Datasets:

figma-ai
/

motion-graphics-bench

"""Measure SVG frames in Chromium and return per-element animation data."""

from __future__ import annotations

import json
import os
import subprocess
import sys
import tempfile
from typing import Any, Dict, List, Optional, Sequence


_SELF = os.path.abspath(__file__)
_OBSERVER = os.path.join(os.path.dirname(_SELF), "observer.js")

# Paint and clipping styles are retained even when constant.
STYLE_FLOOR = (
    "opacity",
    "display",
    "visibility",
    "fill",
    "fill-opacity",
    "stroke",
    "stroke-width",
    "stroke-opacity",
    "stroke-linecap",
    "stroke-dasharray",
    "stroke-dashoffset",
    "clip-path",
    "mask-image",
    "mask-mode",
    "mask-composite",
    "filter",
    "marker-start",
    "marker-mid",
    "marker-end",
)

# Definition geometry and paint remain available even when constant.
RESOURCE_STYLE_FLOOR = STYLE_FLOOR + (
    "color",
    "fill-rule",
    "stroke-linejoin",
    "stroke-miterlimit",
    "vector-effect",
    "clip-rule",
    "mask-type",
    "stop-color",
    "stop-opacity",
    "flood-color",
    "flood-opacity",
    "lighting-color",
    "color-interpolation",
    "color-interpolation-filters",
    "transform",
    "transform-origin",
    "transform-box",
    "d",
    "x",
    "y",
    "cx",
    "cy",
    "r",
    "rx",
    "ry",
    "width",
    "height",
)

ALL_STYLES = ("*",)

# Style changes between sampled frames may be missed; 0 reads all properties per frame.
STYLE_SAMPLE_FRAMES = 10

FACT_COLUMNS = (
    "ctm",
    "own",
    "bbox",
    "length",
    "ends",
    "contour",
    "stroke_width",
    "visible_fraction",
    "clip_box",
    "mask_box",
    "resource_inputs",
    "tag",
    "parent",
    "order",
)

COLUMN_DOC = {
    "ctm": "where the element sits, as six numbers, in the root SVG's own user space",
    "own": "its own transform alone, without its ancestors' -- `ctm` composes the whole chain",
    "bbox": "its own extent (x, y, w, h) in its own coordinates",
    "length": "the outline length of a shape that has one, and `None` for a shape that has none",
    "ends": "where its outline begins and ends, for telling a draw-on from a move",
    "contour": "32 samples along its outline, already placed in root space",
    "stroke_width": "its painted stroke width in root space; exact under uniform scale",
    "visible_fraction": "the sampled painted fraction kept by supported clips and binary alpha masks",
    "clip_box": "the box a clip leaves visible, already placed in root space",
    "mask_box": "the box a mask's content covers, already placed in root space. Its shape, not its paint",
    "resource_inputs": (
        "referenced SVG definition inputs, keyed by URL/href; each has tag, attrs, effective style and children, "
        "with linked definitions in the same map. Missing/external references are None; no references is {}. "
        "Read with get_column(matrix, path, 'resource_inputs'); group-owned effects stay on the parent row. "
        "These are source inputs, not resolved instance geometry or final visible paint; a difference need not change pixels"
    ),
    "tag": "what it is: `path`, `g`, `rect`",
    "parent": "the path of the element that contains it",
    "order": "where it falls among its siblings in the document",
}


def _observer_source() -> str:
    with open(_OBSERVER, encoding="utf-8") as f:
        return f.read()


def _render(page, svg: str) -> None:
    page.set_content(f"<!doctype html><html><body style='margin:0'>{svg}</body></html>", wait_until="load")


def _observe(page, js: str, styles, baseline, reuse_outline: bool = True, resource_styles=None):
    """Observe one frame, restoring the style baseline after a cleared browser context."""
    opts = {
        "wantDiff": baseline is not None,
        "styles": styles,
        "resourceStyles": resource_styles,
        "reuseOutline": reuse_outline,
    }
    got = page.evaluate(js, opts)
    if got.get("needsBaseline"):
        page.evaluate("(b) => { window.__baseline = b; }", baseline)
        got = page.evaluate(js, {**opts, "wantDiff": True})
    assert "error" not in got, got["error"]
    return got


