matplotlib · ksunden · Jul 16, 2023 · Jun 1, 2023 · Jun 2, 2023 · Jun 3, 2023
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1164,7 +1164,8 @@ def interval(self):
     def interval(self, interval):
         # Force to int since none of the backends actually support fractional
         # milliseconds, and some error or give warnings.
-        interval = int(interval)
+        # Some backends also fail when interval == 0, so ensure >= 1 msec
+        interval = max(int(interval), 1)
         self._interval = interval
         self._timer_set_interval()
 

diff --git a/lib/matplotlib/backends/backend_macosx.py b/lib/matplotlib/backends/backend_macosx.py
@@ -69,6 +69,7 @@ def callback_func(callback, timer):
             self._timers.remove(timer)
             timer.stop()
         timer = self.new_timer(interval=0)
+        timer.single_shot = True
         timer.add_callback(callback_func, callback, timer)
         self._timers.add(timer)
         timer.start()

diff --git a/lib/matplotlib/tests/test_backends_interactive.py b/lib/matplotlib/tests/test_backends_interactive.py
@@ -624,3 +624,48 @@ def test_figure_leak_20490(env, time_mem):
 
     growth = int(result.stdout)
     assert growth <= acceptable_memory_leakage
+
+
+def _impl_test_interactive_timers():
+    # A timer with <1 millisecond gets converted to int and therefore 0
+    # milliseconds, which the mac framework interprets as singleshot.
+    # We only want singleshot if we specify that ourselves, otherwise we want
+    # a repeating timer
+    import os
+    from unittest.mock import Mock
+    import matplotlib.pyplot as plt
+    # increase pause duration on CI to let things spin up
+    # particularly relevant for gtk3cairo
+    pause_time = 2 if os.getenv("CI") else 0.5
+    fig = plt.figure()
+    plt.pause(pause_time)
+    timer = fig.canvas.new_timer(0.1)
+    mock = Mock()
+    timer.add_callback(mock)
+    timer.start()
+    plt.pause(pause_time)
+    timer.stop()
+    assert mock.call_count > 1
+
+    # Now turn it into a single shot timer and verify only one gets triggered
+    mock.call_count = 0
+    timer.single_shot = True
+    timer.start()
+    plt.pause(pause_time)
+    assert mock.call_count == 1
+
+    # Make sure we can start the timer a second time
+    timer.start()
+    plt.pause(pause_time)
+    assert mock.call_count == 2
+    plt.close("all")
+
+
+@pytest.mark.parametrize("env", _get_testable_interactive_backends())
+def test_interactive_timers(env):
+    if env["MPLBACKEND"] == "gtk3cairo" and os.getenv("CI"):
+        pytest.skip("gtk3cairo timers do not work in remote CI")
+    if env["MPLBACKEND"] == "wx":
+        pytest.skip("wx backend is deprecated; tests failed on appveyor")
+    _run_helper(_impl_test_interactive_timers,
+                timeout=_test_timeout, extra_env=env)
diff --git a/src/_macosx.m b/src/_macosx.m
@@ -1811,93 +1811,53 @@ - (void)flagsChanged:(NSEvent *)event
 
 typedef struct {
     PyObject_HEAD
-    CFRunLoopTimerRef timer;
+    NSTimer* timer;
+
 } Timer;
 
 static PyObject*
 Timer_new(PyTypeObject* type, PyObject *args, PyObject *kwds)
 {
     lazy_init();
     Timer* self = (Timer*)type->tp_alloc(type, 0);
-    if (!self) { return NULL; }
+    if (!self) {
+        return NULL;
+    }
     self->timer = NULL;
     return (PyObject*) self;
 }
 
 static PyObject*
 Timer_repr(Timer* self)
 {
-    return PyUnicode_FromFormat("Timer object %p wrapping CFRunLoopTimerRef %p",
+    return PyUnicode_FromFormat("Timer object %p wrapping NSTimer %p",
                                (void*) self, (void*)(self->timer));
 }
 
