giant/analysis/render.py

@@ -21,6 +21,7 @@ cycle.
 
 from __future__ import annotations
 
+import dataclasses
 import subprocess
 from pathlib import Path
 
@@ -32,6 +33,27 @@ from giant.analysis.reduced import Reduced
 
 _REFERENCE_LABEL = "reference (Geant4)"
 
+_TEX_ESCAPE_MAP = {
+    "\\": r"\textbackslash{}",
+    "%": r"\%",
+    "&": r"\&",
+    "#": r"\#",
+    "$": r"\$",
+    "_": r"\_",
+    "{": r"\{",
+    "}": r"\}",
+}
+
+
+def _tex_escape(text: str) -> str:
+    """Escape characters LaTeX treats specially in catalog-authored title/xlabel
+    text (e.g. a literal ``%`` in a "90% of deposited energy" title, which
+    ``usetex`` otherwise reads as a comment marker and aborts the whole figure —
+    see gitea #81). A single pass over the *original* characters, so the
+    backslashes an escape itself introduces (e.g. ``\textbackslash{}``) are
+    never re-escaped."""
+    return "".join(_TEX_ESCAPE_MAP.get(c, c) for c in text)
+
 
 def _ref_color() -> str:
     return ps.colors.INK["primary"]
@@ -421,8 +443,14 @@ _RENDERERS = {
 
 
 def render(r: Reduced, run_meta: dict | None = None):
-    """Build the matplotlib figure for one reduced artifact (dispatch on kind)."""
-    return _RENDERERS[r.kind](r, _figure_params(run_meta or {}))
+    """Build the matplotlib figure for one reduced artifact (dispatch on kind).
+
+    ``title``/``xlabel`` are LaTeX-escaped here, at the one point every kind's
+    renderer draws them from — ``_plot_metadata`` deliberately keeps using the
+    unescaped ``r`` for the gallery YAML, which isn't LaTeX.
+    """
+    escaped = dataclasses.replace(r, title=_tex_escape(r.title), xlabel=_tex_escape(r.xlabel))
+    return _RENDERERS[r.kind](escaped, _figure_params(run_meta or {}))
 
 
 def _plot_metadata(r: Reduced, run_meta: dict) -> dict:

tests/test_render.py

@@ -461,3 +461,30 @@ def test_plot_metadata_omits_parameters_when_run_meta_empty():
     meta = render_mod._plot_metadata(r, {})
     assert "parameters" not in meta
     assert "note" not in meta
+
+
+def test_tex_escape_handles_percent_and_other_special_chars():
+    assert render_mod._tex_escape("90% of deposited energy") == r"90\% of deposited energy"
+    assert render_mod._tex_escape(r"a_b & c#d $e {f} \bar") == r"a\_b \& c\#d \$e \{f\} \textbackslash{}bar"
+
+
+def test_render_survives_title_and_xlabel_with_literal_percent(tmp_path: Path):
+    # Regression test for gitea #81: a literal "%" in a catalog title (e.g.
+    # "Shower containment depth (90% of deposited energy)") crashed the whole
+    # LaTeX render, since usetex treats an unescaped "%" as a comment marker.
+    reduced = [
+        Reduced(
+            "shower_containment_depth_90",
+            "shower",
+            "single_hist",
+            "Shower containment depth (90% of deposited energy)",
+            "depth containing 90% of deposited energy [mm]",
+            {"edges": [0, 1, 2], "series": {"flow": [5, 1]}},
+        ),
+    ]
+    try:
+        pdfs = _try_render(reduced, tmp_path)
+    except RuntimeError as e:  # LaTeX missing at render time
+        pytest.skip(f"LaTeX rendering unavailable: {e}")
+    assert len(pdfs) == 1
+    assert pdfs[0].exists()