Modules/_tkinter.c

/***********************************************************
Copyright (C) 1994 Steen Lumholt.

                        All Rights Reserved

******************************************************************/

/* _tkinter.c -- Interface to libtk.a and libtcl.a. */

/* TCL/TK VERSION INFO:

    Only Tcl/Tk 8.3.1 and later are supported.  Older versions are not
    supported. Use Python 2.6 or older if you cannot upgrade your
    Tcl/Tk libraries.
*/

/* XXX Further speed-up ideas, involving Tcl 8.0 features:

   - Register a new Tcl type, "Python callable", which can be called more
   efficiently and passed to Tcl_EvalObj() directly (if this is possible).

*/


#include "Python.h"
#include <ctype.h>

#ifdef WITH_THREAD
#include "pythread.h"
#endif

#ifdef MS_WINDOWS
#include <windows.h>
#endif

#define CHECK_SIZE(size, elemsize) \
    ((size_t)(size) <= Py_MAX((size_t)INT_MAX, UINT_MAX / (size_t)(elemsize)))

/* Starting with Tcl 8.4, many APIs offer const-correctness.  Unfortunately,
   making _tkinter correct for this API means to break earlier
   versions. USE_COMPAT_CONST allows to make _tkinter work with both 8.4 and
   earlier versions. Once Tcl releases before 8.4 don't need to be supported
   anymore, this should go. */
#define USE_COMPAT_CONST

/* If Tcl is compiled for threads, we must also define TCL_THREAD. We define
   it always; if Tcl is not threaded, the thread functions in
   Tcl are empty.  */
#define TCL_THREADS

#ifdef TK_FRAMEWORK
#include <Tcl/tcl.h>
#include <Tk/tk.h>
#else
#include <tcl.h>
#include <tk.h>
#endif

#include "tkinter.h"

/* For Tcl 8.2 and 8.3, CONST* is not defined (except on Cygwin). */
#ifndef CONST84_RETURN
#define CONST84_RETURN
#undef CONST
#define CONST
#endif

#if TK_VERSION_HEX < 0x08030102
#error "Tk older than 8.3.1 not supported"
#endif

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

#ifdef HAVE_CREATEFILEHANDLER

/* This bit is to ensure that TCL_UNIX_FD is defined and doesn't interfere
   with the proper calculation of FHANDLETYPE == TCL_UNIX_FD below. */
#ifndef TCL_UNIX_FD
#  ifdef TCL_WIN_SOCKET
#    define TCL_UNIX_FD (! TCL_WIN_SOCKET)
#  else
#    define TCL_UNIX_FD 1
#  endif
#endif

/* Tcl_CreateFileHandler() changed several times; these macros deal with the
   messiness.  In Tcl 8.0 and later, it is not available on Windows (and on
   Unix, only because Jack added it back); when available on Windows, it only
   applies to sockets. */

#ifdef MS_WINDOWS
#define FHANDLETYPE TCL_WIN_SOCKET
#else
#define FHANDLETYPE TCL_UNIX_FD
#endif

/* 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. */

#if FHANDLETYPE == TCL_UNIX_FD
#define WAIT_FOR_STDIN
#endif

#endif /* HAVE_CREATEFILEHANDLER */

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

#ifdef WITH_THREAD

/* The threading situation is complicated.  Tcl is not thread-safe, except
   when configured with --enable-threads.

   So we need to use a lock around all uses of Tcl.  Previously, the
   Python interpreter lock was used for this.  However, this causes
   problems when other Python threads need to run while Tcl is blocked
   waiting for events.

   To solve this problem, a separate lock for Tcl is introduced.
   Holding it is incompatible with holding Python's interpreter lock.
   The following four macros manipulate both locks together.

   ENTER_TCL and LEAVE_TCL are brackets, just like
   Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS.  They should be
   used whenever a call into Tcl is made that could call an event
   handler, or otherwise affect the state of a Tcl interpreter.  These
   assume that the surrounding code has the Python interpreter lock;
   inside the brackets, the Python interpreter lock has been released
   and the lock for Tcl has been acquired.

   Sometimes, it is necessary to have both the Python lock and the Tcl
   lock.  (For example, when transferring data from the Tcl
   interpreter result to a Python string object.)  This can be done by
   using different macros to close the ENTER_TCL block: ENTER_OVERLAP
   reacquires the Python lock (and restores the thread state) but
   doesn't release the Tcl lock; LEAVE_OVERLAP_TCL releases the Tcl
   lock.

   By contrast, ENTER_PYTHON and LEAVE_PYTHON are used in Tcl event
   handlers when the handler needs to use Python.  Such event handlers
   are entered while the lock for Tcl is held; the event handler
   presumably needs to use Python.  ENTER_PYTHON releases the lock for
   Tcl and acquires the Python interpreter lock, restoring the
   appropriate thread state, and LEAVE_PYTHON releases the Python
   interpreter lock and re-acquires the lock for Tcl.  It is okay for
   ENTER_TCL/LEAVE_TCL pairs to be contained inside the code between
   ENTER_PYTHON and LEAVE_PYTHON.

   These locks expand to several statements and brackets; they should
   not be used in branches of if statements and the like.

   If Tcl is threaded, this approach won't work anymore. The Tcl
   interpreter is only valid in the thread that created it, and all Tk
   activity must happen in this thread, also. That means that the
   mainloop must be invoked in the thread that created the
   interpreter. Invoking commands from other threads is possible;
   _tkinter will queue an event for the interpreter thread, which will
   then execute the command and pass back the result. If the main
   thread is not in the mainloop, and invoking commands causes an
   exception; if the main loop is running but not processing events,
   the command invocation will block.

   In addition, for a threaded Tcl, a single global tcl_tstate won't
   be sufficient anymore, since multiple Tcl interpreters may
   simultaneously dispatch in different threads. So we use the Tcl TLS
   API.

*/

static PyThread_type_lock tcl_lock = 0;

#ifdef TCL_THREADS
static Tcl_ThreadDataKey state_key;
typedef PyThreadState *ThreadSpecificData;
#define tcl_tstate \
    (*(PyThreadState**)Tcl_GetThreadData(&state_key, sizeof(PyThreadState*)))
#else
static PyThreadState *tcl_tstate = NULL;
#endif

#define ENTER_TCL \
    { PyThreadState *tstate = PyThreadState_Get(); Py_BEGIN_ALLOW_THREADS \
        if(tcl_lock)PyThread_acquire_lock(tcl_lock, 1); tcl_tstate = tstate;

#define LEAVE_TCL \
    tcl_tstate = NULL; \
    if(tcl_lock)PyThread_release_lock(tcl_lock); Py_END_ALLOW_THREADS}

#define ENTER_OVERLAP \
    Py_END_ALLOW_THREADS

#define LEAVE_OVERLAP_TCL \
    tcl_tstate = NULL; if(tcl_lock)PyThread_release_lock(tcl_lock); }

#define ENTER_PYTHON \
    { PyThreadState *tstate = tcl_tstate; tcl_tstate = NULL; \
        if(tcl_lock) \
          PyThread_release_lock(tcl_lock); PyEval_RestoreThread((tstate)); }

#define LEAVE_PYTHON \
    { PyThreadState *tstate = PyEval_SaveThread(); \
        if(tcl_lock)PyThread_acquire_lock(tcl_lock, 1); tcl_tstate = tstate; }

#define CHECK_TCL_APPARTMENT \
    if (((TkappObject *)self)->threaded && \
        ((TkappObject *)self)->thread_id != Tcl_GetCurrentThread()) { \
        PyErr_SetString(PyExc_RuntimeError, \
                        "Calling Tcl from different appartment"); \
        return 0; \
    }

#else

#define ENTER_TCL
#define LEAVE_TCL
#define ENTER_OVERLAP
#define LEAVE_OVERLAP_TCL
#define ENTER_PYTHON
#define LEAVE_PYTHON
#define CHECK_TCL_APPARTMENT

#endif

#ifndef FREECAST
#define FREECAST (char *)
#endif

/**** Tkapp Object Declaration ****/

static PyObject *Tkapp_Type;

typedef struct {
    PyObject_HEAD
    Tcl_Interp *interp;
    int wantobjects;
    int threaded; /* True if tcl_platform[threaded] */
    Tcl_ThreadId thread_id;
    int dispatching;
    /* We cannot include tclInt.h, as this is internal.
       So we cache interesting types here. */
    Tcl_ObjType *BooleanType;
    Tcl_ObjType *ByteArrayType;
    Tcl_ObjType *DoubleType;
    Tcl_ObjType *IntType;
    Tcl_ObjType *ListType;
    Tcl_ObjType *ProcBodyType;
    Tcl_ObjType *StringType;
} TkappObject;

#define Tkapp_Interp(v) (((TkappObject *) (v))->interp)
#define Tkapp_Result(v) Tcl_GetStringResult(Tkapp_Interp(v))