def _spread(total: int, n: int) -> List[int]:
    """Select evenly spaced frame indices, including endpoints when n permits."""
    if n <= 0 or n >= total:
        return list(range(total))
    if n == 1:
        return [0]
    return sorted({round(i * (total - 1) / (n - 1)) for i in range(n)})


def _resource_nodes(resources):
    """Referenced nodes keyed by reference and child position, independently of their drawable owners."""
    for reference, node in resources.items():
        if node is not None:
            yield (reference,), node
            for path, child in _resource_nodes(dict(enumerate(node["children"]))):
                yield (reference, *path), child


def _moving_styles(page, js: str, frames: List[str], sampled: Sequence[int]) -> tuple[set, set]:
    """Find styles that vary across sampled frames; unsampled changes may be missed."""
    moved: set = set()
    resource_moved: set = set()
    resource_baseline: dict = {}
    baseline: Dict[str, Dict[str, str]] | None = None
    born: Dict[str, Dict[str, str]] = {}
    for i in sampled:
        _render(page, frames[i])
        got = _observe(page, js, None, baseline)
        rows = {r["path"]: r for r in got["rows"]}
        resources = {ref: node for row in rows.values() for ref, node in row["resource_inputs"].items()}
        for path, node in _resource_nodes(resources):
            style = node["style"]
            base = resource_baseline.setdefault(path, style)
            resource_moved.update(k for k in base.keys() | style.keys() if base.get(k) != style.get(k))
        if baseline is None:
            baseline = {path: r["style"] for path, r in rows.items()}
            page.evaluate("(b) => { window.__baseline = b; }", baseline)
            continue
        for path, row in rows.items():
            style = row["style"]
            if path in baseline:
                moved.update(style)
            elif path in born:
                moved.update(k for k, v in style.items() if born[path].get(k) != v)
            else:
                born[path] = style
    return moved, resource_moved


def _measure_in_process(
    frames: List[str],
    viewport: int = 1000,
    fps: float | None = None,
    style_floor: Sequence[str] = STYLE_FLOOR,
    frame_indices: Sequence[int] | None = None,
    style_sample_frames: int = STYLE_SAMPLE_FRAMES,
    reuse_outline: bool = True,
) -> Dict[str, Any]:
    """Browser measurement worker; use measure to avoid conflicts with an existing event loop."""
    from playwright.sync_api import sync_playwright

    js = _observer_source()
    per_frame: List[Dict[str, Any]] = []
    canvases: List[Any] = []
    with sync_playwright() as p:
        browser = p.chromium.launch(args=["--disable-dev-shm-usage"])
        version = browser.version
        page = browser.new_page(viewport={"width": viewport, "height": viewport})

        styles: Optional[List[str]] = None
        resource_styles: Optional[List[str]] = None
        if tuple(style_floor) != ALL_STYLES and style_sample_frames > 0 and len(frames) > 1:
            sampled = _spread(len(frames), style_sample_frames)
            moved, resource_moved = _moving_styles(page, js, frames, sampled)
            styles = sorted(set(style_floor) | moved)
            resource_styles = sorted(set(RESOURCE_STYLE_FLOOR) | set(style_floor) | resource_moved)
            page.evaluate("() => { window.__baseline = undefined; }")

        baseline: Dict[str, Dict[str, str]] | None = None
        for svg in frames:
            _render(page, svg)
            got = _observe(page, js, styles, baseline, reuse_outline, resource_styles)
            rows = {r["path"]: r for r in got["rows"]}
            if baseline is None:
                baseline = {path: r["style"] for path, r in rows.items()}
                page.evaluate("(b) => { window.__baseline = b; }", baseline)
            per_frame.append(rows)
            canvases.append(got["canvas"])
        browser.close()

    return _assemble(per_frame, canvases, version, baseline or {}, fps, style_floor, frame_indices, styles)