-static void timer_callback(CFRunLoopTimerRef timer, void* info)
-{
-    gil_call_method(info, "_on_timer");
-}
-
-static void context_cleanup(const void* info)
-{
-    Py_DECREF((PyObject*)info);
-}
-
 static PyObject*
 Timer__timer_start(Timer* self, PyObject* args)
 {
-    CFRunLoopRef runloop;
-    CFRunLoopTimerRef timer;
-    CFRunLoopTimerContext context;
-    CFAbsoluteTime firstFire;
-    CFTimeInterval interval;
+    NSTimeInterval interval;
     PyObject* py_interval = NULL, * py_single = NULL, * py_on_timer = NULL;
     int single;
-    runloop = CFRunLoopGetMain();
-    if (!runloop) {
-        PyErr_SetString(PyExc_RuntimeError, "Failed to obtain run loop");
-        return NULL;
-    }
     if (!(py_interval = PyObject_GetAttrString((PyObject*)self, "_interval"))
         || ((interval = PyFloat_AsDouble(py_interval) / 1000.), PyErr_Occurred())
         || !(py_single = PyObject_GetAttrString((PyObject*)self, "_single"))
         || ((single = PyObject_IsTrue(py_single)) == -1)
         || !(py_on_timer = PyObject_GetAttrString((PyObject*)self, "_on_timer"))) {
         goto exit;
     }
-    // (current time + interval) is time of first fire.
-    firstFire = CFAbsoluteTimeGetCurrent() + interval;
-    if (single) {
-        interval = 0;
-    }
     if (!PyMethod_Check(py_on_timer)) {
         PyErr_SetString(PyExc_RuntimeError, "_on_timer should be a Python method");
         goto exit;
     }
-    Py_INCREF(self);
-    context.version = 0;
-    context.retain = NULL;
-    context.release = context_cleanup;
-    context.copyDescription = NULL;
-    context.info = self;
-    timer = CFRunLoopTimerCreate(kCFAllocatorDefault,
-                                 firstFire,
-                                 interval,
-                                 0,
-                                 0,
-                                 timer_callback,
-                                 &context);
-    if (!timer) {
-        PyErr_SetString(PyExc_RuntimeError, "Failed to create timer");
-        goto exit;
-    }
-    if (self->timer) {
-        CFRunLoopTimerInvalidate(self->timer);
-        CFRelease(self->timer);
-    }
-    CFRunLoopAddTimer(runloop, timer, kCFRunLoopCommonModes);
-    /* Don't release the timer here, since the run loop may be destroyed and
-     * the timer lost before we have a chance to decrease the reference count
-     * of the attribute */
-    self->timer = timer;
+
+    // hold a reference to the timer so we can invalidate/stop it later
+    self->timer = [NSTimer scheduledTimerWithTimeInterval: interval
+                                            repeats: !single
+                                              block: ^(NSTimer *timer) {
+        gil_call_method((PyObject*)self, "_on_timer");
+    }];
 exit:
     Py_XDECREF(py_interval);
     Py_XDECREF(py_single);
@@ -1913,8 +1873,7 @@ static void context_cleanup(const void* info)
 Timer__timer_stop(Timer* self)
 {
     if (self->timer) {
-        CFRunLoopTimerInvalidate(self->timer);
-        CFRelease(self->timer);
+        [self->timer invalidate];
         self->timer = NULL;
     }
     Py_RETURN_NONE;
@@ -1935,7 +1894,7 @@ static void context_cleanup(const void* info)
     .tp_repr = (reprfunc)Timer_repr,
     .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
     .tp_new = (newfunc)Timer_new,
-    .tp_doc = "A Timer object wraps a CFRunLoopTimerRef and can add it to the event loop.",
+    .tp_doc = "A Timer object that contains an NSTimer that gets added to the event loop when started.",
     .tp_methods = (PyMethodDef[]){  // All docstrings are inherited.
         {"_timer_start",
          (PyCFunction)Timer__timer_start,