#define DEBUG_REFCNT(v) (printf("DEBUG: id=%p, refcnt=%i\n", \
(void *) v, Py_REFCNT(v)))



/**** Error Handling ****/

static PyObject *Tkinter_TclError;
static int quitMainLoop = 0;
static int errorInCmd = 0;
static PyObject *excInCmd;
static PyObject *valInCmd;
static PyObject *trbInCmd;

#ifdef TKINTER_PROTECT_LOADTK
static int tk_load_failed = 0;
#endif


static PyObject *
Tkinter_Error(PyObject *v)
{
    PyErr_SetString(Tkinter_TclError, Tkapp_Result(v));
    return NULL;
}



/**** Utils ****/

static int Tkinter_busywaitinterval = 20;

#ifdef WITH_THREAD
#ifndef MS_WINDOWS

/* Millisecond sleep() for Unix platforms. */

static void
Sleep(int milli)
{
    /* XXX Too bad if you don't have select(). */
    struct timeval t;
    t.tv_sec = milli/1000;
    t.tv_usec = (milli%1000) * 1000;
    select(0, (fd_set *)0, (fd_set *)0, (fd_set *)0, &t);
}
#endif /* MS_WINDOWS */

/* Wait up to 1s for the mainloop to come up. */

static int
WaitForMainloop(TkappObject* self)
{
    int i;
    for (i = 0; i < 10; i++) {
        if (self->dispatching)
            return 1;
        Py_BEGIN_ALLOW_THREADS
        Sleep(100);
        Py_END_ALLOW_THREADS
    }
    if (self->dispatching)
        return 1;
    PyErr_SetString(PyExc_RuntimeError, "main thread is not in main loop");
    return 0;
}
#endif /* WITH_THREAD */



#define ARGSZ 64



static PyObject *
unicodeFromTclStringAndSize(const char *s, Py_ssize_t size)
{
    PyObject *r = PyUnicode_DecodeUTF8(s, size, NULL);
    if (!r && PyErr_ExceptionMatches(PyExc_UnicodeDecodeError)) {
        /* Tcl encodes null character as \xc0\x80 */
        if (memchr(s, '\xc0', size)) {
            char *buf, *q;
            const char *e = s + size;
            PyErr_Clear();
            q = buf = (char *)PyMem_Malloc(size);
            if (buf == NULL) {
                PyErr_NoMemory();
                return NULL;
            }
            while (s != e) {
                if (s + 1 != e && s[0] == '\xc0' && s[1] == '\x80') {
                    *q++ = '\0';
                    s += 2;
                }
                else
                    *q++ = *s++;
            }
            s = buf;
            size = q - s;
            r = PyUnicode_DecodeUTF8(s, size, NULL);
            PyMem_Free(buf);
        }
    }
    return r;
}

static PyObject *
unicodeFromTclString(const char *s)
{
    return unicodeFromTclStringAndSize(s, strlen(s));
}

static PyObject *
unicodeFromTclObj(Tcl_Obj *value)
{
    int len;
    char *s = Tcl_GetStringFromObj(value, &len);
    return unicodeFromTclStringAndSize(s, len);
}


static PyObject *
Split(char *list)
{
    int argc;
    char **argv;
    PyObject *v;

    if (list == NULL) {
        Py_RETURN_NONE;
    }

    if (Tcl_SplitList((Tcl_Interp *)NULL, list, &argc, &argv) != TCL_OK) {
        /* Not a list.
         * Could be a quoted string containing funnies, e.g. {"}.
         * Return the string itself.
         */
        return unicodeFromTclString(list);
    }

    if (argc == 0)
        v = PyUnicode_FromString("");
    else if (argc == 1)
        v = unicodeFromTclString(argv[0]);
    else if ((v = PyTuple_New(argc)) != NULL) {
        int i;
        PyObject *w;

        for (i = 0; i < argc; i++) {
            if ((w = Split(argv[i])) == NULL) {
                Py_DECREF(v);
                v = NULL;
                break;
            }
            PyTuple_SetItem(v, i, w);
        }
    }
    Tcl_Free(FREECAST argv);
    return v;
}

/* In some cases, Tcl will still return strings that are supposed to
   be lists. SplitObj walks through a nested tuple, finding string
   objects that need to be split. */

static PyObject *
SplitObj(PyObject *arg)
{
    if (PyTuple_Check(arg)) {
        int i, size;
        PyObject *elem, *newelem, *result;

        size = PyTuple_Size(arg);
        result = NULL;
        /* Recursively invoke SplitObj for all tuple items.
           If this does not return a new object, no action is
           needed. */
        for(i = 0; i < size; i++) {
            elem = PyTuple_GetItem(arg, i);
            newelem = SplitObj(elem);
            if (!newelem) {
                Py_XDECREF(result);
                return NULL;
            }
            if (!result) {
                int k;
                if (newelem == elem) {
                    Py_DECREF(newelem);
                    continue;
                }
                result = PyTuple_New(size);
                if (!result)
                    return NULL;
                for(k = 0; k < i; k++) {
                    elem = PyTuple_GetItem(arg, k);
                    Py_INCREF(elem);
                    PyTuple_SetItem(result, k, elem);
                }
            }
            PyTuple_SetItem(result, i, newelem);
        }
        if (result)
            return result;
        /* Fall through, returning arg. */
    }
    else if (PyUnicode_Check(arg)) {
        int argc;
        char **argv;
        char *list = PyUnicode_AsUTF8(arg);

        if (list == NULL ||
            Tcl_SplitList((Tcl_Interp *)NULL, list, &argc, &argv) != TCL_OK) {
            Py_INCREF(arg);
            return arg;
        }
        Tcl_Free(FREECAST argv);
        if (argc > 1)
            return Split(list);
        /* Fall through, returning arg. */
    }
    else if (PyBytes_Check(arg)) {
        int argc;
        char **argv;
        char *list = PyBytes_AsString(arg);

        if (Tcl_SplitList((Tcl_Interp *)NULL, list, &argc, &argv) != TCL_OK) {
            Py_INCREF(arg);
            return arg;
        }
        Tcl_Free(FREECAST argv);
        if (argc > 1)
            return Split(PyBytes_AsString(arg));
        /* Fall through, returning arg. */
    }
    Py_INCREF(arg);
    return arg;
}


/**** Tkapp Object ****/

#ifndef WITH_APPINIT
int
Tcl_AppInit(Tcl_Interp *interp)
{
    const char * _tkinter_skip_tk_init;

    if (Tcl_Init(interp) == TCL_ERROR) {
        PySys_WriteStderr("Tcl_Init error: %s\n", Tcl_GetStringResult(interp));
        return TCL_ERROR;
    }

    _tkinter_skip_tk_init = Tcl_GetVar(interp,
                    "_tkinter_skip_tk_init", TCL_GLOBAL_ONLY);
    if (_tkinter_skip_tk_init != NULL &&
                    strcmp(_tkinter_skip_tk_init, "1") == 0) {
        return TCL_OK;
    }

#ifdef TKINTER_PROTECT_LOADTK
    if (tk_load_failed) {
        PySys_WriteStderr("Tk_Init error: %s\n", TKINTER_LOADTK_ERRMSG);
        return TCL_ERROR;
    }
#endif

    if (Tk_Init(interp) == TCL_ERROR) {
#ifdef TKINTER_PROTECT_LOADTK
        tk_load_failed = 1;
#endif
        PySys_WriteStderr("Tk_Init error: %s\n", Tcl_GetStringResult(interp));
        return TCL_ERROR;
    }

    return TCL_OK;
}
#endif /* !WITH_APPINIT */




/* Initialize the Tk application; see the `main' function in
 * `tkMain.c'.
 */

static void EnableEventHook(void); /* Forward */
static void DisableEventHook(void); /* Forward */

static TkappObject *
Tkapp_New(char *screenName, char *className,
          int interactive, int wantobjects, int wantTk, int sync, char *use)
{
    TkappObject *v;
    char *argv0;

    v = PyObject_New(TkappObject, (PyTypeObject *) Tkapp_Type);
    if (v == NULL)
        return NULL;
    Py_INCREF(Tkapp_Type);

    v->interp = Tcl_CreateInterp();
    v->wantobjects = wantobjects;
    v->threaded = Tcl_GetVar2Ex(v->interp, "tcl_platform", "threaded",
                                TCL_GLOBAL_ONLY) != NULL;
    v->thread_id = Tcl_GetCurrentThread();
    v->dispatching = 0;

#ifndef TCL_THREADS
    if (v->threaded) {
        PyErr_SetString(PyExc_RuntimeError,
                        "Tcl is threaded but _tkinter is not");
        Py_DECREF(v);
        return 0;
    }
#endif
#ifdef WITH_THREAD
    if (v->threaded && tcl_lock) {
        /* If Tcl is threaded, we don't need the lock. */
        PyThread_free_lock(tcl_lock);
        tcl_lock = NULL;
    }
#endif

    v->BooleanType = Tcl_GetObjType("boolean");
    v->ByteArrayType = Tcl_GetObjType("bytearray");
    v->DoubleType = Tcl_GetObjType("double");
    v->IntType = Tcl_GetObjType("int");
    v->ListType = Tcl_GetObjType("list");
    v->ProcBodyType = Tcl_GetObjType("procbody");
    v->StringType = Tcl_GetObjType("string");

