Merge pull request matplotlib#28819 from QuLogic/freethread

Mark all extensions as free-threading safe

Author: ianthomas23

.github/workflows/cibuildwheel.yml

@@ -148,8 +148,6 @@ jobs:
           package-dir: dist/${{ needs.build_sdist.outputs.SDIST_NAME }}
         env:
           CIBW_BUILD: "cp313-* cp313t-*"
-          # No free-threading wheels for NumPy; musllinux skipped for main builds also.
-          CIBW_SKIP: "cp313t-win_amd64 *-musllinux_aarch64"
           CIBW_BUILD_FRONTEND:
             "pip; args: --pre --extra-index-url https://pypi.anaconda.org/scientific-python-nightly-wheels/simple"
           CIBW_FREE_THREADED_SUPPORT: true

doc/users/next_whats_new/freethreading.rst

@@ -0,0 +1,22 @@
+Preliminary support for free-threaded CPython 3.13
+--------------------------------------------------
+
+Matplotlib 3.10 has preliminary support for the free-threaded build of CPython 3.13. See
+https://py-free-threading.github.io, `PEP 703 <https://peps.python.org/pep-0703/>`_ and
+the `CPython 3.13 release notes
+<https://docs.python.org/3.13/whatsnew/3.13.html#free-threaded-cpython>`_ for more detail
+about free-threaded Python.
+
+Support for free-threaded Python does not mean that Matplotlib is wholly thread safe. We
+expect that use of a Figure within a single thread will work, and though input data is
+usually copied, modification of data objects used for a plot from another thread may
+cause inconsistencies in cases where it is not. Use of any global state (such as the
+``pyplot`` module) is highly discouraged and unlikely to work consistently. Also note
+that most GUI toolkits expect to run on the main thread, so interactive usage may be
+limited or unsupported from other threads.
+
+If you are interested in free-threaded Python, for example because you have a
+multiprocessing-based workflow that you are interested in running with Python threads, we
+encourage testing and experimentation. If you run into problems that you suspect are
+because of Matplotlib, please open an issue, checking first if the bug also occurs in the
+“regular” non-free-threaded CPython 3.13 build.

src/_backend_agg_wrapper.cpp

@@ -185,7 +185,7 @@ PyRendererAgg_draw_gouraud_triangles(RendererAgg *self,
     self->draw_gouraud_triangles(gc, points, colors, trans);
 }
 
-PYBIND11_MODULE(_backend_agg, m)
+PYBIND11_MODULE(_backend_agg, m, py::mod_gil_not_used())
 {
     py::class_<RendererAgg>(m, "RendererAgg", py::buffer_protocol())
         .def(py::init<unsigned int, unsigned int, double>(),

src/_c_internal_utils.cpp

@@ -196,7 +196,7 @@ mpl_SetProcessDpiAwareness_max(void)
 #endif
 }
 
-PYBIND11_MODULE(_c_internal_utils, m)
+PYBIND11_MODULE(_c_internal_utils, m, py::mod_gil_not_used())
 {
     m.def(
         "display_is_valid", &mpl_display_is_valid,

src/_image_wrapper.cpp

@@ -200,7 +200,8 @@ image_resample(py::array input_array,
 }
 
 
-PYBIND11_MODULE(_image, m) {
+PYBIND11_MODULE(_image, m, py::mod_gil_not_used())
+{
     py::enum_<interpolation_e>(m, "_InterpolationType")
         .value("NEAREST", NEAREST)
         .value("BILINEAR", BILINEAR)

src/_path_wrapper.cpp

@@ -368,7 +368,7 @@ Py_is_sorted_and_has_non_nan(py::object obj)
     return result;
 }
 
-PYBIND11_MODULE(_path, m)
+PYBIND11_MODULE(_path, m, py::mod_gil_not_used())
 {
     m.def("point_in_path", &Py_point_in_path,
           "x"_a, "y"_a, "radius"_a, "path"_a, "trans"_a);

src/_qhull_wrapper.cpp

@@ -276,7 +276,8 @@ delaunay(const CoordArray& x, const CoordArray& y, int verbose)
     return delaunay_impl(npoints, x.data(), y.data(), verbose == 0);
 }
 
-PYBIND11_MODULE(_qhull, m) {
+PYBIND11_MODULE(_qhull, m, py::mod_gil_not_used())
+{
     m.doc() = "Computing Delaunay triangulations.\n";
 
     m.def("delaunay", &delaunay, "x"_a, "y"_a, "verbose"_a,

src/_tkagg.cpp

@@ -333,7 +333,7 @@ load_tkinter_funcs()
 }
 #endif // end not Windows
 
-PYBIND11_MODULE(_tkagg, m)
+PYBIND11_MODULE(_tkagg, m, py::mod_gil_not_used())
 {
     try {
         load_tkinter_funcs();

src/ft2font_wrapper.cpp

@@ -952,7 +952,7 @@ PyFT2Font_fname(PyFT2Font *self)
     }
 }
 
-PYBIND11_MODULE(ft2font, m)
+PYBIND11_MODULE(ft2font, m, py::mod_gil_not_used())
 {
     if (FT_Init_FreeType(&_ft2Library)) {  // initialize library
         throw std::runtime_error("Could not initialize the freetype2 library");

src/tri/_tri_wrapper.cpp

@@ -2,7 +2,8 @@
 
 using namespace pybind11::literals;
 
-PYBIND11_MODULE(_tri, m) {
+PYBIND11_MODULE(_tri, m, py::mod_gil_not_used())
+{
     py::class_<Triangulation>(m, "Triangulation", py::is_final())
         .def(py::init<const Triangulation::CoordinateArray&,
                       const Triangulation::CoordinateArray&,