Files
hyperframes/packages/engine/src
miga-heygenandMiguel Ángel d7285e414b fix(engine): preserve composition root background in alpha exports (#3976)
* fix(engine): preserve composition root background in alpha exports

initTransparentBackground() forced html, body, AND any
[data-composition-id] element (the composition root, or a nested
sub-composition root) to transparent for every alpha-carrying capture
session. That's correct for the HDR two-pass layered DOM pass, where
the HDR video itself is the backdrop — but for a plain alpha export
(MOV ProRes4444, webm+alpha) of a normal composition, an author's own
background painted on the root is real, intentional content, and it
was being silently dropped.

Add CaptureOptions.clearCompositionRootBackground, threaded through
session.options into every general-session call site (default false —
preserve the root's authored background). The two HDR-layered-DOM-
session call sites set it to true, keeping their existing (correct)
behavior. initTransparentBackground's injected stylesheet is now
idempotently rewritten rather than insert-once/skip, so a caller's
choice is never silently ignored by an earlier call on the same page.

Add a producer test fixture + transparency-test.ts check proving a
composition root's authored background survives into alpha output,
plus unit tests for both flag values and the rewrite-on-repeat-call
behavior directly.
Co-Authored-By: Miguel Ángel <miguel.sierra@heygen.com>

* test(producer): register the new transparency fixture with the shard planner

transparency-regression-root-bg is exercised by transparency-test.ts
directly (asserts a real alpha channel), not by the sharded regression
harness, same as its sibling transparency-regression. The shard
planner hard-fails on any fixture directory it doesn't recognize as
either scheduled or explicitly excluded, so register it in the
excluded list with the same reason as its sibling.
Co-Authored-By: Miguel Ángel <miguel.sierra@heygen.com>

* fix(engine): restore explicit transparent-background call for HDR layered sessions

The previous commit removed the two HDR-layered-DOM-session call
sites' own explicit initTransparentBackground() call, relying on
initializeSession()'s internal call (gated behind
session.options.format === "png") plus a new
clearCompositionRootBackground session option.

That was wrong: a plain HDR render's own DOM session captures
"jpeg", not "png" — the final HDR MP4/HEVC output doesn't itself
carry an alpha channel, only the layered-compositing step does. So
initializeSession()'s internal call never fired at all for this
common case, and the HDR video layer never got a transparent DOM
backdrop to composite into.

Reproduced directly against the hdr-regression fixture (part of the
regression-shards CI suite): a real local render showed a severe
PSNR collapse (~8-56dB) in the "Window B: z-order sandwich" segment,
where a DOM element behind the HDR video, the video itself, and a
translucent DOM overlay in front all need correct z-ordering — with
the composition root's own background no longer cleared, it painted
solid over the video slot instead of letting the video composite
through. Confirmed via bisection: reverting to the prior commit's
files reproduces 0 failed frames (passing); the removed-call version
reproduces the exact failure; restoring the explicit calls fixes it
again (100/100 checkpoints, 0 failed frames).

Restore the explicit, unconditional call in both HDR call sites,
right after initializeSession(). clearCompositionRootBackground still
does its job for the general/plain-alpha-export path (frameCapture.ts),
which is unaffected by this fix.
Co-Authored-By: Miguel Ángel <miguel.sierra@heygen.com>

* refactor(engine): let the HDR layered pass own composition-root clearing

Drop the CaptureOptions.clearCompositionRootBackground field: every HDR layered
DOM session already calls initTransparentBackground right after init, so that
call is the one owner. Engine paths use the default, which keeps root backgrounds.

* chore(producer): drop comment additions the comment ratchet rejects

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Co-authored-by: Miguel Ángel <miguel.sierra@heygen.com>
2026-10-02 06:51:31 -07:00
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