gh-133139: Add curses.assume_default_colors() (GH-133145)

This is a refinement of the curses.use_default_colors() function which
allows to change the color pair 0.

Modules/_cursesmodule.c

@@ -4720,15 +4720,12 @@ _curses_use_env_impl(PyObject *module, int flag)
 /*[clinic input]
 _curses.use_default_colors
 
-Allow use of default values for colors on terminals supporting this feature.
-
-Use this to support transparency in your application.  The default color
-is assigned to the color number -1.
+Equivalent to assume_default_colors(-1, -1).
 [clinic start generated code]*/
 
 static PyObject *
 _curses_use_default_colors_impl(PyObject *module)
-/*[clinic end generated code: output=a3b81ff71dd901be input=656844367470e8fc]*/
+/*[clinic end generated code: output=a3b81ff71dd901be input=99ff0b7c69834d1f]*/
 {
     int code;
 
@@ -4744,6 +4741,39 @@ _curses_use_default_colors_impl(PyObject *module)
         return NULL;
     }
 }
+
+/*[clinic input]
+_curses.assume_default_colors
+    fg: int
+    bg: int
+    /
+
+Allow use of default values for colors on terminals supporting this feature.
+
+Assign terminal default foreground/background colors to color number -1.
+Change the definition of the color-pair 0 to (fg, bg).
+
+Use this to support transparency in your application.
+[clinic start generated code]*/
+
+static PyObject *
+_curses_assume_default_colors_impl(PyObject *module, int fg, int bg)
+/*[clinic end generated code: output=54985397a7d2b3a5 input=7fe301712ef3e9fb]*/
+{
+    int code;
+
+    PyCursesStatefulInitialised(module);
+    PyCursesStatefulInitialisedColor(module);
+
+    code = assume_default_colors(fg, bg);
+    if (code != ERR) {
+        Py_RETURN_NONE;
+    } else {
+        cursesmodule_state *state = get_cursesmodule_state(module);
+        PyErr_SetString(state->error, "assume_default_colors() returned ERR");
+        return NULL;
+    }
+}
 #endif /* STRICT_SYSV_CURSES */
 
 
@@ -4902,6 +4932,7 @@ static PyMethodDef cursesmodule_methods[] = {
     _CURSES_UNGET_WCH_METHODDEF
     _CURSES_USE_ENV_METHODDEF
     _CURSES_USE_DEFAULT_COLORS_METHODDEF
+    _CURSES_ASSUME_DEFAULT_COLORS_METHODDEF
     {NULL,                  NULL}         /* sentinel */
 };