    /* Delete the 'exit' command, which can screw things up */
    Tcl_DeleteCommand(v->interp, "exit");

    if (screenName != NULL)
        Tcl_SetVar2(v->interp, "env", "DISPLAY",
                    screenName, TCL_GLOBAL_ONLY);

    if (interactive)
        Tcl_SetVar(v->interp, "tcl_interactive", "1", TCL_GLOBAL_ONLY);
    else
        Tcl_SetVar(v->interp, "tcl_interactive", "0", TCL_GLOBAL_ONLY);

    /* This is used to get the application class for Tk 4.1 and up */
    argv0 = (char*)ckalloc(strlen(className) + 1);
    if (!argv0) {
        PyErr_NoMemory();
        Py_DECREF(v);
        return NULL;
    }

    strcpy(argv0, className);
    if (Py_ISUPPER(Py_CHARMASK(argv0[0])))
        argv0[0] = Py_TOLOWER(Py_CHARMASK(argv0[0]));
    Tcl_SetVar(v->interp, "argv0", argv0, TCL_GLOBAL_ONLY);
    ckfree(argv0);

    if (! wantTk) {
        Tcl_SetVar(v->interp,
                        "_tkinter_skip_tk_init", "1", TCL_GLOBAL_ONLY);
    }
#ifdef TKINTER_PROTECT_LOADTK
    else if (tk_load_failed) {
        Tcl_SetVar(v->interp,
                        "_tkinter_tk_failed", "1", TCL_GLOBAL_ONLY);
    }
#endif

    /* some initial arguments need to be in argv */
    if (sync || use) {
        char *args;
        int len = 0;

        if (sync)
            len += sizeof "-sync";
        if (use)
            len += strlen(use) + sizeof "-use ";

        args = (char*)ckalloc(len);
        if (!args) {
            PyErr_NoMemory();
            Py_DECREF(v);
            return NULL;
        }

        args[0] = '\0';
        if (sync)
            strcat(args, "-sync");
        if (use) {
            if (sync)
                strcat(args, " ");
            strcat(args, "-use ");
            strcat(args, use);
        }

        Tcl_SetVar(v->interp, "argv", args, TCL_GLOBAL_ONLY);
        ckfree(args);
    }

    if (Tcl_AppInit(v->interp) != TCL_OK) {
        PyObject *result = Tkinter_Error((PyObject *)v);
#ifdef TKINTER_PROTECT_LOADTK
        if (wantTk) {
            const char *_tkinter_tk_failed;
            _tkinter_tk_failed = Tcl_GetVar(v->interp,
                            "_tkinter_tk_failed", TCL_GLOBAL_ONLY);

            if ( _tkinter_tk_failed != NULL &&
                            strcmp(_tkinter_tk_failed, "1") == 0) {
                tk_load_failed = 1;
            }
        }
#endif
        Py_DECREF((PyObject *)v);
        return (TkappObject *)result;
    }

    EnableEventHook();

    return v;
}


#ifdef WITH_THREAD
static void
Tkapp_ThreadSend(TkappObject *self, Tcl_Event *ev,
                 Tcl_Condition *cond, Tcl_Mutex *mutex)
{
    Py_BEGIN_ALLOW_THREADS;
    Tcl_MutexLock(mutex);
    Tcl_ThreadQueueEvent(self->thread_id, ev, TCL_QUEUE_TAIL);
    Tcl_ThreadAlert(self->thread_id);
    Tcl_ConditionWait(cond, mutex, NULL);
    Tcl_MutexUnlock(mutex);
    Py_END_ALLOW_THREADS
}
#endif


/** Tcl Eval **/

typedef struct {
    PyObject_HEAD
    Tcl_Obj *value;
    PyObject *string; /* This cannot cause cycles. */
} PyTclObject;

static PyObject *PyTclObject_Type;
#define PyTclObject_Check(v) ((v)->ob_type == (PyTypeObject *) PyTclObject_Type)

static PyObject *
newPyTclObject(Tcl_Obj *arg)
{
    PyTclObject *self;
    self = PyObject_New(PyTclObject, (PyTypeObject *) PyTclObject_Type);
    if (self == NULL)
        return NULL;
    Py_INCREF(PyTclObject_Type);
    Tcl_IncrRefCount(arg);
    self->value = arg;
    self->string = NULL;
    return (PyObject*)self;
}

static void
PyTclObject_dealloc(PyTclObject *self)
{
    PyObject *tp = (PyObject *) Py_TYPE(self);
    Tcl_DecrRefCount(self->value);
    Py_XDECREF(self->string);
    PyObject_Del(self);
    Py_DECREF(tp);
}

static char*
PyTclObject_TclString(PyObject *self)
{
    return Tcl_GetString(((PyTclObject*)self)->value);
}

/* Like _str, but create Unicode if necessary. */
PyDoc_STRVAR(PyTclObject_string__doc__,
"the string representation of this object, either as str or bytes");

static PyObject *
PyTclObject_string(PyTclObject *self, void *ignored)
{
    if (!self->string) {
        self->string = unicodeFromTclObj(self->value);
        if (!self->string)
            return NULL;
    }
    Py_INCREF(self->string);
    return self->string;
}

static PyObject *
PyTclObject_str(PyTclObject *self, void *ignored)
{
    if (self->string) {
        Py_INCREF(self->string);
        return self->string;
    }
    /* XXX Could chache result if it is non-ASCII. */
    return unicodeFromTclObj(self->value);
}

static PyObject *
PyTclObject_repr(PyTclObject *self)
{
    PyObject *repr, *str = PyTclObject_str(self, NULL);
    if (str == NULL)
        return NULL;
    repr = PyUnicode_FromFormat("<%s object: %R>",
                                self->value->typePtr->name, str);
    Py_DECREF(str);
    return repr;
}

#define TEST_COND(cond) ((cond) ? Py_True : Py_False)

static PyObject *
PyTclObject_richcompare(PyObject *self, PyObject *other, int op)
{
    int result;
    PyObject *v;

    /* neither argument should be NULL, unless something's gone wrong */
    if (self == NULL || other == NULL) {
        PyErr_BadInternalCall();
        return NULL;
    }

    /* both arguments should be instances of PyTclObject */
    if (!PyTclObject_Check(self) || !PyTclObject_Check(other)) {
        v = Py_NotImplemented;
        goto finished;
    }

    if (self == other)
        /* fast path when self and other are identical */
        result = 0;
    else
        result = strcmp(Tcl_GetString(((PyTclObject *)self)->value),
                        Tcl_GetString(((PyTclObject *)other)->value));
    /* Convert return value to a Boolean */
    switch (op) {
    case Py_EQ:
        v = TEST_COND(result == 0);
        break;
    case Py_NE:
        v = TEST_COND(result != 0);
        break;
    case Py_LE:
        v = TEST_COND(result <= 0);
        break;
    case Py_GE:
        v = TEST_COND(result >= 0);
        break;
    case Py_LT:
        v = TEST_COND(result < 0);
        break;
    case Py_GT:
        v = TEST_COND(result > 0);
        break;
    default:
        PyErr_BadArgument();
        return NULL;
    }
  finished:
    Py_INCREF(v);
    return v;
}

PyDoc_STRVAR(get_typename__doc__, "name of the Tcl type");

static PyObject*
get_typename(PyTclObject* obj, void* ignored)
{
    return unicodeFromTclString(obj->value->typePtr->name);
}


static PyGetSetDef PyTclObject_getsetlist[] = {
    {"typename", (getter)get_typename, NULL, get_typename__doc__},
    {"string", (getter)PyTclObject_string, NULL,
     PyTclObject_string__doc__},
    {0},
};

static PyType_Slot PyTclObject_Type_slots[] = {
    {Py_tp_dealloc, (destructor)PyTclObject_dealloc},
    {Py_tp_repr, (reprfunc)PyTclObject_repr},
    {Py_tp_str, (reprfunc)PyTclObject_str},
    {Py_tp_getattro, PyObject_GenericGetAttr},
    {Py_tp_richcompare, PyTclObject_richcompare},
    {Py_tp_getset, PyTclObject_getsetlist},
    {0, 0}
};

static PyType_Spec PyTclObject_Type_spec = {
    "_tkinter.Tcl_Obj",
    sizeof(PyTclObject),
    0,
    Py_TPFLAGS_DEFAULT,
    PyTclObject_Type_slots,
};


