matplotlib · QuLogic · Jul 8, 2025 · Jun 4, 2024 · Jun 5, 2024 · Jun 5, 2024
diff --git a/.github/labeler.yml b/.github/labeler.yml
@@ -1,7 +1,9 @@
 ---
 "CI: Run cibuildwheel":
   - changed-files:
-      - any-glob-to-any-file: ['.github/workflows/cibuildwheel.yml']
+      - any-glob-to-any-file:
+          - '.github/workflows/cibuildwheel.yml'
+          - '.github/workflows/wasm.yml'
 "CI: Run cygwin":
   - changed-files:
       - any-glob-to-any-file: ['.github/workflows/cygwin.yml']

diff --git a/.github/workflows/nightlies.yml b/.github/workflows/nightlies.yml
@@ -31,28 +31,28 @@ jobs:
         run: |
           PROJECT_REPO="matplotlib/matplotlib"
           BRANCH="main"
-          WORKFLOW_NAME="cibuildwheel.yml"
           ARTIFACT_PATTERN="cibw-wheels-*"
 
-          gh run --repo "${PROJECT_REPO}" \
-             list --branch "${BRANCH}" \
-                  --workflow "${WORKFLOW_NAME}" \
-                  --json event,status,conclusion,databaseId > runs.json
-          RUN_ID=$(
-            jq --compact-output \
-              '[
-                .[] |
-                # Filter on "push" events to main (merged PRs) ...
-                select(.event == "push") |
-                # that have completed successfully ...
-                select(.status == "completed" and .conclusion == "success")
-               ] |
-              # and get ID of latest build of wheels.
-              sort_by(.databaseId) | reverse | .[0].databaseId' runs.json
-          )
-          gh run --repo "${PROJECT_REPO}" view "${RUN_ID}"
-          gh run --repo "${PROJECT_REPO}" \
-             download "${RUN_ID}" --pattern "${ARTIFACT_PATTERN}"
+          for WORKFLOW_NAME in cibuildwheel.yml wasm.yml; do
+            gh run --repo "${PROJECT_REPO}" \
+               list --branch "${BRANCH}" \
+                    --workflow "${WORKFLOW_NAME}" \
+                    --json event,status,conclusion,databaseId > runs.json
+            RUN_ID=$(
+              jq --compact-output \
+                '[
+                  .[] |
+                  # Filter on "push" events to main (merged PRs) ...
+                  select(.event == "push") |
+                  # that have completed successfully ...
+                  select(.status == "completed" and .conclusion == "success")
+                 ] |
+                # and get ID of latest build of wheels.
+                sort_by(.databaseId) | reverse | .[0].databaseId' runs.json
+            )
+            gh run --repo "${PROJECT_REPO}" view "${RUN_ID}"
+            gh run --repo "${PROJECT_REPO}" download "${RUN_ID}" --pattern "${ARTIFACT_PATTERN}"
+          done
 
           mkdir dist
           mv ${ARTIFACT_PATTERN}/*.whl dist/

diff --git a/.github/workflows/wasm.yml b/.github/workflows/wasm.yml
@@ -0,0 +1,58 @@
+---
+name: Build wasm wheels
+
+on:
+  # Save CI by only running this on release branches or tags.
+  push:
+    branches:
+      - main
+      - v[0-9]+.[0-9]+.x
+    tags:
+      - v*
+  # Also allow running this action on PRs if requested by applying the
+  # "Run cibuildwheel" label.
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - labeled
+
+permissions:
+  contents: read
+
+jobs:
+  build_wasm:
+    if: >-
+      github.event_name == 'push' ||
+      github.event_name == 'pull_request' && (
+        (
+          github.event.action == 'labeled' &&
+          github.event.label.name == 'CI: Run cibuildwheel'
+        ) ||
+        contains(github.event.pull_request.labels.*.name,
+                 'CI: Run cibuildwheel')
+      )
+    name: Build wasm
+    runs-on: ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683  # v4.2.2
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065  # v5.6.0
+        name: Install Python
+        with:
+          python-version: '3.13'
+
+      - name: Build wheels for wasm
+        uses: pypa/cibuildwheel@faf86a6ed7efa889faf6996aa23820831055001a  # v2.23.3
+        env:
+          CIBW_PLATFORM: "pyodide"
+
+      - uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02  # v4.6.2
+        with:
+          name: cibw-wheels-wasm
+          path: ./wheelhouse/*.whl
+          if-no-files-found: error
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -369,6 +369,8 @@
     @classmethod
     def isAvailable(cls):
         """Return whether a MovieWriter subclass is actually available."""
+        if sys.platform == 'emscripten':
+            return False
         return shutil.which(cls.bin_path()) is not None
 
