From 4ecd38d7dd9239cbe64290d88d95c2920b140f3b Mon Sep 17 00:00:00 2001
From: Kimoon Han <khan@kaist.ac.kr>
Date: Tue, 19 Nov 2024 14:59:30 +0900
Subject: [PATCH] perf(plotting): improve module import time

Accelerates initial import time by refactoring heavy imports to reside inside functions. Furthermore, automatically importing cmocean, cmasher, and colorcet packages are now disabled. The user must import them manually to access those colormaps.
---
 src/erlab/plotting/__init__.py    | 9 ---------
 src/erlab/plotting/annotations.py | 6 ++++--
 src/erlab/plotting/bz.py          | 3 ++-
 src/erlab/plotting/colors.py      | 3 +--
 4 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/src/erlab/plotting/__init__.py b/src/erlab/plotting/__init__.py
index 0de6570c..a79ddaa6 100644
--- a/src/erlab/plotting/__init__.py
+++ b/src/erlab/plotting/__init__.py
@@ -19,7 +19,6 @@
 
 """
 
-import importlib
 import io
 import os
 import pkgutil
@@ -30,14 +29,6 @@
 import matplotlib.style
 import numpy as np
 
-# Import colormaps if available
-if importlib.util.find_spec("cmasher"):
-    importlib.import_module("cmasher")
-if importlib.util.find_spec("cmocean"):
-    importlib.import_module("cmocean")
-if importlib.util.find_spec("colorcet"):
-    importlib.import_module("colorcet")
-
 
 def load_igor_ct(
     file: str | os.PathLike | io.BytesIO, name: str, register_reversed: bool = True
diff --git a/src/erlab/plotting/annotations.py b/src/erlab/plotting/annotations.py
index 64635de1..e67988f0 100644
--- a/src/erlab/plotting/annotations.py
+++ b/src/erlab/plotting/annotations.py
@@ -28,8 +28,6 @@
 from typing import TYPE_CHECKING, Any, Literal, cast
 
 import matplotlib
-import matplotlib.backends.backend_pdf
-import matplotlib.backends.backend_svg
 import matplotlib.figure
 import matplotlib.font_manager
 import matplotlib.mathtext
@@ -286,8 +284,12 @@ def copy_mathtext(
     fig.text(0, depth / height, s, fontproperties=fontproperties)
 
     if svg:
+        import matplotlib.backends.backend_svg
+
         matplotlib.backends.backend_svg.FigureCanvasSVG(fig)
     else:
+        import matplotlib.backends.backend_pdf
+
         matplotlib.backends.backend_pdf.FigureCanvasPdf(fig)
 
     for k, v in mathtext_rc.items():
diff --git a/src/erlab/plotting/bz.py b/src/erlab/plotting/bz.py
index 38463c19..91a00ea9 100644
--- a/src/erlab/plotting/bz.py
+++ b/src/erlab/plotting/bz.py
@@ -8,7 +8,6 @@
 import matplotlib.pyplot as plt
 import numpy as np
 import numpy.typing as npt
-import scipy.spatial
 from matplotlib.patches import RegularPolygon
 
 from erlab.plotting.colors import axes_textcolor
@@ -70,6 +69,8 @@ def get_bz_edge(
     # Get index of origin
     zero_ind = np.where((points == 0).all(axis=1))[0][0]
 
+    import scipy.spatial
+
     vor = scipy.spatial.Voronoi(points)
 
     lines = []
diff --git a/src/erlab/plotting/colors.py b/src/erlab/plotting/colors.py
index c3a0182f..72d1723e 100644
--- a/src/erlab/plotting/colors.py
+++ b/src/erlab/plotting/colors.py
@@ -7,8 +7,7 @@
 <https://matplotlib.org/stable/tutorials/colors/colormaps.html>`_ colormaps, `cmasher
 <https://cmasher.readthedocs.io>`_, `cmocean <https://matplotlib.org/cmocean/>`_, and
 `colorcet <https://colorcet.holoviz.org>`_ packages can be installed to extend the
-available colormaps. If these packages are installed, they will be automatically
-imported upon importing `erlab.plotting`.
+available colormaps.
 
 Colormap Normalization
 ----------------------