Implementing presentations which include standalone interactive elements

Aim

• One “Next” button on the Stream Deck drives everything.
• If the current slide is an interactive iframe, that same button should first advance the iframe through its own internal steps; only when the iframe reports “I’m finished” does the master deck move on.
• You also need a separate “Previous” button that always jumps to the previous master slide (no need to rewind the iframe’s micro-steps).

⠀The cleanest way to do this is to keep all navigation logic in the parent deck and make the Stream Deck talk only to that parent. The parent in turn negotiates with each iframe over a tiny postMessage protocol.