 

diff --git a/lib/matplotlib/dviread.py b/lib/matplotlib/dviread.py
@@ -1135,7 +1135,7 @@ def find_tex_file(filename):
 
     try:
         lk = _LuatexKpsewhich()
-    except FileNotFoundError:
+    except (FileNotFoundError, OSError):
         lk = None  # Fallback to directly calling kpsewhich, as below.
 
     if lk:
@@ -1155,7 +1155,7 @@ def find_tex_file(filename):
             path = (cbook._check_and_log_subprocess(['kpsewhich', filename],
                                                     _log, **kwargs)
                     .rstrip('\n'))
-        except (FileNotFoundError, RuntimeError):
+        except (FileNotFoundError, OSError, RuntimeError):
             path = None
 
     if path:

diff --git a/lib/matplotlib/font_manager.py b/lib/matplotlib/font_manager.py
@@ -287,6 +287,9 @@
         if sys.platform == 'win32':
             installed_fonts = _get_win32_installed_fonts()
             fontpaths = []
+        elif sys.platform == 'emscripten':
+            installed_fonts = []
+            fontpaths = []
         else:
             installed_fonts = _get_fontconfig_fonts()
             if sys.platform == 'darwin':
@@ -1086,9 +1089,12 @@
         self.ttflist = []
 
         # Delay the warning by 5s.
-        timer = threading.Timer(5, lambda: _log.warning(
-            'Matplotlib is building the font cache; this may take a moment.'))
-        timer.start()
+        try:
+            timer = threading.Timer(5, lambda: _log.warning(
+                'Matplotlib is building the font cache; this may take a moment.'))
+            timer.start()
+        except RuntimeError:
+            timer = None
         try:
             for fontext in ["afm", "ttf"]:
                 for path in [*findSystemFonts(paths, fontext=fontext),
@@ -1101,7 +1107,8 @@
                         _log.info("Failed to extract font properties from %s: "
                                   "%s", path, exc)
         finally:
-            timer.cancel()
+            if timer:
+                timer.cancel()
 
     def addfont(self, path):
         """

diff --git a/lib/matplotlib/mlab.py b/lib/matplotlib/mlab.py
@@ -215,9 +215,9 @@ def _stride_windows(x, n, noverlap=0):
     x = np.asarray(x)
 
     _api.check_isinstance(Integral, n=n, noverlap=noverlap)
-    if not (1 <= n <= x.size and n < noverlap):
+    if not (1 <= n <= x.size and noverlap < n):
         raise ValueError(f'n ({n}) and noverlap ({noverlap}) must be positive integers '
-                         f'with n < noverlap and n <= x.size ({x.size})')
+                         f'with noverlap < n and n <= x.size ({x.size})')
 
     if n == 1 and noverlap == 0:
         return x[np.newaxis]

diff --git a/lib/matplotlib/testing/__init__.py b/lib/matplotlib/testing/__init__.py
@@ -87,9 +87,14 @@
 
     Raises
     ------
+    pytest.skip
+        If running on emscripten, which does not support subprocesses.
     pytest.xfail
         If platform is Cygwin and subprocess reports a fork() failure.
     """
+    if sys.platform == 'emscripten':
+        import pytest
+        pytest.skip('emscripten does not support subprocesses')
     if capture_output:
         stdout = stderr = subprocess.PIPE
     try:
@@ -177,7 +182,7 @@
     try:
         mpl.dviread.find_tex_file(f"{package}.sty")
         return True
-    except FileNotFoundError:
+    except (FileNotFoundError, OSError):
         return False
 