#if PY_SIZE_MAX > INT_MAX
#define CHECK_STRING_LENGTH(s) do {                                     \
        if (s != NULL && strlen(s) >= INT_MAX) {                        \
            PyErr_SetString(PyExc_OverflowError, "string is too long"); \
            return NULL;                                                \
        } } while(0)
#else
#define CHECK_STRING_LENGTH(s)
#endif

static Tcl_Obj*
AsObj(PyObject *value)
{
    Tcl_Obj *result;
    long longVal;
    int overflow;

    if (PyBytes_Check(value))
        return Tcl_NewByteArrayObj((unsigned char *)PyBytes_AS_STRING(value),
                                   PyBytes_GET_SIZE(value));
    else if (PyBool_Check(value))
        return Tcl_NewBooleanObj(PyObject_IsTrue(value));
    else if (PyLong_CheckExact(value) &&
             ((longVal = PyLong_AsLongAndOverflow(value, &overflow)),
              !overflow)) {
        /* If there is an overflow in the long conversion,
           fall through to default object handling. */
        return Tcl_NewLongObj(longVal);
    }
    else if (PyFloat_Check(value))
        return Tcl_NewDoubleObj(PyFloat_AS_DOUBLE(value));
    else if (PyTuple_Check(value)) {
        Tcl_Obj **argv;
        Py_ssize_t size, i;

        size = PyTuple_Size(value);
        if (!CHECK_SIZE(size, sizeof(Tcl_Obj *))) {
            PyErr_SetString(PyExc_OverflowError, "tuple is too long");
            return NULL;
        }
        argv = (Tcl_Obj **) ckalloc(((size_t)size) * sizeof(Tcl_Obj *));
        if(!argv)
          return 0;
        for (i = 0; i < size; i++)
          argv[i] = AsObj(PyTuple_GetItem(value,i));
        result = Tcl_NewListObj(PyTuple_Size(value), argv);
        ckfree(FREECAST argv);
        return result;
    }
    else if (PyUnicode_Check(value)) {
        void *inbuf;
        Py_ssize_t size;
        int kind;
        Tcl_UniChar *outbuf = NULL;
        Py_ssize_t i;
        size_t allocsize;

        if (PyUnicode_READY(value) == -1)
            return NULL;

        inbuf = PyUnicode_DATA(value);
        size = PyUnicode_GET_LENGTH(value);
        if (!CHECK_SIZE(size, sizeof(Tcl_UniChar))) {
            PyErr_SetString(PyExc_OverflowError, "string is too long");
            return NULL;
        }
        kind = PyUnicode_KIND(value);
        if (kind == sizeof(Tcl_UniChar))
            return Tcl_NewUnicodeObj(inbuf, size);
        allocsize = ((size_t)size) * sizeof(Tcl_UniChar);
        outbuf = (Tcl_UniChar*)ckalloc(allocsize);
        /* Else overflow occurred, and we take the next exit */
        if (!outbuf) {
            PyErr_NoMemory();
            return NULL;
        }
        for (i = 0; i < size; i++) {
            Py_UCS4 ch = PyUnicode_READ(kind, inbuf, i);
            /* We cannot test for sizeof(Tcl_UniChar) directly,
               so we test for UTF-8 size instead. */
#if TCL_UTF_MAX == 3
            if (ch >= 0x10000) {
                /* Tcl doesn't do UTF-16, yet. */
                PyErr_Format(Tkinter_TclError,
                             "character U+%x is above the range "
                             "(U+0000-U+FFFF) allowed by Tcl",
                             ch);
                ckfree(FREECAST outbuf);
                return NULL;
            }
#endif
            outbuf[i] = ch;
        }
        result = Tcl_NewUnicodeObj(outbuf, size);
        ckfree(FREECAST outbuf);
        return result;
    }
    else if(PyTclObject_Check(value)) {
        Tcl_Obj *v = ((PyTclObject*)value)->value;
        Tcl_IncrRefCount(v);
        return v;
    }
    else {
        PyObject *v = PyObject_Str(value);
        if (!v)
            return 0;
        result = AsObj(v);
        Py_DECREF(v);
        return result;
    }
}

static PyObject*
FromObj(PyObject* tkapp, Tcl_Obj *value)
{
    PyObject *result = NULL;
    TkappObject *app = (TkappObject*)tkapp;

    if (value->typePtr == NULL) {
        return unicodeFromTclStringAndSize(value->bytes, value->length);
    }

    if (value->typePtr == app->BooleanType) {
        result = value->internalRep.longValue ? Py_True : Py_False;
        Py_INCREF(result);
        return result;
    }

    if (value->typePtr == app->ByteArrayType) {
        int size;
        char *data = (char*)Tcl_GetByteArrayFromObj(value, &size);
        return PyBytes_FromStringAndSize(data, size);
    }

    if (value->typePtr == app->DoubleType) {
        return PyFloat_FromDouble(value->internalRep.doubleValue);
    }

    if (value->typePtr == app->IntType) {
        return PyLong_FromLong(value->internalRep.longValue);
    }

    if (value->typePtr == app->ListType) {
        int size;
        int i, status;
        PyObject *elem;
        Tcl_Obj *tcl_elem;

        status = Tcl_ListObjLength(Tkapp_Interp(tkapp), value, &size);
        if (status == TCL_ERROR)
            return Tkinter_Error(tkapp);
        result = PyTuple_New(size);
        if (!result)
            return NULL;
        for (i = 0; i < size; i++) {
            status = Tcl_ListObjIndex(Tkapp_Interp(tkapp),
                                      value, i, &tcl_elem);
            if (status == TCL_ERROR) {
                Py_DECREF(result);
                return Tkinter_Error(tkapp);
            }
            elem = FromObj(tkapp, tcl_elem);
            if (!elem) {
                Py_DECREF(result);
                return NULL;
            }
            PyTuple_SetItem(result, i, elem);
        }
        return result;
    }

    if (value->typePtr == app->ProcBodyType) {
      /* fall through: return tcl object. */
    }

    if (value->typePtr == app->StringType) {
        return PyUnicode_FromKindAndData(
            sizeof(Tcl_UniChar), Tcl_GetUnicode(value),
            Tcl_GetCharLength(value));
    }

    return newPyTclObject(value);
}

#ifdef WITH_THREAD
/* This mutex synchronizes inter-thread command calls. */
TCL_DECLARE_MUTEX(call_mutex)

typedef struct Tkapp_CallEvent {
    Tcl_Event ev;            /* Must be first */
    TkappObject *self;
    PyObject *args;
    int flags;
    PyObject **res;
    PyObject **exc_type, **exc_value, **exc_tb;
    Tcl_Condition *done;
} Tkapp_CallEvent;
#endif

void
Tkapp_CallDeallocArgs(Tcl_Obj** objv, Tcl_Obj** objStore, int objc)
{
    int i;
    for (i = 0; i < objc; i++)
        Tcl_DecrRefCount(objv[i]);
    if (objv != objStore)
        ckfree(FREECAST objv);
}

/* Convert Python objects to Tcl objects. This must happen in the
   interpreter thread, which may or may not be the calling thread. */

static Tcl_Obj**
Tkapp_CallArgs(PyObject *args, Tcl_Obj** objStore, int *pobjc)
{
    Tcl_Obj **objv = objStore;
    Py_ssize_t objc = 0, i;
    if (args == NULL)
        /* do nothing */;

    else if (!PyTuple_Check(args)) {
        objv[0] = AsObj(args);
        if (objv[0] == 0)
            goto finally;
        objc = 1;
        Tcl_IncrRefCount(objv[0]);
    }
    else {
        objc = PyTuple_Size(args);

        if (objc > ARGSZ) {
            if (!CHECK_SIZE(objc, sizeof(Tcl_Obj *))) {
                PyErr_SetString(PyExc_OverflowError, "tuple is too long");
                return NULL;
            }
            objv = (Tcl_Obj **)ckalloc(((size_t)objc) * sizeof(Tcl_Obj *));
            if (objv == NULL) {
                PyErr_NoMemory();
                objc = 0;
                goto finally;
            }
        }

        for (i = 0; i < objc; i++) {
            PyObject *v = PyTuple_GetItem(args, i);
            if (v == Py_None) {
                objc = i;
                break;
            }
            objv[i] = AsObj(v);
            if (!objv[i]) {
                /* Reset objc, so it attempts to clear
                   objects only up to i. */
                objc = i;
                goto finally;
            }
            Tcl_IncrRefCount(objv[i]);
        }
    }
    *pobjc = objc;
    return objv;
finally:
    Tkapp_CallDeallocArgs(objv, objStore, objc);
    return NULL;
}

/* Convert the results of a command call into a Python objects. */

static PyObject*
Tkapp_CallResult(TkappObject *self)
{
    PyObject *res = NULL;
    Tcl_Obj *value = Tcl_GetObjResult(self->interp);
    if(self->wantobjects) {
        /* Not sure whether the IncrRef is necessary, but something
           may overwrite the interpreter result while we are
           converting it. */
        Tcl_IncrRefCount(value);
        res = FromObj((PyObject*)self, value);
        Tcl_DecrRefCount(value);
    } else {
        res = unicodeFromTclObj(value);
    }
    return res;
}

