Custom stylesheets

docs/user_guide.rst

@@ -36,3 +36,14 @@ To use these:
 1. Open the desired widget using the ``Plugins > napari-matplotlib`` menu in napari.
 2. Select a single layer that has a features table using the napari layers list in the bottom left-hand side of the window.
 3. Use the drop down menu(s) under the Matplotlib figure to select the feature(s) to plot.
+
+Customising plots
+-----------------
+`Matplotlib style sheets <https://matplotlib.org/stable/tutorials/introductory/customizing.html#defining-your-own-style>`__ can be used to customise
+the plots generated by ``napari-matplotlib``.
+To use a custom style sheet:
+
+1. Save it as ``napari-matplotlib.mplstyle``
+2. Put it in the Matplotlib configuration directory.
+   The location of this directory varies on different computers,
+   and can be found by calling :func:`matplotlib.get_configdir()`.

src/napari_matplotlib/base.py

@@ -2,6 +2,7 @@
 from pathlib import Path
 from typing import List, Optional, Tuple
 
+import matplotlib
 import matplotlib.style as mplstyle
 import napari
 from matplotlib.backends.backend_qtagg import (
@@ -16,6 +17,10 @@
 
 __all__ = ["BaseNapariMPLWidget", "NapariMPLWidget", "SingleAxesWidget"]
 
+_CUSTOM_STYLE_PATH = (
+    Path(matplotlib.get_configdir()) / "napari-matplotlib.mplstyle"
+)
+
 
 class BaseNapariMPLWidget(QWidget):
     """
@@ -46,7 +51,6 @@ def __init__(
         with mplstyle.context(self.mpl_style_sheet_path):
             self.canvas = FigureCanvas()
 
-        self.canvas.figure.patch.set_facecolor("none")
         self.canvas.figure.set_layout_engine("constrained")
         self.toolbar = NapariNavigationToolbar(
             self.canvas, parent=self
@@ -73,6 +77,8 @@ def mpl_style_sheet_path(self) -> Path:
         """
         if self._mpl_style_sheet_path is not None:
             return self._mpl_style_sheet_path
+        elif (_CUSTOM_STYLE_PATH).exists():
+            return _CUSTOM_STYLE_PATH
         elif self._napari_theme_has_light_bg():
             return Path(__file__).parent / "styles" / "light.mplstyle"
         else:

src/napari_matplotlib/tests/test_theme.py

@@ -1,10 +1,15 @@
+import os
+import shutil
 from copy import deepcopy
+from pathlib import Path
 
+import matplotlib
 import napari
 import numpy as np
 import pytest
+from matplotlib.colors import to_rgba
 
-from napari_matplotlib import ScatterWidget
+from napari_matplotlib import HistogramWidget, ScatterWidget
 from napari_matplotlib.base import NapariMPLWidget
 
 
@@ -140,3 +145,46 @@ def test_custom_theme(make_napari_viewer, theme_path, brain_data):
     viewer.layers.selection.add(viewer.layers[1])
 
     return deepcopy(widget.figure)
+
+
+def find_mpl_stylesheet(name: str) -> Path:
+    """Find the built-in matplotlib stylesheet."""
+    return Path(matplotlib.__path__[0]) / f"mpl-data/stylelib/{name}.mplstyle"
+
+
+def test_custom_stylesheet(make_napari_viewer, image_data):
+    """
+    Test that a stylesheet in the current directory is given precidence.
+
+    Do this by copying over a stylesheet from matplotlib's built in styles,
+    naming it correctly, and checking the colours are as expected.
+    """
+    # Copy Solarize_Light2 as if it was a user-overriden stylesheet.
+    style_sheet_path = (
+        Path(matplotlib.get_configdir()) / "napari-matplotlib.mplstyle"
+    )
+    if style_sheet_path.exists():
+        pytest.skip("Won't ovewrite existing custom style sheet.")
+    shutil.copy(
+        find_mpl_stylesheet("Solarize_Light2"),
+        style_sheet_path,
+    )
+
+    try:
+        viewer = make_napari_viewer()
+        viewer.add_image(image_data[0], **image_data[1])
+        widget = HistogramWidget(viewer)
+        assert widget.mpl_style_sheet_path == style_sheet_path
+        ax = widget.figure.gca()
+
+        # The axes should have a light brownish grey background:
+        assert ax.get_facecolor() == to_rgba("#eee8d5")
+        assert ax.patch.get_facecolor() == to_rgba("#eee8d5")
+
+        # The figure background and axis gridlines are light yellow:
+        assert widget.figure.patch.get_facecolor() == to_rgba("#fdf6e3")
+        for gridline in ax.get_xgridlines() + ax.get_ygridlines():
+            assert gridline.get_visible() is True
+            assert gridline.get_color() == "#fdf6e3"
+    finally:
+        os.remove(style_sheet_path)