def measure(
    frames: List[str],
    viewport: int = 1000,
    fps: float | None = None,
    style_floor: Sequence[str] = STYLE_FLOOR,
    frame_indices: Optional[Sequence[int]] = None,
    timeout: float = 900.0,
    style_sample_frames: int = STYLE_SAMPLE_FRAMES,
    reuse_outline: bool = True,
) -> Dict[str, Any]:
    """Measure frames in a child process. Coordinates use root SVG units; fps and frame_indices record caller-supplied timing."""
    if not frames:
        raise ValueError("no frames to measure: an animation matrix needs at least one frame")
    with tempfile.TemporaryDirectory() as tmp:
        given, produced = os.path.join(tmp, "given.json"), os.path.join(tmp, "matrix.json")
        with open(given, "w") as f:
            json.dump(
                {
                    "frames": list(frames),
                    "viewport": viewport,
                    "fps": fps,
                    "style_floor": list(style_floor),
                    "frame_indices": list(frame_indices) if frame_indices is not None else None,
                    "style_sample_frames": style_sample_frames,
                    "reuse_outline": reuse_outline,
                },
                f,
            )
        try:
            proc = subprocess.run(
                [sys.executable, _SELF, given, produced],
                capture_output=True,
                text=True,
                timeout=timeout,
            )
        except subprocess.TimeoutExpired:
            raise RuntimeError(f"measuring {len(frames)} frames timed out after {timeout:.0f}s") from None
        if not os.path.exists(produced):
            raise RuntimeError(f"measuring failed (exit {proc.returncode}): {(proc.stderr or '')[-1500:]}")
        with open(produced) as f:
            return json.load(f)


def _assemble(
    per_frame,
    canvases,
    version: str,
    baseline,
    fps: float | None = None,
    style_floor: Sequence[str] = STYLE_FLOOR,
    frame_indices: Sequence[int] | None = None,
    styles_measured: Sequence[str] | None = None,
) -> Dict[str, Any]:
    """Split observations into constant and per-frame columns; absent nodes contribute None."""
    n = len(per_frame)
    if frame_indices is None:
        frame_indices = list(range(n))
    elif len(frame_indices) != n:
        raise ValueError(f"{len(frame_indices)} frame indices for {n} frames: they name the frames measured")
    paths: List[str] = []
    for rows in per_frame:
        for path in rows:
            if path not in paths:
                paths.append(path)

    if tuple(style_floor) != ALL_STYLES:
        resource_seen: dict = {}
        for rows in per_frame:
            for row in rows.values():
                for resource_path, node in _resource_nodes(row.get("resource_inputs", {})):
                    resource_seen.setdefault(resource_path, []).append(node)
        kept: dict = {}
        for nodes in resource_seen.values():
            base = nodes[0]["style"]
            keep = set(RESOURCE_STYLE_FLOOR) | set(style_floor)
            keep.update(
                k for node in nodes for k in base.keys() | node["style"].keys() if base.get(k) != node["style"].get(k)
            )
            for node in nodes:
                kept.setdefault(id(node), (node, set()))[1].update(keep)
        # Shared definitions must be discovered before their styles are pruned.
        for node, keep in kept.values():
            node["style"] = {k: v for k, v in node["style"].items() if k in keep}

    objects: Dict[str, Any] = {}
    for path in paths:
        seen = [rows.get(path) for rows in per_frame]
        cells: Dict[str, List[Any]] = {}
        for key in FACT_COLUMNS:
            cells[key] = [None if r is None else r.get(key) for r in seen]

        attr_names = sorted({k for r in seen if r for k in r["attrs"]})
        for name in attr_names:
            cells[f"attr.{name}"] = [None if r is None else r["attrs"].get(name) for r in seen]

        # Missing style entries reuse the frame-zero baseline.
        base = baseline.get(path, {})
        style_names = set(base) | {k for r in seen if r for k in r["style"]}
        for name in sorted(style_names):
            cells[f"style.{name}"] = [None if r is None else r["style"].get(name, base.get(name)) for r in seen]

        const, series = {}, {}
        for key, values in cells.items():
            present = [v for v in values if v is not None]
            if present and all(v == present[0] for v in present) and len(present) == n:
                const[key] = present[0]
            elif present:
                series[key] = values
            else:
                const[key] = None
        if tuple(style_floor) != ALL_STYLES:
            const = {k: v for k, v in const.items() if not k.startswith("style.") or k[len("style.") :] in style_floor}
        objects[path] = {"const": const, "series": series}

    canvas_const = all(c == canvases[0] for c in canvases)
    return {
        "info": {
            "frames": n,
            "fps": fps,
            # Duration spans the intervals between frames, not the number of samples.
            "duration": round((n - 1) / fps, 6) if fps else None,
            "chromium": version,
            "source_frames": list(frame_indices),
            "canvas": canvases[0] if canvas_const else None,
            "canvas_series": None if canvas_const else canvases,
            "aliased_rows": _aliased_rows(objects),
            # None means every style property was measured.
            "styles_measured": list(styles_measured) if styles_measured is not None else None,
        },
        "objects": objects,
    }