#ifdef WITH_THREAD

/* Tkapp_CallProc is the event procedure that is executed in the context of
   the Tcl interpreter thread. Initially, it holds the Tcl lock, and doesn't
   hold the Python lock. */

static int
Tkapp_CallProc(Tkapp_CallEvent *e, int flags)
{
    Tcl_Obj *objStore[ARGSZ];
    Tcl_Obj **objv;
    int objc;
    int i;
    ENTER_PYTHON
    objv = Tkapp_CallArgs(e->args, objStore, &objc);
    if (!objv) {
        PyErr_Fetch(e->exc_type, e->exc_value, e->exc_tb);
        *(e->res) = NULL;
    }
    LEAVE_PYTHON
    if (!objv)
        goto done;
    i = Tcl_EvalObjv(e->self->interp, objc, objv, e->flags);
    ENTER_PYTHON
    if (i == TCL_ERROR) {
        *(e->res) = NULL;
        *(e->exc_type) = NULL;
        *(e->exc_tb) = NULL;
        *(e->exc_value) = PyObject_CallFunction(
            Tkinter_TclError, "s",
            Tcl_GetStringResult(e->self->interp));
    }
    else {
        *(e->res) = Tkapp_CallResult(e->self);
    }
    LEAVE_PYTHON

    Tkapp_CallDeallocArgs(objv, objStore, objc);
done:
    /* Wake up calling thread. */
    Tcl_MutexLock(&call_mutex);
    Tcl_ConditionNotify(e->done);
    Tcl_MutexUnlock(&call_mutex);
    return 1;
}

#endif

/* This is the main entry point for calling a Tcl command.
   It supports three cases, with regard to threading:
   1. Tcl is not threaded: Must have the Tcl lock, then can invoke command in
      the context of the calling thread.
   2. Tcl is threaded, caller of the command is in the interpreter thread:
      Execute the command in the calling thread. Since the Tcl lock will
      not be used, we can merge that with case 1.
   3. Tcl is threaded, caller is in a different thread: Must queue an event to
      the interpreter thread. Allocation of Tcl objects needs to occur in the
      interpreter thread, so we ship the PyObject* args to the target thread,
      and perform processing there. */

static PyObject *
Tkapp_Call(PyObject *selfptr, PyObject *args)
{
    Tcl_Obj *objStore[ARGSZ];
    Tcl_Obj **objv = NULL;
    int objc, i;
    PyObject *res = NULL;
    TkappObject *self = (TkappObject*)selfptr;
    int flags = TCL_EVAL_DIRECT | TCL_EVAL_GLOBAL;

    /* If args is a single tuple, replace with contents of tuple */
    if (1 == PyTuple_Size(args)){
        PyObject* item = PyTuple_GetItem(args, 0);
        if (PyTuple_Check(item))
            args = item;
    }
#ifdef WITH_THREAD
    if (self->threaded && self->thread_id != Tcl_GetCurrentThread()) {
        /* We cannot call the command directly. Instead, we must
           marshal the parameters to the interpreter thread. */
        Tkapp_CallEvent *ev;
        Tcl_Condition cond = NULL;
        PyObject *exc_type, *exc_value, *exc_tb;
        if (!WaitForMainloop(self))
            return NULL;
        ev = (Tkapp_CallEvent*)ckalloc(sizeof(Tkapp_CallEvent));
        ev->ev.proc = (Tcl_EventProc*)Tkapp_CallProc;
        ev->self = self;
        ev->args = args;
        ev->res = &res;
        ev->exc_type = &exc_type;
        ev->exc_value = &exc_value;
        ev->exc_tb = &exc_tb;
        ev->done = &cond;

        Tkapp_ThreadSend(self, (Tcl_Event*)ev, &cond, &call_mutex);

        if (res == NULL) {
            if (exc_type)
                PyErr_Restore(exc_type, exc_value, exc_tb);
            else
                PyErr_SetObject(Tkinter_TclError, exc_value);
        }
        Tcl_ConditionFinalize(&cond);
    }
    else
#endif
    {

        objv = Tkapp_CallArgs(args, objStore, &objc);
        if (!objv)
            return NULL;

        ENTER_TCL

        i = Tcl_EvalObjv(self->interp, objc, objv, flags);

        ENTER_OVERLAP

        if (i == TCL_ERROR)
            Tkinter_Error(selfptr);
        else
            res = Tkapp_CallResult(self);

        LEAVE_OVERLAP_TCL

        Tkapp_CallDeallocArgs(objv, objStore, objc);
    }
    return res;
}


static PyObject *
Tkapp_Eval(PyObject *self, PyObject *args)
{
    char *script;
    PyObject *res = NULL;
    int err;

    if (!PyArg_ParseTuple(args, "s:eval", &script))
        return NULL;

    CHECK_STRING_LENGTH(script);
    CHECK_TCL_APPARTMENT;

    ENTER_TCL
    err = Tcl_Eval(Tkapp_Interp(self), script);
    ENTER_OVERLAP
    if (err == TCL_ERROR)
        res = Tkinter_Error(self);
    else
        res = unicodeFromTclString(Tkapp_Result(self));
    LEAVE_OVERLAP_TCL
    return res;
}

static PyObject *
Tkapp_EvalFile(PyObject *self, PyObject *args)
{
    char *fileName;
    PyObject *res = NULL;
    int err;

    if (!PyArg_ParseTuple(args, "s:evalfile", &fileName))
        return NULL;

    CHECK_STRING_LENGTH(fileName);
    CHECK_TCL_APPARTMENT;

    ENTER_TCL
    err = Tcl_EvalFile(Tkapp_Interp(self), fileName);
    ENTER_OVERLAP
    if (err == TCL_ERROR)
        res = Tkinter_Error(self);
    else
        res = unicodeFromTclString(Tkapp_Result(self));
    LEAVE_OVERLAP_TCL
    return res;
}

static PyObject *
Tkapp_Record(PyObject *self, PyObject *args)
{
    char *script;
    PyObject *res = NULL;
    int err;

    if (!PyArg_ParseTuple(args, "s:record", &script))
        return NULL;

    CHECK_STRING_LENGTH(script);
    CHECK_TCL_APPARTMENT;

    ENTER_TCL
    err = Tcl_RecordAndEval(Tkapp_Interp(self), script, TCL_NO_EVAL);
    ENTER_OVERLAP
    if (err == TCL_ERROR)
        res = Tkinter_Error(self);
    else
        res = unicodeFromTclString(Tkapp_Result(self));
    LEAVE_OVERLAP_TCL
    return res;
}

static PyObject *
Tkapp_AddErrorInfo(PyObject *self, PyObject *args)
{
    char *msg;

    if (!PyArg_ParseTuple(args, "s:adderrorinfo", &msg))
        return NULL;
    CHECK_STRING_LENGTH(msg);
    CHECK_TCL_APPARTMENT;

    ENTER_TCL
    Tcl_AddErrorInfo(Tkapp_Interp(self), msg);
    LEAVE_TCL

    Py_RETURN_NONE;
}



/** Tcl Variable **/

typedef PyObject* (*EventFunc)(PyObject*, PyObject *args, int flags);

#ifdef WITH_THREAD
TCL_DECLARE_MUTEX(var_mutex)

typedef struct VarEvent {
    Tcl_Event ev; /* must be first */
    PyObject *self;
    PyObject *args;
    int flags;
    EventFunc func;
    PyObject **res;
    PyObject **exc_type;
    PyObject **exc_val;
    Tcl_Condition *cond;
} VarEvent;
#endif

static int
varname_converter(PyObject *in, void *_out)
{
    char *s;
    char **out = (char**)_out;
    if (PyBytes_Check(in)) {
        if (PyBytes_Size(in) > INT_MAX) {
            PyErr_SetString(PyExc_OverflowError, "bytes object is too long");
            return 0;
        }
        s = PyBytes_AsString(in);
        if (strlen(s) != PyBytes_Size(in)) {
            PyErr_SetString(PyExc_ValueError, "null byte in bytes object");
            return 0;
        }
        *out = s;
        return 1;
    }
    if (PyUnicode_Check(in)) {
        Py_ssize_t size;
        s = PyUnicode_AsUTF8AndSize(in, &size);
        if (s == NULL) {
            return 0;
        }
        if (size > INT_MAX) {
            PyErr_SetString(PyExc_OverflowError, "string is too long");
            return 0;
        }
        if (strlen(s) != size) {
            PyErr_SetString(PyExc_ValueError, "null character in string");
            return 0;
        }
        *out = s;
        return 1;
    }
    if (PyTclObject_Check(in)) {
        *out = PyTclObject_TclString(in);
        return 1;
    }
    PyErr_Format(PyExc_TypeError,
                 "must be str, bytes or Tcl_Obj, not %.50s",
                 in->ob_type->tp_name);
    return 0;
}

