add basic latex display support if unicodeit is installed (#858)

If the external package
[unicodeit](https://github.com/svenkreiss/unicodeit) is installed,
translate variable names which contain simple LaTeX into unicode that
mimics the correct LaTeX rendering. This only works for very basic LaTeX
like `$\alpha$`.

Makefile

@@ -20,11 +20,11 @@ cov: build/done build/testdep
 	JUPYTER_PLATFORM_DIRS=1 coverage run -m pytest
 	python -m pip uninstall --yes numba ipykernel ipywidgets
 	coverage run --append -m pytest
-	python -m pip uninstall --yes scipy matplotlib
+	python -m pip uninstall --yes scipy matplotlib unicodeit
 	coverage run --append -m pytest
-	pip install numba ipykernel ipywidgets scipy matplotlib
 	coverage html -d htmlcov
 	coverage report -m
+	python .ci/install_deps.py test
 	@echo htmlcov/index.html
 
 doc: build/done build/html/done

pyproject.toml

@@ -49,19 +49,23 @@ documentation = "https://iminuit.readthedocs.io"
 test = [
     "coverage",
     "cython",
-    "ipywidgets",
+    # ipywidgets 8.0.5 and 8.0.6 are broken
+    # see https://github.com/jupyter-widgets/ipywidgets/issues/3731
+    "ipywidgets<8.0.5",
     "ipykernel",  # needed by ipywidgets 8.0.6
     "joblib",
     "jacobi",
     "matplotlib",
+    # numba currently requires numpy<1.24
     "numpy<1.24",
     "numba",
     "numba-stats",
     "pytest",
     "scipy",
     "tabulate",
     "boost_histogram",
-    "resample>=1.5"
+    "resample",
+    "unicodeit"
 ]
 doc = [
     "sphinx~=5.3.0",

src/iminuit/_optional_dependencies.py

@@ -0,0 +1,18 @@
+import contextlib
+import warnings
+from iminuit.warnings import OptionalDependencyWarning
+
+
+@contextlib.contextmanager
+def optional_module_for(functionality, *, replace=None, stacklevel=3):
+    try:
+        yield
+    except ModuleNotFoundError as e:
+        package = e.name.split(".")[0]
+        if replace:
+            package = replace.get(package, package)
+        msg = (
+            f"{functionality} requires optional package {package!r}. "
+            f"Install {package!r} manually to enable this functionality."
+        )
+        warnings.warn(msg, OptionalDependencyWarning, stacklevel=stacklevel)

src/iminuit/_repr_html.py

@@ -1,4 +1,4 @@
-from ._repr_text import pdg_format, matrix_format, fmin_fields
+from ._repr_text import pdg_format, matrix_format, fmin_fields, _parse_latex
 
 good_style = "background-color:#92CCA6;color:black"
 bad_style = "background-color:#c15ef7;color:black"
@@ -201,7 +201,7 @@ def params(mps):
         rows.append(
             tr(
                 th(str(i)),
-                td(mp.name),
+                td(_parse_latex(mp.name)),
                 td(v),
                 td(e),
                 td(mem),
@@ -243,7 +243,7 @@ def merrors(mes):
     for me in mes:
         header.append(
             th(
-                me.name,
+                _parse_latex(me.name),
                 colspan=2,
                 title="Parameter name",
                 style="text-align:center",
@@ -279,7 +279,7 @@ def merrors(mes):
 
 
 def matrix(arr):
-    names = tuple(arr._var2pos)
+    names = [_parse_latex(x) for x in arr._var2pos]
 
     n = len(names)
 
@@ -316,3 +316,29 @@ def matrix(arr):
         rows.append(tr(*cols))
 
     return to_str(table(tr(td(), *[th(v) for v in names]), *rows))
+
+
+# def _parse_latex(s):
+#     if s.startswith("$") and s.endswith("$"):
+#         with optional_module_for("displaying LaTeX"):
+#             from matplotlib.backends.backend_svg import RendererSVG
+#             from matplotlib.font_manager import FontProperties
+#             from io import StringIO
+
+#             fp = FontProperties(size=9)
+#             # get bounding box of rendered text
+#             r = RendererSVG(0, 0, StringIO())
+#             w, h, _ = r.get_text_width_height_descent(s, fp, ismath=True)
+
+#             with StringIO() as f:
+#                 # render LaTeX as path
+#                 r = RendererSVG(w, h, f)
+#                 r.draw_text(r.new_gc(), 0, h, s, fp, angle=0, ismath=True)
+#                 f.seek(0)
+#                 svg = f.read()
+
+#             # strip preamble
+#             svg = svg[svg.index("<svg") + 4 :]
+#             return f'<svg role="img" style="fill:#f0f0f0" {svg}'
+
+#     return s

src/iminuit/_repr_text.py

@@ -1,4 +1,5 @@
 from .pdg_format import _round, _strip
+from iminuit._optional_dependencies import optional_module_for
 import re
 import numpy as np
 
