Pad Frame Duration

1// pad-frame-duration.mjs — keeps a frame's own #root/clip data-duration in
2// sync with the padded index.html wrapper duration transitions.mjs computes.
3//
4// The frame's OWN internal file declares its #root/clip data-duration to the
5// STORYBOARD's content-only length (frame-worker.md: duration is "fixed
6// upstream"). When an outgoing transition pads the index.html WRAPPER's
7// data-duration to cover the transition tail, the frame's own internal
8// duration is left short — the render engine clip-gates the sub-composition's
9// visible content at that shorter value, so content vanishes abruptly at
10// content-end instead of fading gracefully through the wrapper's extended
11// fade-out tween. Pad the frame's own file to match so both durations agree.
12
13import { readFileSync, writeFileSync } from "node:fs";
14import { resolve } from "node:path";
15
16export function padFrameInternalDuration(hyperframesDir, frameSrc, frameId, newDuration) {
17  const framePath = resolve(hyperframesDir, frameSrc);
18  let html;
19  try {
20    html = readFileSync(framePath, "utf8");
21  } catch (err) {
22    if (err?.code === "ENOENT") return;
23    throw err;
24  }
25  const tagRe = /<[a-z][\w:-]*\s[^<>]*?>/gi;
26  let m;
27  while ((m = tagRe.exec(html)) !== null) {
28    const tag = m[0];
29    if (!tag.includes(`data-composition-id="${frameId}"`)) continue;
30    if (!/data-duration="[\d.]+"/.test(tag)) continue;
31    const newTag = tag.replace(/data-duration="[\d.]+"/, `data-duration="${newDuration}"`);
32    if (newTag === tag) return;
33    writeFileSync(framePath, html.slice(0, m.index) + newTag + html.slice(m.index + tag.length));
34    return;
35  }
36}