def _aliased_rows(objects: Dict[str, Any]) -> List[str]:
    """Paths with uncertain identity after sibling changes, including affected descendants."""
    aliases = set()
    siblings: Dict[str, List[str]] = {}
    identifiers = {}
    anonymous = set()
    for path, obj in objects.items():
        for column in ("tag", "attr.id"):
            if len({v for v in obj["series"].get(column, []) if v}) > 1:
                aliases.add(path)
        tags = obj["series"].get("tag", [])
        ids = obj["series"].get("attr.id", [obj["const"].get("attr.id")] * max(1, len(tags)))
        identifiers[path] = {v for v in ids if v}
        tags = tags or [obj["const"].get("tag")] * len(ids)
        if any(not identity and tag is not None for identity, tag in zip(ids, tags)):
            anonymous.add(path)
        siblings.setdefault(path.rsplit("[", 1)[0], []).append(path)

    for paths in siblings.values():
        if len(paths) < 2 or not any(None in objects[p]["series"].get("tag", []) for p in paths):
            continue
        for path in paths:
            tags = objects[path]["series"].get("tag", [])
            if tags and sum(t is not None for t in tags) < 2:
                continue
            if path in anonymous or any(identifiers[path] & identifiers[p] for p in paths if p != path):
                aliases.add(path)

    # ponytail: Equal-count anonymous replacements cannot be identified from these observations; stable IDs are needed for that.
    return [p for p in objects if p in aliases or any(p.startswith(a + "/") for a in aliases)]


if __name__ == "__main__":
    with open(sys.argv[1]) as f:
        asked = json.load(f)
    matrix = _measure_in_process(
        asked["frames"],
        viewport=asked["viewport"],
        fps=asked["fps"],
        style_floor=asked["style_floor"],
        frame_indices=asked["frame_indices"],
        style_sample_frames=asked.get("style_sample_frames", STYLE_SAMPLE_FRAMES),
        reuse_outline=asked.get("reuse_outline", True),
    )
    with open(sys.argv[2], "w") as f:
        json.dump(matrix, f)

	"""Measure SVG frames in Chromium and return per-element animation data."""

	from __future__ import annotations

	import json
	import os
	import subprocess
	import sys
	import tempfile
	from typing import Any, Dict, List, Optional, Sequence


	_SELF = os.path.abspath(__file__)
	_OBSERVER = os.path.join(os.path.dirname(_SELF), "observer.js")

	# Paint and clipping styles are retained even when constant.
	STYLE_FLOOR = (
	"opacity",
	"display",
	"visibility",
	"fill",
	"fill-opacity",
	"stroke",
	"stroke-width",
	"stroke-opacity",
	"stroke-linecap",
	"stroke-dasharray",
	"stroke-dashoffset",
	"clip-path",
	"mask-image",
	"mask-mode",
	"mask-composite",
	"filter",
	"marker-start",
	"marker-mid",
	"marker-end",
	)

	# Definition geometry and paint remain available even when constant.
	RESOURCE_STYLE_FLOOR = STYLE_FLOOR + (
	"color",
	"fill-rule",
	"stroke-linejoin",
	"stroke-miterlimit",
	"vector-effect",
	"clip-rule",
	"mask-type",
	"stop-color",
	"stop-opacity",
	"flood-color",
	"flood-opacity",
	"lighting-color",
	"color-interpolation",
	"color-interpolation-filters",
	"transform",
	"transform-origin",
	"transform-box",
	"d",
	"x",
	"y",
	"cx",
	"cy",
	"r",
	"rx",
	"ry",
	"width",
	"height",
	)

	ALL_STYLES = ("*",)

	# Style changes between sampled frames may be missed; 0 reads all properties per frame.
	STYLE_SAMPLE_FRAMES = 10

	FACT_COLUMNS = (
	"ctm",
	"own",
	"bbox",
	"length",
	"ends",
	"contour",
	"stroke_width",
	"visible_fraction",
	"clip_box",
	"mask_box",
	"resource_inputs",
	"tag",
	"parent",
	"order",
	)