@@ -90,7 +91,8 @@ def fmin(fm):
 
 
 def params(mps):
-    vnames = (mp.name for mp in mps)
+    vnames = [_parse_latex(mp.name) for mp in mps]
+
     name_width = max([4] + [len(x) for x in vnames])
     num_width = max(2, len(f"{len(mps) - 1}"))
 
@@ -123,7 +125,7 @@ def params(mps):
             format_row(
                 ws,
                 str(i),
-                mp.name,
+                vnames[i],
                 val,
                 err,
                 mel,
@@ -143,7 +145,7 @@ def merrors(mes):
     n = len(mes)
     ws = [10] + [23] * n
     l1 = format_line(ws, "┌" + "┬" * n + "┐")
-    header = format_row(ws, "", *(m.name for m in mes))
+    header = format_row(ws, "", *(_parse_latex(m.name) for m in mes))
     ws = [10] + [11] * (2 * n)
     l2 = format_line(ws, "├" + "┼┬" * n + "┤")
     l3 = format_line(ws, "└" + "┴" * n * 2 + "┘")
@@ -177,7 +179,7 @@ def merrors(mes):
 
 
 def matrix(arr):
-    names = tuple(arr._var2pos)
+    names = [_parse_latex(x) for x in arr._var2pos]
 
     n = len(arr)
     nums = matrix_format(arr)
@@ -219,3 +221,12 @@ def matrix_format(matrix):
                 x = pdg_format(matrix[i, j], matrix[i, i], matrix[j, j])[0]
                 r.append(x)
     return r
+
+
+def _parse_latex(s):
+    if s.startswith("$") and s.endswith("$"):
+        with optional_module_for("rendering simple LaTeX"):
+            import unicodeit
+
+            return unicodeit.replace(s[1:-1])
+    return s

src/iminuit/minuit.py

@@ -18,6 +18,7 @@
 import numpy as np
 import typing as _tp
 from iminuit.typing import UserBound
+from iminuit._optional_dependencies import optional_module_for
 
 # Better use numpy.typing.ArrayLike in the future, but this
 # requires dropping Python-3.6 support
@@ -1898,18 +1899,12 @@ def mncontour(
         pts = np.append(pts, pts[:1], axis=0)
 
         if interpolated > size:
-            try:
+            with optional_module_for("interpolation"):
                 from scipy.interpolate import CubicSpline
 
                 xg = np.linspace(0, 1, len(pts))
                 spl = CubicSpline(xg, pts, bc_type="periodic")
                 pts = spl(np.linspace(0, 1, interpolated))
-
-            except ModuleNotFoundError:
-                warnings.warn(
-                    "Interpolation requires scipy. Please install scipy.",
-                    mutil.IMinuitWarning,
-                )
         return pts
 
     def draw_mncontour(

src/iminuit/util.py

@@ -9,6 +9,7 @@
 from argparse import Namespace
 from iminuit import _repr_html, _repr_text, _deprecated
 from iminuit.typing import Key, UserBound
+from iminuit.warnings import IMinuitWarning, HesseFailedWarning, PerformanceWarning
 import numpy as np
 from numpy.typing import NDArray
 from typing import (
@@ -54,18 +55,6 @@
 )
 
 
-class IMinuitWarning(RuntimeWarning):
-    """Generic iminuit warning."""
-
-
-class HesseFailedWarning(IMinuitWarning):
-    """HESSE failed warning."""
-
-
-class PerformanceWarning(UserWarning):
-    """Warning about performance issues."""
-
-
 class BasicView(abc.ABC):
     """
     Array-like view of parameter state.

src/iminuit/warnings.py

@@ -0,0 +1,17 @@
+"""Warnings used by iminuit."""
+
+
+class IMinuitWarning(RuntimeWarning):
+    """Generic iminuit warning."""
+
+
+class OptionalDependencyWarning(IMinuitWarning):
+    """Feature requires an optional external package."""
+
+
+class HesseFailedWarning(IMinuitWarning):
+    """HESSE failed warning."""
+
+
+class PerformanceWarning(UserWarning):
+    """Warning about performance issues."""