#ifdef WITH_THREAD

static void
var_perform(VarEvent *ev)
{
    *(ev->res) = ev->func(ev->self, ev->args, ev->flags);
    if (!*(ev->res)) {
        PyObject *exc, *val, *tb;
        PyErr_Fetch(&exc, &val, &tb);
        PyErr_NormalizeException(&exc, &val, &tb);
        *(ev->exc_type) = exc;
        *(ev->exc_val) = val;
        Py_DECREF(tb);
    }

}

static int
var_proc(VarEvent* ev, int flags)
{
    ENTER_PYTHON
    var_perform(ev);
    Tcl_MutexLock(&var_mutex);
    Tcl_ConditionNotify(ev->cond);
    Tcl_MutexUnlock(&var_mutex);
    LEAVE_PYTHON
    return 1;
}

#endif

static PyObject*
var_invoke(EventFunc func, PyObject *selfptr, PyObject *args, int flags)
{
#ifdef WITH_THREAD
    TkappObject *self = (TkappObject*)selfptr;
    if (self->threaded && self->thread_id != Tcl_GetCurrentThread()) {
        TkappObject *self = (TkappObject*)selfptr;
        VarEvent *ev;
        PyObject *res, *exc_type, *exc_val;
        Tcl_Condition cond = NULL;

        /* The current thread is not the interpreter thread.  Marshal
           the call to the interpreter thread, then wait for
           completion. */
        if (!WaitForMainloop(self))
            return NULL;

        ev = (VarEvent*)ckalloc(sizeof(VarEvent));

        ev->self = selfptr;
        ev->args = args;
        ev->flags = flags;
        ev->func = func;
        ev->res = &res;
        ev->exc_type = &exc_type;
        ev->exc_val = &exc_val;
        ev->cond = &cond;
        ev->ev.proc = (Tcl_EventProc*)var_proc;
        Tkapp_ThreadSend(self, (Tcl_Event*)ev, &cond, &var_mutex);
        Tcl_ConditionFinalize(&cond);
        if (!res) {
            PyErr_SetObject(exc_type, exc_val);
            Py_DECREF(exc_type);
            Py_DECREF(exc_val);
            return NULL;
        }
        return res;
    }
#endif
    /* Tcl is not threaded, or this is the interpreter thread. */
    return func(selfptr, args, flags);
}

static PyObject *
SetVar(PyObject *self, PyObject *args, int flags)
{
    char *name1, *name2;
    PyObject *newValue;
    PyObject *res = NULL;
    Tcl_Obj *newval, *ok;

    switch (PyTuple_GET_SIZE(args)) {
    case 2:
        if (!PyArg_ParseTuple(args, "O&O:setvar",
                              varname_converter, &name1, &newValue))
            return NULL;
        /* XXX Acquire tcl lock??? */
        newval = AsObj(newValue);
        if (newval == NULL)
            return NULL;
        ENTER_TCL
        ok = Tcl_SetVar2Ex(Tkapp_Interp(self), name1, NULL,
                           newval, flags);
        ENTER_OVERLAP
        if (!ok)
            Tkinter_Error(self);
        else {
            res = Py_None;
            Py_INCREF(res);
        }
        LEAVE_OVERLAP_TCL
        break;
    case 3:
        if (!PyArg_ParseTuple(args, "ssO:setvar",
                              &name1, &name2, &newValue))
            return NULL;
        CHECK_STRING_LENGTH(name1);
        CHECK_STRING_LENGTH(name2);
        /* XXX must hold tcl lock already??? */
        newval = AsObj(newValue);
        ENTER_TCL
        ok = Tcl_SetVar2Ex(Tkapp_Interp(self), name1, name2, newval, flags);
        ENTER_OVERLAP
        if (!ok)
            Tkinter_Error(self);
        else {
            res = Py_None;
            Py_INCREF(res);
        }
        LEAVE_OVERLAP_TCL
        break;
    default:
        PyErr_SetString(PyExc_TypeError, "setvar requires 2 to 3 arguments");
        return NULL;
    }
    return res;
}

static PyObject *
Tkapp_SetVar(PyObject *self, PyObject *args)
{
    return var_invoke(SetVar, self, args, TCL_LEAVE_ERR_MSG);
}

static PyObject *
Tkapp_GlobalSetVar(PyObject *self, PyObject *args)
{
    return var_invoke(SetVar, self, args, TCL_LEAVE_ERR_MSG | TCL_GLOBAL_ONLY);
}



static PyObject *
GetVar(PyObject *self, PyObject *args, int flags)
{
    char *name1, *name2=NULL;
    PyObject *res = NULL;
    Tcl_Obj *tres;

    if (!PyArg_ParseTuple(args, "O&|s:getvar",
                          varname_converter, &name1, &name2))
        return NULL;

    CHECK_STRING_LENGTH(name2);
    ENTER_TCL
    tres = Tcl_GetVar2Ex(Tkapp_Interp(self), name1, name2, flags);
    ENTER_OVERLAP
    if (tres == NULL) {
        PyErr_SetString(Tkinter_TclError,
                        Tcl_GetStringResult(Tkapp_Interp(self)));
    } else {
        if (((TkappObject*)self)->wantobjects) {
            res = FromObj(self, tres);
        }
        else {
            res = unicodeFromTclObj(tres);
        }
    }
    LEAVE_OVERLAP_TCL
    return res;
}

static PyObject *
Tkapp_GetVar(PyObject *self, PyObject *args)
{
    return var_invoke(GetVar, self, args, TCL_LEAVE_ERR_MSG);
}

static PyObject *
Tkapp_GlobalGetVar(PyObject *self, PyObject *args)
{
    return var_invoke(GetVar, self, args, TCL_LEAVE_ERR_MSG | TCL_GLOBAL_ONLY);
}



static PyObject *
UnsetVar(PyObject *self, PyObject *args, int flags)
{
    char *name1, *name2=NULL;
    int code;
    PyObject *res = NULL;

    if (!PyArg_ParseTuple(args, "s|s:unsetvar", &name1, &name2))
        return NULL;

    CHECK_STRING_LENGTH(name1);
    CHECK_STRING_LENGTH(name2);
    ENTER_TCL
    code = Tcl_UnsetVar2(Tkapp_Interp(self), name1, name2, flags);
    ENTER_OVERLAP
    if (code == TCL_ERROR)
        res = Tkinter_Error(self);
    else {
        Py_INCREF(Py_None);
        res = Py_None;
    }
    LEAVE_OVERLAP_TCL
    return res;
}

static PyObject *
Tkapp_UnsetVar(PyObject *self, PyObject *args)
{
    return var_invoke(UnsetVar, self, args, TCL_LEAVE_ERR_MSG);
}

static PyObject *
Tkapp_GlobalUnsetVar(PyObject *self, PyObject *args)
{
    return var_invoke(UnsetVar, self, args,
                      TCL_LEAVE_ERR_MSG | TCL_GLOBAL_ONLY);
}



/** Tcl to Python **/

static PyObject *
Tkapp_GetInt(PyObject *self, PyObject *args)
{
    char *s;
    int v;

    if (PyTuple_Size(args) == 1) {
        PyObject* o = PyTuple_GetItem(args, 0);
        if (PyLong_Check(o)) {
            Py_INCREF(o);
            return o;
        }
    }
    if (!PyArg_ParseTuple(args, "s:getint", &s))
        return NULL;
    CHECK_STRING_LENGTH(s);
    if (Tcl_GetInt(Tkapp_Interp(self), s, &v) == TCL_ERROR)
        return Tkinter_Error(self);
    return Py_BuildValue("i", v);
}

static PyObject *
Tkapp_GetDouble(PyObject *self, PyObject *args)
{
    char *s;
    double v;

    if (PyTuple_Size(args) == 1) {
        PyObject *o = PyTuple_GetItem(args, 0);
        if (PyFloat_Check(o)) {
            Py_INCREF(o);
            return o;
        }
    }
    if (!PyArg_ParseTuple(args, "s:getdouble", &s))
        return NULL;
    CHECK_STRING_LENGTH(s);
    if (Tcl_GetDouble(Tkapp_Interp(self), s, &v) == TCL_ERROR)
        return Tkinter_Error(self);
    return Py_BuildValue("d", v);
}

static PyObject *
Tkapp_GetBoolean(PyObject *self, PyObject *args)
{
    char *s;
    int v;

    if (PyTuple_Size(args) == 1) {
        PyObject *o = PyTuple_GetItem(args, 0);
        if (PyLong_Check(o)) {
            Py_INCREF(o);
            return o;
        }
    }
    if (!PyArg_ParseTuple(args, "s:getboolean", &s))
        return NULL;
    CHECK_STRING_LENGTH(s);
    if (Tcl_GetBoolean(Tkapp_Interp(self), s, &v) == TCL_ERROR)
        return Tkinter_Error(self);
    return PyBool_FromLong(v);
}

static PyObject *
Tkapp_ExprString(PyObject *self, PyObject *args)
{
    char *s;
    PyObject *res = NULL;
    int retval;

    if (!PyArg_ParseTuple(args, "s:exprstring", &s))
        return NULL;