	COLUMN_DOC = {
	"ctm": "where the element sits, as six numbers, in the root SVG's own user space",
	"own": "its own transform alone, without its ancestors' -- `ctm` composes the whole chain",
	"bbox": "its own extent (x, y, w, h) in its own coordinates",
	"length": "the outline length of a shape that has one, and `None` for a shape that has none",
	"ends": "where its outline begins and ends, for telling a draw-on from a move",
	"contour": "32 samples along its outline, already placed in root space",
	"stroke_width": "its painted stroke width in root space; exact under uniform scale",
	"visible_fraction": "the sampled painted fraction kept by supported clips and binary alpha masks",
	"clip_box": "the box a clip leaves visible, already placed in root space",
	"mask_box": "the box a mask's content covers, already placed in root space. Its shape, not its paint",
	"resource_inputs": (
	"referenced SVG definition inputs, keyed by URL/href; each has tag, attrs, effective style and children, "
	"with linked definitions in the same map. Missing/external references are None; no references is {}. "
	"Read with get_column(matrix, path, 'resource_inputs'); group-owned effects stay on the parent row. "
	"These are source inputs, not resolved instance geometry or final visible paint; a difference need not change pixels"
	),
	"tag": "what it is: `path`, `g`, `rect`",
	"parent": "the path of the element that contains it",
	"order": "where it falls among its siblings in the document",
	}


	def _observer_source() -> str:
	with open(_OBSERVER, encoding="utf-8") as f:
	return f.read()


	def _render(page, svg: str) -> None:
	page.set_content(f"<!doctype html><html><body style='margin:0'>{svg}</body></html>", wait_until="load")


	def _observe(page, js: str, styles, baseline, reuse_outline: bool = True, resource_styles=None):
	"""Observe one frame, restoring the style baseline after a cleared browser context."""
	opts = {
	"wantDiff": baseline is not None,
	"styles": styles,
	"resourceStyles": resource_styles,
	"reuseOutline": reuse_outline,
	}
	got = page.evaluate(js, opts)
	if got.get("needsBaseline"):
	page.evaluate("(b) => { window.__baseline = b; }", baseline)
	got = page.evaluate(js, {**opts, "wantDiff": True})
	assert "error" not in got, got["error"]
	return got


	def _spread(total: int, n: int) -> List[int]:
	"""Select evenly spaced frame indices, including endpoints when n permits."""
	if n <= 0 or n >= total:
	return list(range(total))
	if n == 1:
	return [0]
	return sorted({round(i * (total - 1) / (n - 1)) for i in range(n)})


	def _resource_nodes(resources):
	"""Referenced nodes keyed by reference and child position, independently of their drawable owners."""
	for reference, node in resources.items():
	if node is not None:
	yield (reference,), node
	for path, child in _resource_nodes(dict(enumerate(node["children"]))):
	yield (reference, *path), child


	def _moving_styles(page, js: str, frames: List[str], sampled: Sequence[int]) -> tuple[set, set]:
	"""Find styles that vary across sampled frames; unsampled changes may be missed."""
	moved: set = set()
	resource_moved: set = set()
	resource_baseline: dict = {}
	baseline: Dict[str, Dict[str, str]] \| None = None
	born: Dict[str, Dict[str, str]] = {}
	for i in sampled:
	_render(page, frames[i])
	got = _observe(page, js, None, baseline)
	rows = {r["path"]: r for r in got["rows"]}
	resources = {ref: node for row in rows.values() for ref, node in row["resource_inputs"].items()}
	for path, node in _resource_nodes(resources):
	style = node["style"]
	base = resource_baseline.setdefault(path, style)
	resource_moved.update(k for k in base.keys() \| style.keys() if base.get(k) != style.get(k))
	if baseline is None:
	baseline = {path: r["style"] for path, r in rows.items()}
	page.evaluate("(b) => { window.__baseline = b; }", baseline)
	continue
	for path, row in rows.items():
	style = row["style"]
	if path in baseline:
	moved.update(style)
	elif path in born:
	moved.update(k for k, v in style.items() if born[path].get(k) != v)
	else:
	born[path] = style
	return moved, resource_moved


	def _measure_in_process(
	frames: List[str],
	viewport: int = 1000,
	fps: float \| None = None,
	style_floor: Sequence[str] = STYLE_FLOOR,
	frame_indices: Sequence[int] \| None = None,
	style_sample_frames: int = STYLE_SAMPLE_FRAMES,
	reuse_outline: bool = True,
	) -> Dict[str, Any]:
	"""Browser measurement worker; use measure to avoid conflicts with an existing event loop."""
	from playwright.sync_api import sync_playwright