tests/params_latex_1.txt

@@ -0,0 +1,5 @@
+┌───┬──────┬───────────┬───────────┬────────────┬────────────┬─────────┬─────────┬───────┐
+│   │ Name │   Value   │ Hesse Err │ Minos Err- │ Minos Err+ │ Limit-  │ Limit+  │ Fixed │
+├───┼──────┼───────────┼───────────┼────────────┼────────────┼─────────┼─────────┼───────┤
+│ 0 │ α    │   1.00    │   0.01    │            │            │         │         │       │
+└───┴──────┴───────────┴───────────┴────────────┴────────────┴─────────┴─────────┴───────┘

tests/params_latex_2.txt

@@ -0,0 +1,5 @@
+┌───┬──────────┬───────────┬───────────┬────────────┬────────────┬─────────┬─────────┬───────┐
+│   │ Name     │   Value   │ Hesse Err │ Minos Err- │ Minos Err+ │ Limit-  │ Limit+  │ Fixed │
+├───┼──────────┼───────────┼───────────┼────────────┼────────────┼─────────┼─────────┼───────┤
+│ 0 │ $\alpha$ │   1.00    │   0.01    │            │            │         │         │       │
+└───┴──────────┴───────────┴───────────┴────────────┴────────────┴─────────┴─────────┴───────┘

tests/test_minuit.py

@@ -3,7 +3,8 @@
 import numpy as np
 from numpy.testing import assert_allclose, assert_equal
 from iminuit import Minuit
-from iminuit.util import Param, IMinuitWarning, make_func_code
+from iminuit.util import Param, make_func_code
+from iminuit.warnings import IMinuitWarning, OptionalDependencyWarning
 from iminuit.typing import Annotated
 from pytest import approx
 from argparse import Namespace
@@ -185,7 +186,10 @@ def test_mncontour_interpolated():
     assert len(pts) == 21
 
     if not scipy_available:
-        with pytest.warns(IMinuitWarning, match="Interpolation requires scipy"):
+        with pytest.warns(
+            OptionalDependencyWarning,
+            match="interpolation requires optional package 'scipy'",
+        ):
             pts = m.mncontour("x", "y", size=20, interpolated=200)
             assert len(pts) == 21
     else:

tests/test_repr.py

@@ -244,6 +244,24 @@ def test_text_params(minuit):
     assert _repr_text.params(minuit.params) == ref("params.txt")
 
 
+def test_text_params_with_latex_names():
+    m = Minuit(lambda x: x**2, 1, name=[r"$\alpha$"])
+
+    try:
+        import unicodeit  # noqa
+
+        assert _repr_text.params(m.params) == ref("params_latex_1.txt")
+
+    except ModuleNotFoundError:
+        from iminuit.warnings import OptionalDependencyWarning
+
+        with pytest.warns(
+            OptionalDependencyWarning,
+            match="rendering simple LaTeX requires optional package 'unicodeit'",
+        ):
+            assert _repr_text.params(m.params) == ref("params_latex_2.txt")
+
+
 def test_text_params_with_long_names():
     mps = [
         Param(

tests/test_util.py

@@ -4,6 +4,7 @@
 from numpy.testing import assert_equal, assert_allclose
 import numpy as np
 from iminuit._core import MnUserParameterState
+from iminuit._optional_dependencies import optional_module_for
 import pickle
 
 
@@ -784,3 +785,28 @@ def test_smart_sampling_1(fn_expected):
 def test_smart_sampling_2():
     with pytest.warns(RuntimeWarning):
         util._smart_sampling(np.log, 1e-10, 1, tol=1e-10)
+
+
+def test_optional_module_for_1():
+    with optional_module_for("foo"):
+        import iminuit  # noqa
+
+
+def test_optional_module_for_2():
+    from iminuit.warnings import OptionalDependencyWarning
+
+    with pytest.warns(
+        OptionalDependencyWarning, match="foo requires optional package 'foobarbaz'"
+    ):
+        with optional_module_for("foo"):
+            import foobarbaz  # noqa
+
+
+def test_optional_module_for_3():
+    from iminuit.warnings import OptionalDependencyWarning
+
+    with pytest.warns(
+        OptionalDependencyWarning, match="foo requires optional package 'foo'"
+    ):
+        with optional_module_for("foo", replace={"foobarbaz": "foo"}):
+            import foobarbaz  # noqa