 

diff --git a/lib/matplotlib/testing/decorators.py b/lib/matplotlib/testing/decorators.py
@@ -138,6 +138,8 @@
             try:
                 if 'microsoft' in uname().release.lower():
                     raise OSError  # On WSL, symlink breaks silently
+                if sys.platform == 'emscripten':
+                    raise OSError
                 os.symlink(orig_expected_path, expected_fname)
             except OSError:  # On Windows, symlink *may* be unavailable.
                 shutil.copyfile(orig_expected_path, expected_fname)

diff --git a/lib/matplotlib/tests/test_animation.py b/lib/matplotlib/tests/test_animation.py
@@ -271,6 +271,8 @@
     anim.save('unused.null', writer=NullMovieWriter())
 
 
+@pytest.mark.skipif(sys.platform == 'emscripten',
+                    reason='emscripten does not support subprocesses')
 def test_movie_writer_registry():
     assert len(animation.writers._registered) > 0
     mpl.rcParams['animation.ffmpeg_path'] = "not_available_ever_xxxx"
@@ -522,6 +524,8 @@
 def test_movie_writer_invalid_path(anim):
     if sys.platform == "win32":
         match_str = r"\[WinError 3] .*\\\\foo\\\\bar\\\\aardvark'"
+    elif sys.platform == "emscripten":
+        match_str = r"\[Errno 44] .*'/foo"
     else:
         match_str = r"\[Errno 2] .*'/foo"
     with pytest.raises(FileNotFoundError, match=match_str):

diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -8277,7 +8277,7 @@ def test_normal_axes():
     ]
     for nn, b in enumerate(bbaxis):
         targetbb = mtransforms.Bbox.from_bounds(*target[nn])
-        assert_array_almost_equal(b.bounds, targetbb.bounds, decimal=2)
+        assert_array_almost_equal(b.bounds, targetbb.bounds, decimal=1)
 
     target = [
         [150.0, 119.999, 930.0, 11.111],
@@ -8295,7 +8295,7 @@ def test_normal_axes():
 
     target = [85.5138, 75.88888, 1021.11, 1017.11]
     targetbb = mtransforms.Bbox.from_bounds(*target)
-    assert_array_almost_equal(bbtb.bounds, targetbb.bounds, decimal=2)
+    assert_array_almost_equal(bbtb.bounds, targetbb.bounds, decimal=1)
 
     # test that get_position roundtrips to get_window_extent
     axbb = ax.get_position().transformed(fig.transFigure).bounds

diff --git a/lib/matplotlib/tests/test_backend_pdf.py b/lib/matplotlib/tests/test_backend_pdf.py
@@ -1,7 +1,6 @@
 import datetime
 import decimal
 import io
-import os
 from pathlib import Path
 
 import numpy as np
@@ -291,8 +290,8 @@ def test_text_urls_tex():
             assert annot.Rect[1] == decimal.Decimal('0.7') * 72
 
 
-def test_pdfpages_fspath():
-    with PdfPages(Path(os.devnull)) as pdf:
+def test_pdfpages_fspath(tmp_path):
+    with PdfPages(tmp_path / 'unused.pdf') as pdf:
         pdf.savefig(plt.figure())
 
 

diff --git a/lib/matplotlib/tests/test_dviread.py b/lib/matplotlib/tests/test_dviread.py
@@ -1,6 +1,7 @@
 import json
 from pathlib import Path
 import shutil
+import sys
 
 import matplotlib.dviread as dr
 import pytest
@@ -60,7 +61,7 @@ def test_PsfontsMap(monkeypatch):
         fontmap[b'%']
 
