Problem: Switching slides reset iframe.src each time, causing visible
flicker (white flash → load → render) on every navigation.
Solution: load each preview iframe ONCE, then use postMessage for all
subsequent slide changes. The iframe stays mounted; only .is-active
class toggles between slides inside it.
Changes:
- runtime.js preview mode: now exposes a showSlide() function and
listens for window.message events of type 'preview-goto'. Also
posts 'preview-ready' to parent on init so the presenter window
knows when each iframe is loaded.
- presenter window: tracks iframeReady state per iframe; first frame
renders via iframe.src = ?preview=N (one-time), all subsequent
navigation goes through postPreviewGoto() → postMessage. Notes,
meta, and timer update directly without touching iframes.
- Init no longer calls update(idx) which used to reset iframe.src;
instead inits notes/meta/count once and lets the load→ready flow
populate previews.
Docs synced to match new architecture:
- SKILL.md: describes 4 magnetic cards, draggable/resizable, with
the iframe ?preview=N pattern explained for AI consumers
- references/presenter-mode.md: updated ASCII diagram to show 4
cards, removed old 58%/35% layout description, added explanation
for why previews are pixel-perfect (iframe loads same HTML) and
why navigation is flicker-free (postMessage, not reload)
- presenter-mode-reveal README: updated 4-card description
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