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gh-140146: Use Tcl_CreateChannelHandler to enable piping to stdin with tkinter on Windows #140147

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gh-140146: Use Tcl_CreateChannelHandler to enable piping to stdin with tkinter on Windows #140147

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d8ac586
replace Tcl_CreateFileHandler by Tcl_CreateChannelHandler
Oct 13, 2025
c3d637b
rename MyFileProc to MyChannelProc
Oct 13, 2025
d356c71
add test script
Oct 15, 2025
002eb6c
rename test script to be consistent with existing test script names
Oct 15, 2025
72d6f9c
📜🤖 Added by blurb_it.
blurb-it[bot] Oct 15, 2025
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34 changes: 34 additions & 0 deletions Lib/test/test_tkinter/test_stdin_pipe.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
import unittest
import subprocess
import sys
from test import support
from test.support import import_helper

tkinter = import_helper.import_module("tkinter")


@unittest.skipUnless(support.has_subprocess_support, "test requires subprocess")
class TkStdinPipe(unittest.TestCase):

def test_pipe_stdin(self):
proc = subprocess.Popen([sys.executable, "-i"],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
proc.stdin.write(b"import tkinter\n")
proc.stdin.write(b"interpreter = tkinter.Tcl()\n")
proc.stdin.write(b"print('hello')\n")
proc.stdin.write(b"quit()\n")

stdout, stderr = proc.communicate()
stdout = stdout.decode()
stderr = stderr.decode()

if proc.returncode != 0:
self.fail(f"Child exited with {proc.returncode}\nSTDOUT:\n{out}\nSTDERR:\n{err}")

self.assertEqual(stdout.rstrip(), "hello")


if __name__ == "__main__":
unittest.main()
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Windows/2025-10-15-07-18-56.gh-issue-140146.afBk12.rst
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@@ -0,0 +1 @@
Replaces ``Tcl_CreateFileHandler`` in the ``EventHook`` function in ``Modules/_tkinter.c`` by ``Tcl_CreateChannelHandler``, as the former is Unix-specific and the latter is platform-independent. This cleans up the code in ``Modules/_tkinter.c``, and also allows stdin to be used as a pipe on all platforms. Patch by Michiel de Hoon.
52 changes: 7 additions & 45 deletions Modules/_tkinter.c
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Original file line number Diff line number Diff line change
Expand Up @@ -76,18 +76,6 @@ typedef int Tcl_Size;
#define TCL_SIZE_MAX INT_MAX
#endif

#if !(defined(MS_WINDOWS) || defined(__CYGWIN__))
#define HAVE_CREATEFILEHANDLER
#endif

#ifdef HAVE_CREATEFILEHANDLER

/* If Tcl can wait for a Unix file descriptor, define the EventHook() routine
which uses this to handle Tcl events while the user is typing commands. */

#define WAIT_FOR_STDIN

#endif /* HAVE_CREATEFILEHANDLER */

/* Use OS native encoding for converting between Python strings and
Tcl objects.
Expand All @@ -108,8 +96,6 @@ typedef int Tcl_Size;
#endif

#ifdef MS_WINDOWS
#include <conio.h>
#define WAIT_FOR_STDIN

static PyObject *
_get_tcl_lib_path(void)
Expand Down Expand Up @@ -3325,41 +3311,25 @@ static PyMethodDef moduleMethods[] =
{NULL, NULL}
};

#ifdef WAIT_FOR_STDIN

static int stdin_ready = 0;

#ifndef MS_WINDOWS
static void
MyFileProc(void *clientData, int mask)
MyChannelProc(void *clientData, int mask)
{
stdin_ready = 1;
int* stdin_ready = clientData;
*stdin_ready = 1;
}
#endif

static PyThreadState *event_tstate = NULL;

static int
EventHook(void)
{
#ifndef MS_WINDOWS
int tfile;
#endif
int stdin_ready = 0;
Tcl_Channel channel = Tcl_GetStdChannel(TCL_STDIN);
PyEval_RestoreThread(event_tstate);
stdin_ready = 0;
errorInCmd = 0;
#ifndef MS_WINDOWS
tfile = fileno(stdin);
Tcl_CreateFileHandler(tfile, TCL_READABLE, MyFileProc, NULL);
#endif
Tcl_CreateChannelHandler(channel, TCL_READABLE, MyChannelProc, &stdin_ready);
while (!errorInCmd && !stdin_ready) {
int result;
#ifdef MS_WINDOWS
if (_kbhit()) {
stdin_ready = 1;
break;
}
#endif
Py_BEGIN_ALLOW_THREADS
if(tcl_lock)PyThread_acquire_lock(tcl_lock, 1);
tcl_tstate = event_tstate;
Expand All @@ -3375,9 +3345,7 @@ EventHook(void)
if (result < 0)
break;
}
#ifndef MS_WINDOWS
Tcl_DeleteFileHandler(tfile);
#endif
Tcl_DeleteChannelHandler(channel, MyChannelProc, &stdin_ready);
if (errorInCmd) {
errorInCmd = 0;
PyErr_SetRaisedException(excInCmd);
Expand All @@ -3388,27 +3356,21 @@ EventHook(void)
return 0;
}

#endif

static void
EnableEventHook(void)
{
#ifdef WAIT_FOR_STDIN
if (PyOS_InputHook == NULL) {
event_tstate = PyThreadState_Get();
PyOS_InputHook = EventHook;
}
#endif
}

static void
DisableEventHook(void)
{
#ifdef WAIT_FOR_STDIN
if (Tk_GetNumMainWindows() == 0 && PyOS_InputHook == EventHook) {
PyOS_InputHook = NULL;
}
#endif
}

static int
Expand Down
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