 
-@pytest.mark.skipif(shutil.which("kpsewhich") is None,
+@pytest.mark.skipif(sys.platform == "emscripten" or shutil.which("kpsewhich") is None,
                     reason="kpsewhich is not available")
 def test_dviread():
     dirpath = Path(__file__).parent / 'baseline_images/dviread'

diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -3,6 +3,7 @@
 import io
 import pickle
 import platform
+import sys
 from threading import Timer
 from types import SimpleNamespace
 import warnings
@@ -1605,6 +1606,8 @@ def test_add_axes_kwargs():
     plt.close()
 
 
+@pytest.mark.skipif(sys.platform == 'emscripten',
+                    reason='emscripten does not support threads')
 def test_ginput(recwarn):  # recwarn undoes warn filters at exit.
     warnings.filterwarnings("ignore", "cannot show the figure")
     fig, ax = plt.subplots()
@@ -1627,6 +1630,8 @@ def multi_presses():
     np.testing.assert_allclose(fig.ginput(3), [(.3, .4), (.5, .6)])
 
 
+@pytest.mark.skipif(sys.platform == 'emscripten',
+                    reason='emscripten does not support threads')
 def test_waitforbuttonpress(recwarn):  # recwarn undoes warn filters at exit.
     warnings.filterwarnings("ignore", "cannot show the figure")
     fig = plt.figure()

diff --git a/lib/matplotlib/tests/test_font_manager.py b/lib/matplotlib/tests/test_font_manager.py
@@ -20,7 +20,7 @@
 from matplotlib.testing import subprocess_run_helper, subprocess_run_for_testing
 
 
-has_fclist = shutil.which('fc-list') is not None
+has_fclist = sys.platform != 'emscripten' and shutil.which('fc-list') is not None
 
 
 def test_font_priority():
@@ -228,6 +228,8 @@ def _model_handler(_):
     plt.close()
 
 
+@pytest.mark.skipif(sys.platform == 'emscripten',
+                    reason='emscripten does not support subprocesses')
 @pytest.mark.skipif(not hasattr(os, "register_at_fork"),
                     reason="Cannot register at_fork handlers")
 def test_fork():

diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -215,8 +215,8 @@ def test_imsave_rgba_origin(origin):
 
 
 @pytest.mark.parametrize("fmt", ["png", "pdf", "ps", "eps", "svg"])
-def test_imsave_fspath(fmt):
-    plt.imsave(Path(os.devnull), np.array([[0, 1]]), format=fmt)
+def test_imsave_fspath(fmt, tmp_path):
+    plt.imsave(tmp_path / f'unused.{fmt}', np.array([[0, 1]]), format=fmt)
 
 
 def test_imsave_color_alpha():

diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -513,10 +513,10 @@ def test_figure_legend_outside():
         leg = fig.legend(loc='outside ' + todo)
         fig.draw_without_rendering()
 
-        assert_allclose(axs.get_window_extent().extents,
-                        axbb[nn])
-        assert_allclose(leg.get_window_extent().extents,
-                        legbb[nn])
+        assert_allclose(axs.get_window_extent().extents, axbb[nn],
+                        rtol=1e-4)
+        assert_allclose(leg.get_window_extent().extents, legbb[nn],
+                        rtol=1e-4)
 
 
 @image_comparison(['legend_stackplot.png'],

diff --git a/lib/matplotlib/tests/test_matplotlib.py b/lib/matplotlib/tests/test_matplotlib.py
@@ -19,9 +19,9 @@ def test_parse_to_version_info(version_str, version_tuple):
     assert matplotlib._parse_to_version_info(version_str) == version_tuple
 
 
-@pytest.mark.skipif(sys.platform == "win32",
-                    reason="chmod() doesn't work as is on Windows")
-@pytest.mark.skipif(sys.platform != "win32" and os.geteuid() == 0,
+@pytest.mark.skipif(sys.platform not in ["linux", "darwin"],
+                    reason="chmod() doesn't work on this platform")
+@pytest.mark.skipif(sys.platform in ["linux", "darwin"] and os.geteuid() == 0,
                     reason="chmod() doesn't work as root")
 def test_tmpconfigdir_warning(tmp_path):
     """Test that a warning is emitted if a temporary configdir must be used."""