Add generated score SVG fallback

apps/theme_lab/app.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import argparse
+from html import escape
 import os
 import pickle
 import random
@@ -46,7 +47,7 @@ MARKOV_CACHE_DIR = ROOT / "models" / "theme_lab_markov_cache"
 DEFAULT_MARKOV_CACHE = MARKOV_CACHE_DIR / "default.pkl"
 MARKOV_CACHE_FORMAT_VERSION = 1
 MARKOV_PRECOMPUTED_WARM_SAMPLES = 4
-SCORE_PREVIEW_RENDER_VERSION = "strip-ties-beams-v1"
+SCORE_PREVIEW_RENDER_VERSION = "strip-ties-beams-simple-svg-v2"
 GENERATED_ROOT.mkdir(parents=True, exist_ok=True)
 CATALOG_SCORE_ROOT.mkdir(parents=True, exist_ok=True)
 
@@ -371,6 +372,95 @@ def sequence_note_events(sequence: tuple[Symbol, ...], key_name: str) -> list[di
     return events
 
 
+def write_simple_score_svg(notes: list[dict[str, object]], svg_path: Path, title: str) -> Path | None:
+    if not notes:
+        return None
+
+    total_beats = max(float(note["start_beat"]) + float(note["duration_beats"]) for note in notes)
+    width = max(980, int(160 + total_beats * 58))
+    height = 260
+    left = 72
+    right = 42
+    staff_top = 92
+    line_gap = 12
+    staff_bottom = staff_top + line_gap * 4
+    pitch_step = 3.5
+    x_scale = (width - left - right) / max(total_beats, 1.0)
+
+    def note_x(note: dict[str, object]) -> float:
+        return left + float(note["start_beat"]) * x_scale
+
+    def note_y(pitch: int) -> float:
+        return staff_bottom - (pitch - 64) * pitch_step
+
+    def duration_to_fill(duration: float) -> str:
+        return "#fff" if duration >= 2.0 else "#000"
+
+    def duration_to_stem(duration: float) -> bool:
+        return duration < 4.0
+
+    elements = [
+        f'<svg xmlns="http://www.w3.org/2000/svg" width="{width}" height="{height}" viewBox="0 0 {width} {height}">',
+        '<rect width="100%" height="100%" fill="#fff"/>',
+        f'<text x="{width / 2:.1f}" y="42" text-anchor="middle" font-family="Georgia, serif" font-size="26">{escape(title)}</text>',
+        f'<text x="22" y="{staff_top + 30}" font-family="Georgia, serif" font-size="48">&#119070;</text>',
+        f'<text x="{left - 20}" y="{staff_top + 33}" font-family="Georgia, serif" font-size="27" font-weight="700">4</text>',
+        f'<text x="{left - 20}" y="{staff_top + 58}" font-family="Georgia, serif" font-size="27" font-weight="700">4</text>',
+    ]
+    for line in range(5):
+        y = staff_top + line * line_gap
+        elements.append(f'<line x1="18" x2="{width - 24}" y1="{y}" y2="{y}" stroke="#000" stroke-width="1"/>')
+
+    measure_beat = 4.0
+    bar = measure_beat
+    while bar < total_beats:
+        x = left + bar * x_scale
+        elements.append(f'<line x1="{x:.1f}" x2="{x:.1f}" y1="{staff_top}" y2="{staff_bottom}" stroke="#000" stroke-width="1.3"/>')
+        bar += measure_beat
+
+    for note in notes:
+        pitch = int(note["pitch"])
+        duration = float(note["duration_beats"])
+        x = note_x(note)
+        y = note_y(pitch)
+        while y < staff_top - line_gap:
+            elements.append(
+                f'<line x1="{x - 12:.1f}" x2="{x + 12:.1f}" y1="{y:.1f}" y2="{y:.1f}" stroke="#000" stroke-width="1"/>'
+            )
+            y += line_gap
+        y = note_y(pitch)
+        while y > staff_bottom + line_gap:
+            elements.append(
+                f'<line x1="{x - 12:.1f}" x2="{x + 12:.1f}" y1="{y:.1f}" y2="{y:.1f}" stroke="#000" stroke-width="1"/>'
+            )
+            y -= line_gap
+        y = note_y(pitch)
+        accidental = {1: "#", 3: "#", 6: "#", 8: "#", 10: "#"}.get(pitch % 12)
+        if accidental:
+            elements.append(
+                f'<text x="{x - 22:.1f}" y="{y + 5:.1f}" font-family="Georgia, serif" font-size="18">{accidental}</text>'
+            )
+        elements.append(
+            f'<ellipse cx="{x:.1f}" cy="{y:.1f}" rx="8" ry="5.5" fill="{duration_to_fill(duration)}" stroke="#000" stroke-width="1.6" transform="rotate(-18 {x:.1f} {y:.1f})"/>'
+        )
+        if duration_to_stem(duration):
+            stem_x = x + 7
+            stem_y = y - 42
+            elements.append(f'<line x1="{stem_x:.1f}" x2="{stem_x:.1f}" y1="{y:.1f}" y2="{stem_y:.1f}" stroke="#000" stroke-width="1.6"/>')
+            if duration <= 0.5:
+                elements.append(
+                    f'<path d="M {stem_x:.1f} {stem_y:.1f} q 18 8 6 24" fill="none" stroke="#000" stroke-width="1.5"/>'
+                )
+
+    final_x = left + total_beats * x_scale + 14
+    elements.append(f'<line x1="{final_x:.1f}" x2="{final_x:.1f}" y1="{staff_top}" y2="{staff_bottom}" stroke="#000" stroke-width="1.3"/>')
+    elements.append(f'<line x1="{final_x + 5:.1f}" x2="{final_x + 5:.1f}" y1="{staff_top}" y2="{staff_bottom}" stroke="#000" stroke-width="3"/>')
+    elements.append("</svg>")
+
+    svg_path.write_text("\n".join(elements), encoding="utf-8")
+    return svg_path if svg_path.exists() else None
+
+
 def has_verovio_renderer() -> bool:
     if shutil.which("verovio") is not None:
         return True
@@ -721,14 +811,17 @@ def generate(request: GenerateRequest) -> dict[str, object]:
     for index, sequence in enumerate(generated, start=1):
         stem = f"generated_{index:02d}"
         musicxml_path = output_dir / f"{stem}.musicxml"
+        notes = sequence_note_events(sequence, request.key)
         svg_path = render_musicxml_to_svg(musicxml_path)
+        if svg_path is None:
+            svg_path = write_simple_score_svg(notes, musicxml_path.with_suffix(".svg"), f"{request.engine} sample {index:02d}")
         samples.append(
             {
                 "index": index,
                 "title": f"{request.engine} sample {index:02d}",
                 "relative_pcs": [symbol.rpc for symbol in sequence],
                 "durations": [symbol.duration for symbol in sequence],
-                "notes": sequence_note_events(sequence, request.key),
+                "notes": notes,
                 "midi_url": f"/generated/{run_id}/{stem}.mid",
                 "abc_url": f"/generated/{run_id}/{stem}.abc",
                 "musicxml_url": f"/generated/{run_id}/{stem}.musicxml",