    CHECK_STRING_LENGTH(s);
    CHECK_TCL_APPARTMENT;

    ENTER_TCL
    retval = Tcl_ExprString(Tkapp_Interp(self), s);
    ENTER_OVERLAP
    if (retval == TCL_ERROR)
        res = Tkinter_Error(self);
    else
        res = unicodeFromTclString(Tkapp_Result(self));
    LEAVE_OVERLAP_TCL
    return res;
}

static PyObject *
Tkapp_ExprLong(PyObject *self, PyObject *args)
{
    char *s;
    PyObject *res = NULL;
    int retval;
    long v;

    if (!PyArg_ParseTuple(args, "s:exprlong", &s))
        return NULL;

    CHECK_STRING_LENGTH(s);
    CHECK_TCL_APPARTMENT;

    ENTER_TCL
    retval = Tcl_ExprLong(Tkapp_Interp(self), s, &v);
    ENTER_OVERLAP
    if (retval == TCL_ERROR)
        res = Tkinter_Error(self);
    else
        res = Py_BuildValue("l", v);
    LEAVE_OVERLAP_TCL
    return res;
}

static PyObject *
Tkapp_ExprDouble(PyObject *self, PyObject *args)
{
    char *s;
    PyObject *res = NULL;
    double v;
    int retval;

    if (!PyArg_ParseTuple(args, "s:exprdouble", &s))
        return NULL;
    CHECK_STRING_LENGTH(s);
    CHECK_TCL_APPARTMENT;
    PyFPE_START_PROTECT("Tkapp_ExprDouble", return 0)
    ENTER_TCL
    retval = Tcl_ExprDouble(Tkapp_Interp(self), s, &v);
    ENTER_OVERLAP
    PyFPE_END_PROTECT(retval)
    if (retval == TCL_ERROR)
        res = Tkinter_Error(self);
    else
        res = Py_BuildValue("d", v);
    LEAVE_OVERLAP_TCL
    return res;
}

static PyObject *
Tkapp_ExprBoolean(PyObject *self, PyObject *args)
{
    char *s;
    PyObject *res = NULL;
    int retval;
    int v;

    if (!PyArg_ParseTuple(args, "s:exprboolean", &s))
        return NULL;
    CHECK_STRING_LENGTH(s);
    CHECK_TCL_APPARTMENT;
    ENTER_TCL
    retval = Tcl_ExprBoolean(Tkapp_Interp(self), s, &v);
    ENTER_OVERLAP
    if (retval == TCL_ERROR)
        res = Tkinter_Error(self);
    else
        res = Py_BuildValue("i", v);
    LEAVE_OVERLAP_TCL
    return res;
}



static PyObject *
Tkapp_SplitList(PyObject *self, PyObject *args)
{
    char *list;
    int argc;
    char **argv;
    PyObject *arg, *v;
    int i;

    if (!PyArg_ParseTuple(args, "O:splitlist", &arg))
        return NULL;
    if (PyTclObject_Check(arg)) {
        int objc;
        Tcl_Obj **objv;
        if (Tcl_ListObjGetElements(Tkapp_Interp(self),
                                   ((PyTclObject*)arg)->value,
                                   &objc, &objv) == TCL_ERROR) {
            return Tkinter_Error(self);
        }
        if (!(v = PyTuple_New(objc)))
            return NULL;
        for (i = 0; i < objc; i++) {
            PyObject *s = FromObj(self, objv[i]);
            if (!s || PyTuple_SetItem(v, i, s)) {
                Py_DECREF(v);
                return NULL;
            }
        }
        return v;
    }
    if (PyTuple_Check(arg)) {
        Py_INCREF(arg);
        return arg;
    }

    if (!PyArg_ParseTuple(args, "et:splitlist", "utf-8", &list))
        return NULL;

    CHECK_STRING_LENGTH(list);
    if (Tcl_SplitList(Tkapp_Interp(self), list,
                      &argc, &argv) == TCL_ERROR)  {
        PyMem_Free(list);
        return Tkinter_Error(self);
    }

    if (!(v = PyTuple_New(argc)))
        goto finally;

    for (i = 0; i < argc; i++) {
        PyObject *s = unicodeFromTclString(argv[i]);
        if (!s || PyTuple_SetItem(v, i, s)) {
            Py_DECREF(v);
            v = NULL;
            goto finally;
        }
    }

  finally:
    ckfree(FREECAST argv);
    PyMem_Free(list);
    return v;
}

static PyObject *
Tkapp_Split(PyObject *self, PyObject *args)
{
    PyObject *arg, *v;
    char *list;

    if (!PyArg_ParseTuple(args, "O:split", &arg))
        return NULL;
    if (PyTclObject_Check(arg)) {
        Tcl_Obj *value = ((PyTclObject*)arg)->value;
        int objc;
        Tcl_Obj **objv;
        int i;
        if (Tcl_ListObjGetElements(Tkapp_Interp(self), value,
                                   &objc, &objv) == TCL_ERROR) {
            return FromObj(self, value);
        }
        if (objc == 0)
            return PyUnicode_FromString("");
        if (objc == 1)
            return FromObj(self, objv[0]);
        if (!(v = PyTuple_New(objc)))
            return NULL;
        for (i = 0; i < objc; i++) {
            PyObject *s = FromObj(self, objv[i]);
            if (!s || PyTuple_SetItem(v, i, s)) {
                Py_DECREF(v);
                return NULL;
            }
        }
        return v;
    }
    if (PyTuple_Check(arg))
        return SplitObj(arg);

    if (!PyArg_ParseTuple(args, "et:split", "utf-8", &list))
        return NULL;
    CHECK_STRING_LENGTH(list);
    v = Split(list);
    PyMem_Free(list);
    return v;
}



/** Tcl Command **/

/* Client data struct */
typedef struct {
    PyObject *self;
    PyObject *func;
} PythonCmd_ClientData;

static int
PythonCmd_Error(Tcl_Interp *interp)
{
    errorInCmd = 1;
    PyErr_Fetch(&excInCmd, &valInCmd, &trbInCmd);
    LEAVE_PYTHON
    return TCL_ERROR;
}

/* This is the Tcl command that acts as a wrapper for Python
 * function or method.
 */
static int
PythonCmd(ClientData clientData, Tcl_Interp *interp, int argc, char *argv[])
{
    PythonCmd_ClientData *data = (PythonCmd_ClientData *)clientData;
    PyObject *func, *arg, *res;
    int i, rv;
    Tcl_Obj *obj_res;

    ENTER_PYTHON

    /* TBD: no error checking here since we know, via the
     * Tkapp_CreateCommand() that the client data is a two-tuple
     */
    func = data->func;

    /* Create argument list (argv1, ..., argvN) */
    if (!(arg = PyTuple_New(argc - 1)))
        return PythonCmd_Error(interp);

    for (i = 0; i < (argc - 1); i++) {
        PyObject *s = unicodeFromTclString(argv[i + 1]);
        if (!s || PyTuple_SetItem(arg, i, s)) {
            Py_DECREF(arg);
            return PythonCmd_Error(interp);
        }
    }
    res = PyEval_CallObject(func, arg);
    Py_DECREF(arg);

    if (res == NULL)
        return PythonCmd_Error(interp);

    obj_res = AsObj(res);
    if (obj_res == NULL) {
        Py_DECREF(res);
        return PythonCmd_Error(interp);
    }
    else {
        Tcl_SetObjResult(interp, obj_res);
        rv = TCL_OK;
    }

    Py_DECREF(res);

    LEAVE_PYTHON

    return rv;
}

static void
PythonCmdDelete(ClientData clientData)
{
    PythonCmd_ClientData *data = (PythonCmd_ClientData *)clientData;

    ENTER_PYTHON
    Py_XDECREF(data->self);
    Py_XDECREF(data->func);
    PyMem_DEL(data);
    LEAVE_PYTHON
}




#ifdef WITH_THREAD
TCL_DECLARE_MUTEX(command_mutex)

typedef struct CommandEvent{
    Tcl_Event ev;
    Tcl_Interp* interp;
    char *name;
    int create;
    int *status;
    ClientData *data;
    Tcl_Condition *done;
} CommandEvent;

static int
Tkapp_CommandProc(CommandEvent *ev, int flags)
{
    if (ev->create)
        *ev->status = Tcl_CreateCommand(
            ev->interp, ev->name, PythonCmd,
            ev->data, PythonCmdDelete) == NULL;
    else
        *ev->status = Tcl_DeleteCommand(ev->interp, ev->name);
    Tcl_MutexLock(&command_mutex);
    Tcl_ConditionNotify(ev->done);
    Tcl_MutexUnlock(&command_mutex);
    return 1;
}
#endif

static PyObject *
Tkapp_CreateCommand(PyObject *selfptr, PyObject *args)
{
    TkappObject *self = (TkappObject*)selfptr;
    PythonCmd_ClientData *data;
    char *cmdName;
    PyObject *func;
    int err;

    if (!PyArg_ParseTuple(args, "sO:createcommand", &cmdName, &func))
        return NULL;
    CHECK_STRING_LENGTH(cmdName);
    if (!PyCallable_Check(func)) {
        PyErr_SetString(PyExc_TypeError, "command not callable");
        return NULL;
    }