	js = _observer_source()
	per_frame: List[Dict[str, Any]] = []
	canvases: List[Any] = []
	with sync_playwright() as p:
	browser = p.chromium.launch(args=["--disable-dev-shm-usage"])
	version = browser.version
	page = browser.new_page(viewport={"width": viewport, "height": viewport})

	styles: Optional[List[str]] = None
	resource_styles: Optional[List[str]] = None
	if tuple(style_floor) != ALL_STYLES and style_sample_frames > 0 and len(frames) > 1:
	sampled = _spread(len(frames), style_sample_frames)
	moved, resource_moved = _moving_styles(page, js, frames, sampled)
	styles = sorted(set(style_floor) \| moved)
	resource_styles = sorted(set(RESOURCE_STYLE_FLOOR) \| set(style_floor) \| resource_moved)
	page.evaluate("() => { window.__baseline = undefined; }")

	baseline: Dict[str, Dict[str, str]] \| None = None
	for svg in frames:
	_render(page, svg)
	got = _observe(page, js, styles, baseline, reuse_outline, resource_styles)
	rows = {r["path"]: r for r in got["rows"]}
	if baseline is None:
	baseline = {path: r["style"] for path, r in rows.items()}
	page.evaluate("(b) => { window.__baseline = b; }", baseline)
	per_frame.append(rows)
	canvases.append(got["canvas"])
	browser.close()

	return _assemble(per_frame, canvases, version, baseline or {}, fps, style_floor, frame_indices, styles)


	def measure(
	frames: List[str],
	viewport: int = 1000,
	fps: float \| None = None,
	style_floor: Sequence[str] = STYLE_FLOOR,
	frame_indices: Optional[Sequence[int]] = None,
	timeout: float = 900.0,
	style_sample_frames: int = STYLE_SAMPLE_FRAMES,
	reuse_outline: bool = True,
	) -> Dict[str, Any]:
	"""Measure frames in a child process. Coordinates use root SVG units; fps and frame_indices record caller-supplied timing."""
	if not frames:
	raise ValueError("no frames to measure: an animation matrix needs at least one frame")
	with tempfile.TemporaryDirectory() as tmp:
	given, produced = os.path.join(tmp, "given.json"), os.path.join(tmp, "matrix.json")
	with open(given, "w") as f:
	json.dump(
	{
	"frames": list(frames),
	"viewport": viewport,
	"fps": fps,
	"style_floor": list(style_floor),
	"frame_indices": list(frame_indices) if frame_indices is not None else None,
	"style_sample_frames": style_sample_frames,
	"reuse_outline": reuse_outline,
	},
	f,
	)
	try:
	proc = subprocess.run(
	[sys.executable, _SELF, given, produced],
	capture_output=True,
	text=True,
	timeout=timeout,
	)
	except subprocess.TimeoutExpired:
	raise RuntimeError(f"measuring {len(frames)} frames timed out after {timeout:.0f}s") from None
	if not os.path.exists(produced):
	raise RuntimeError(f"measuring failed (exit {proc.returncode}): {(proc.stderr or '')[-1500:]}")
	with open(produced) as f:
	return json.load(f)


	def _assemble(
	per_frame,
	canvases,
	version: str,
	baseline,
	fps: float \| None = None,
	style_floor: Sequence[str] = STYLE_FLOOR,
	frame_indices: Sequence[int] \| None = None,
	styles_measured: Sequence[str] \| None = None,
	) -> Dict[str, Any]:
	"""Split observations into constant and per-frame columns; absent nodes contribute None."""
	n = len(per_frame)
	if frame_indices is None:
	frame_indices = list(range(n))
	elif len(frame_indices) != n:
	raise ValueError(f"{len(frame_indices)} frame indices for {n} frames: they name the frames measured")
	paths: List[str] = []
	for rows in per_frame:
	for path in rows:
	if path not in paths:
	paths.append(path)

	if tuple(style_floor) != ALL_STYLES:
	resource_seen: dict = {}
	for rows in per_frame:
	for row in rows.values():
	for resource_path, node in _resource_nodes(row.get("resource_inputs", {})):
	resource_seen.setdefault(resource_path, []).append(node)
	kept: dict = {}
	for nodes in resource_seen.values():
	base = nodes[0]["style"]
	keep = set(RESOURCE_STYLE_FLOOR) \| set(style_floor)
	keep.update(
	k for node in nodes for k in base.keys() \| node["style"].keys() if base.get(k) != node["style"].get(k)
	)
	for node in nodes:
	kept.setdefault(id(node), (node, set()))[1].update(keep)
	# Shared definitions must be discovered before their styles are pruned.
	for node, keep in kept.values():
	node["style"] = {k: v for k, v in node["style"].items() if k in keep}

