Backport PR #27221: FIX: Enable interrupts on macosx event loops

ksunden · meeseeksmachine · commit 276e9286cd2d · 2023-10-30T18:40:50.000Z
diff --git a/lib/matplotlib/backends/backend_macosx.py b/lib/matplotlib/backends/backend_macosx.py
@@ -1,3 +1,4 @@
+import contextlib
 import os
 import signal
 import socket
@@ -106,6 +107,13 @@ def resize(self, width, height):
         ResizeEvent("resize_event", self)._process()
         self.draw_idle()
 
+    def start_event_loop(self, timeout=0):
+        # docstring inherited
+        with _maybe_allow_interrupt():
+            # Call the objc implementation of the event loop after
+            # setting up the interrupt handling
+            self._start_event_loop(timeout=timeout)
+
 
 class NavigationToolbar2Mac(_macosx.NavigationToolbar2, NavigationToolbar2):
 
@@ -171,34 +179,8 @@ def start_main_loop(cls):
         # Set up a SIGINT handler to allow terminating a plot via CTRL-C.
         # The logic is largely copied from qt_compat._maybe_allow_interrupt; see its
         # docstring for details.  Parts are implemented by wake_on_fd_write in ObjC.
-
-        old_sigint_handler = signal.getsignal(signal.SIGINT)
-        if old_sigint_handler in (None, signal.SIG_IGN, signal.SIG_DFL):
-            _macosx.show()
-            return
-
-        handler_args = None
-        wsock, rsock = socket.socketpair()
-        wsock.setblocking(False)
-        rsock.setblocking(False)
-        old_wakeup_fd = signal.set_wakeup_fd(wsock.fileno())
-        _macosx.wake_on_fd_write(rsock.fileno())
-
-        def handle(*args):
-            nonlocal handler_args
-            handler_args = args
-            _macosx.stop()
-
-        signal.signal(signal.SIGINT, handle)
-        try:
+        with _maybe_allow_interrupt():
             _macosx.show()
-        finally:
-            wsock.close()
-            rsock.close()
-            signal.set_wakeup_fd(old_wakeup_fd)
-            signal.signal(signal.SIGINT, old_sigint_handler)
-            if handler_args is not None:
-                old_sigint_handler(*handler_args)
 
     def show(self):
         if not self._shown:
@@ -208,6 +190,45 @@ def show(self):
             self._raise()
 
 
+@contextlib.contextmanager
+def _maybe_allow_interrupt():
+    """
+    This manager allows to terminate a plot by sending a SIGINT. It is
+    necessary because the running backend prevents Python interpreter to
+    run and process signals (i.e., to raise KeyboardInterrupt exception). To
+    solve this one needs to somehow wake up the interpreter and make it close
+    the plot window. The implementation is taken from qt_compat, see that
+    docstring for a more detailed description.
+    """
+    old_sigint_handler = signal.getsignal(signal.SIGINT)
+    if old_sigint_handler in (None, signal.SIG_IGN, signal.SIG_DFL):
+        yield
+        return
+
+    handler_args = None
+    wsock, rsock = socket.socketpair()
+    wsock.setblocking(False)
+    rsock.setblocking(False)
+    old_wakeup_fd = signal.set_wakeup_fd(wsock.fileno())
+    _macosx.wake_on_fd_write(rsock.fileno())
+
+    def handle(*args):
+        nonlocal handler_args
+        handler_args = args
+        _macosx.stop()
+
+    signal.signal(signal.SIGINT, handle)
+    try:
+        yield
+    finally:
+        wsock.close()
+        rsock.close()
+        signal.set_wakeup_fd(old_wakeup_fd)
+        signal.signal(signal.SIGINT, old_sigint_handler)
+        if handler_args is not None:
+            old_sigint_handler(*handler_args)
+
+
 @_Backend.export
 class _BackendMac(_Backend):
     FigureCanvas = FigureCanvasMac
diff --git a/src/_macosx.m b/src/_macosx.m
@@ -451,7 +451,7 @@ int mpl_check_modifier(
 }
 
 static PyObject*
-FigureCanvas_start_event_loop(FigureCanvas* self, PyObject* args, PyObject* keywords)
+FigureCanvas__start_event_loop(FigureCanvas* self, PyObject* args, PyObject* keywords)
 {
     float timeout = 0.0;
 
@@ -522,8 +522,8 @@ int mpl_check_modifier(
          (PyCFunction)FigureCanvas_remove_rubberband,
          METH_NOARGS,
          "Remove the current rubberband rectangle."},
-        {"start_event_loop",
-         (PyCFunction)FigureCanvas_start_event_loop,
+        {"_start_event_loop",
+         (PyCFunction)FigureCanvas__start_event_loop,
          METH_KEYWORDS | METH_VARARGS,
          NULL},  // docstring inherited
         {"stop_event_loop",
