[3.13] gh-134210: handle signals in _curses.window.getch (GH-134326) (#134784)

(cherry picked from commit 51762b6)

Author: picnixz

Misc/NEWS.d/next/Library/2025-05-24-13-10-35.gh-issue-134210.0IuMY2.rst

@@ -0,0 +1,2 @@
+:func:`curses.window.getch` now correctly handles signals. Patch by Bénédikt
+Tran.

Modules/_cursesmodule.c

@@ -1385,7 +1385,7 @@ _curses_window_getbkgd_impl(PyCursesWindowObject *self)
 }
 
 /*[clinic input]
-_curses.window.getch -> int
+_curses.window.getch
 
     [
     y: int
@@ -1402,10 +1402,10 @@ keypad keys and so on return numbers higher than 256.  In no-delay mode, -1
 is returned if there is no input, else getch() waits until a key is pressed.
 [clinic start generated code]*/
 
-static int
+static PyObject *
 _curses_window_getch_impl(PyCursesWindowObject *self, int group_right_1,
                           int y, int x)
-/*[clinic end generated code: output=980aa6af0c0ca387 input=bb24ebfb379f991f]*/
+/*[clinic end generated code: output=e1639e87d545e676 input=73f350336b1ee8c8]*/
 {
     int rtn;
 
@@ -1418,7 +1418,17 @@ _curses_window_getch_impl(PyCursesWindowObject *self, int group_right_1,
     }
     Py_END_ALLOW_THREADS
 
-    return rtn;
+    if (rtn == ERR) {
+        // We suppress ERR returned by wgetch() in nodelay mode
+        // after we handled possible interruption signals.
+        if (PyErr_CheckSignals()) {
+            return NULL;
+        }
+        // ERR is an implementation detail, so to be on the safe side,
+        // we forcibly set the return value to -1 as documented above.
+        rtn = -1;
+    }
+    return PyLong_FromLong(rtn);
 }
 
 /*[clinic input]