed, into your site, the custom fancy URL (pushed URLs into the address bar) to be something like
[c].../forum/?surfing=dmlld3RvcGljLnBocD9wPTY1NTYjcDY1NTY=[/c]
and you're using the default [i]w3[/i] [c]....forum/?w3=dmlld3RvcGljLnBocD9wPTY1NTYjcDY1NTY=[/c]
??

When i try to login, it present the dialog, then if you choose to not leave the page, it is obvious that then the WP parent page will not reload, and the user will result logged into phpBB and apparently not in WP.
But it could be maybe fixed, so to avoid the confirmation popup when the login/out occur.
It is a good point that should be fixed if possible (or in effect it would be not so nice maybe).

P.s and in any case it will never substitute the actual and default base64, it will be just a possible another way not included, that can be added.
I am not also totally sure that it will decently work.

The possible feature that will be possible to be added, is the draggable [i]Reload forum (iframe) button[/i]:
having it on WP parent or phpBB is very easy and require few lines of code.
But as said, and like before, it will not included by default.

Without reloading WordPress after logging in through phpBB, the WordPress site still thinks you are not logged in.

I already tested it here. In my case, Safari asked me if I wanted to stay on the page or leave the page (which means reloading WordPress) when I used the phpBB login.

I understand the idea behind it, but especially for users like me, where parts of the WordPress menu are only visible after reloading WordPress while using the phpBB login, this template isn't very useful.