	objects: Dict[str, Any] = {}
	for path in paths:
	seen = [rows.get(path) for rows in per_frame]
	cells: Dict[str, List[Any]] = {}
	for key in FACT_COLUMNS:
	cells[key] = [None if r is None else r.get(key) for r in seen]

	attr_names = sorted({k for r in seen if r for k in r["attrs"]})
	for name in attr_names:
	cells[f"attr.{name}"] = [None if r is None else r["attrs"].get(name) for r in seen]

	# Missing style entries reuse the frame-zero baseline.
	base = baseline.get(path, {})
	style_names = set(base) \| {k for r in seen if r for k in r["style"]}
	for name in sorted(style_names):
	cells[f"style.{name}"] = [None if r is None else r["style"].get(name, base.get(name)) for r in seen]

	const, series = {}, {}
	for key, values in cells.items():
	present = [v for v in values if v is not None]
	if present and all(v == present[0] for v in present) and len(present) == n:
	const[key] = present[0]
	elif present:
	series[key] = values
	else:
	const[key] = None
	if tuple(style_floor) != ALL_STYLES:
	const = {k: v for k, v in const.items() if not k.startswith("style.") or k[len("style.") :] in style_floor}
	objects[path] = {"const": const, "series": series}

	canvas_const = all(c == canvases[0] for c in canvases)
	return {
	"info": {
	"frames": n,
	"fps": fps,
	# Duration spans the intervals between frames, not the number of samples.
	"duration": round((n - 1) / fps, 6) if fps else None,
	"chromium": version,
	"source_frames": list(frame_indices),
	"canvas": canvases[0] if canvas_const else None,
	"canvas_series": None if canvas_const else canvases,
	"aliased_rows": _aliased_rows(objects),
	# None means every style property was measured.
	"styles_measured": list(styles_measured) if styles_measured is not None else None,
	},
	"objects": objects,
	}


	def _aliased_rows(objects: Dict[str, Any]) -> List[str]:
	"""Paths with uncertain identity after sibling changes, including affected descendants."""
	aliases = set()
	siblings: Dict[str, List[str]] = {}
	identifiers = {}
	anonymous = set()
	for path, obj in objects.items():
	for column in ("tag", "attr.id"):
	if len({v for v in obj["series"].get(column, []) if v}) > 1:
	aliases.add(path)
	tags = obj["series"].get("tag", [])
	ids = obj["series"].get("attr.id", [obj["const"].get("attr.id")] * max(1, len(tags)))
	identifiers[path] = {v for v in ids if v}
	tags = tags or [obj["const"].get("tag")] * len(ids)
	if any(not identity and tag is not None for identity, tag in zip(ids, tags)):
	anonymous.add(path)
	siblings.setdefault(path.rsplit("[", 1)[0], []).append(path)

	for paths in siblings.values():
	if len(paths) < 2 or not any(None in objects[p]["series"].get("tag", []) for p in paths):
	continue
	for path in paths:
	tags = objects[path]["series"].get("tag", [])
	if tags and sum(t is not None for t in tags) < 2:
	continue
	if path in anonymous or any(identifiers[path] & identifiers[p] for p in paths if p != path):
	aliases.add(path)

	# ponytail: Equal-count anonymous replacements cannot be identified from these observations; stable IDs are needed for that.
	return [p for p in objects if p in aliases or any(p.startswith(a + "/") for a in aliases)]


	if __name__ == "__main__":
	with open(sys.argv[1]) as f:
	asked = json.load(f)
	matrix = _measure_in_process(
	asked["frames"],
	viewport=asked["viewport"],
	fps=asked["fps"],
	style_floor=asked["style_floor"],
	frame_indices=asked["frame_indices"],
	style_sample_frames=asked.get("style_sample_frames", STYLE_SAMPLE_FRAMES),
	reuse_outline=asked.get("reuse_outline", True),
	)
	with open(sys.argv[2], "w") as f:
	json.dump(matrix, f)