poster/render_hotspots.py

#!/usr/bin/env python3
"""Render poster.html to a PNG at print size and extract bounding boxes for
every element carrying data-logbook-target, for building poster_embed.html."""
import json
import re
import sys
from pathlib import Path

from playwright.sync_api import sync_playwright

POSTER = Path(sys.argv[1] if len(sys.argv) > 1 else "poster.html").resolve()
OUT_PNG = Path(sys.argv[2] if len(sys.argv) > 2 else "poster.png").resolve()
OUT_JSON = Path(sys.argv[3] if len(sys.argv) > 3 else "hotspots.json").resolve()

text = POSTER.read_text()
m = re.search(r"@page\s*{\s*size:\s*([\d.]+)in\s+([\d.]+)in", text)
if not m:
    raise SystemExit("Could not find @page size in poster.html")
w_in, h_in = float(m.group(1)), float(m.group(2))
DPI = 150
W, H = round(w_in * DPI), round(h_in * DPI)

with sync_playwright() as p:
    browser = p.chromium.launch()
    page = browser.new_page(viewport={"width": W, "height": H}, device_scale_factor=1)
    page.emulate_media(media="print")
    page.goto(POSTER.as_uri())
    page.wait_for_timeout(500)
    try:
        page.wait_for_function("window.MathJax && MathJax.startup && MathJax.startup.document", timeout=3000)
        page.wait_for_timeout(300)
    except Exception:
        pass

    poster_el = page.query_selector('[data-measure-role="poster"]')
    poster_box = poster_el.bounding_box()

    hotspots = []
    for el in page.query_selector_all("[data-logbook-target]"):
        slug = el.get_attribute("data-logbook-target")
        box = el.bounding_box()
        if not box:
            continue
        hotspots.append(
            {
                "slug": slug,
                "left_pct": 100 * (box["x"] - poster_box["x"]) / poster_box["width"],
                "top_pct": 100 * (box["y"] - poster_box["y"]) / poster_box["height"],
                "width_pct": 100 * box["width"] / poster_box["width"],
                "height_pct": 100 * box["height"] / poster_box["height"],
            }
        )

    page.screenshot(path=str(OUT_PNG), full_page=False, clip=poster_box)
    browser.close()

OUT_JSON.write_text(json.dumps({"hotspots": hotspots, "png_w": W, "png_h": H}, indent=2))
print(f"Wrote {OUT_PNG} and {OUT_JSON} ({len(hotspots)} hotspots)")