#ifdef WITH_THREAD
    if (self->threaded && self->thread_id != Tcl_GetCurrentThread() &&
        !WaitForMainloop(self))
        return NULL;
#endif

    data = PyMem_NEW(PythonCmd_ClientData, 1);
    if (!data)
        return PyErr_NoMemory();
    Py_INCREF(self);
    Py_INCREF(func);
    data->self = selfptr;
    data->func = func;
#ifdef WITH_THREAD
    if (self->threaded && self->thread_id != Tcl_GetCurrentThread()) {
        Tcl_Condition cond = NULL;
        CommandEvent *ev = (CommandEvent*)ckalloc(sizeof(CommandEvent));
        ev->ev.proc = (Tcl_EventProc*)Tkapp_CommandProc;
        ev->interp = self->interp;
        ev->create = 1;
        ev->name = cmdName;
        ev->data = (ClientData)data;
        ev->status = &err;
        ev->done = &cond;
        Tkapp_ThreadSend(self, (Tcl_Event*)ev, &cond, &command_mutex);
        Tcl_ConditionFinalize(&cond);
    }
    else
#endif
    {
        ENTER_TCL
        err = Tcl_CreateCommand(
            Tkapp_Interp(self), cmdName, PythonCmd,
            (ClientData)data, PythonCmdDelete) == NULL;
        LEAVE_TCL
    }
    if (err) {
        PyErr_SetString(Tkinter_TclError, "can't create Tcl command");
        PyMem_DEL(data);
        return NULL;
    }

    Py_RETURN_NONE;
}



static PyObject *
Tkapp_DeleteCommand(PyObject *selfptr, PyObject *args)
{
    TkappObject *self = (TkappObject*)selfptr;
    char *cmdName;
    int err;

    if (!PyArg_ParseTuple(args, "s:deletecommand", &cmdName))
        return NULL;
    CHECK_STRING_LENGTH(cmdName);

#ifdef WITH_THREAD
    if (self->threaded && self->thread_id != Tcl_GetCurrentThread()) {
        Tcl_Condition cond = NULL;
        CommandEvent *ev;
        ev = (CommandEvent*)ckalloc(sizeof(CommandEvent));
        ev->ev.proc = (Tcl_EventProc*)Tkapp_CommandProc;
        ev->interp = self->interp;
        ev->create = 0;
        ev->name = cmdName;
        ev->status = &err;
        ev->done = &cond;
        Tkapp_ThreadSend(self, (Tcl_Event*)ev, &cond,
                         &command_mutex);
        Tcl_ConditionFinalize(&cond);
    }
    else
#endif
    {
        ENTER_TCL
        err = Tcl_DeleteCommand(self->interp, cmdName);
        LEAVE_TCL
    }
    if (err == -1) {
        PyErr_SetString(Tkinter_TclError, "can't delete Tcl command");
        return NULL;
    }
    Py_RETURN_NONE;
}



#ifdef HAVE_CREATEFILEHANDLER
/** File Handler **/

typedef struct _fhcdata {
    PyObject *func;
    PyObject *file;
    int id;
    struct _fhcdata *next;
} FileHandler_ClientData;

static FileHandler_ClientData *HeadFHCD;

static FileHandler_ClientData *
NewFHCD(PyObject *func, PyObject *file, int id)
{
    FileHandler_ClientData *p;
    p = PyMem_NEW(FileHandler_ClientData, 1);
    if (p != NULL) {
        Py_XINCREF(func);
        Py_XINCREF(file);
        p->func = func;
        p->file = file;
        p->id = id;
        p->next = HeadFHCD;
        HeadFHCD = p;
    }
    return p;
}

static void
DeleteFHCD(int id)
{
    FileHandler_ClientData *p, **pp;

    pp = &HeadFHCD;
    while ((p = *pp) != NULL) {
        if (p->id == id) {
            *pp = p->next;
            Py_XDECREF(p->func);
            Py_XDECREF(p->file);
            PyMem_DEL(p);
        }
        else
            pp = &p->next;
    }
}

static void
FileHandler(ClientData clientData, int mask)
{
    FileHandler_ClientData *data = (FileHandler_ClientData *)clientData;
    PyObject *func, *file, *arg, *res;

    ENTER_PYTHON
    func = data->func;
    file = data->file;

    arg = Py_BuildValue("(Oi)", file, (long) mask);
    res = PyEval_CallObject(func, arg);
    Py_DECREF(arg);

    if (res == NULL) {
        errorInCmd = 1;
        PyErr_Fetch(&excInCmd, &valInCmd, &trbInCmd);
    }
    Py_XDECREF(res);
    LEAVE_PYTHON
}

static PyObject *
Tkapp_CreateFileHandler(PyObject *self, PyObject *args)
     /* args is (file, mask, func) */
{
    FileHandler_ClientData *data;
    PyObject *file, *func;
    int mask, tfile;

    if (!PyArg_ParseTuple(args, "OiO:createfilehandler",
                          &file, &mask, &func))
        return NULL;

    CHECK_TCL_APPARTMENT;

    tfile = PyObject_AsFileDescriptor(file);
    if (tfile < 0)
        return NULL;
    if (!PyCallable_Check(func)) {
        PyErr_SetString(PyExc_TypeError, "bad argument list");
        return NULL;
    }

    data = NewFHCD(func, file, tfile);
    if (data == NULL)
        return NULL;

    /* Ought to check for null Tcl_File object... */
    ENTER_TCL
    Tcl_CreateFileHandler(tfile, mask, FileHandler, (ClientData) data);
    LEAVE_TCL
    Py_RETURN_NONE;
}

static PyObject *
Tkapp_DeleteFileHandler(PyObject *self, PyObject *args)
{
    PyObject *file;
    int tfile;

    if (!PyArg_ParseTuple(args, "O:deletefilehandler", &file))
        return NULL;

    CHECK_TCL_APPARTMENT;

    tfile = PyObject_AsFileDescriptor(file);
    if (tfile < 0)
        return NULL;

    DeleteFHCD(tfile);

    /* Ought to check for null Tcl_File object... */
    ENTER_TCL
    Tcl_DeleteFileHandler(tfile);
    LEAVE_TCL
    Py_RETURN_NONE;
}
#endif /* HAVE_CREATEFILEHANDLER */


/**** Tktt Object (timer token) ****/

static PyObject *Tktt_Type;

typedef struct {
    PyObject_HEAD
    Tcl_TimerToken token;
    PyObject *func;
} TkttObject;

static PyObject *
Tktt_DeleteTimerHandler(PyObject *self, PyObject *args)
{
    TkttObject *v = (TkttObject *)self;
    PyObject *func = v->func;

    if (!PyArg_ParseTuple(args, ":deletetimerhandler"))
        return NULL;
    if (v->token != NULL) {
        Tcl_DeleteTimerHandler(v->token);
        v->token = NULL;
    }
    if (func != NULL) {
        v->func = NULL;
        Py_DECREF(func);
        Py_DECREF(v); /* See Tktt_New() */
    }
    Py_RETURN_NONE;
}

static PyMethodDef Tktt_methods[] =
{
    {"deletetimerhandler", Tktt_DeleteTimerHandler, METH_VARARGS},
    {NULL, NULL}
};

static TkttObject *
Tktt_New(PyObject *func)
{
    TkttObject *v;

    v = PyObject_New(TkttObject, (PyTypeObject *) Tktt_Type);
    if (v == NULL)
        return NULL;
    Py_INCREF(Tktt_Type);

    Py_INCREF(func);
    v->token = NULL;
    v->func = func;

    /* Extra reference, deleted when called or when handler is deleted */
    Py_INCREF(v);
    return v;
}

static void
Tktt_Dealloc(PyObject *self)
{
    TkttObject *v = (TkttObject *)self;
    PyObject *func = v->func;
    PyObject *tp = (PyObject *) Py_TYPE(self);

    Py_XDECREF(func);

    PyObject_Del(self);
    Py_DECREF(tp);
}

static PyObject *
Tktt_Repr(PyObject *self)
{
    TkttObject *v = (TkttObject *)self;
    return PyUnicode_FromFormat("<tktimertoken at %p%s>",
                                v,
                                v->func == NULL ? ", handler deleted" : "");
}

static PyType_Slot Tktt_Type_slots[] = {
    {Py_tp_dealloc, Tktt_Dealloc},
    {Py_tp_repr, Tktt_Repr},
    {Py_tp_methods, Tktt_methods},
    {0, 0}
};

static PyType_Spec Tktt_Type_spec = {
    "tktimertoken",
    sizeof(TkttObject),
    0,
    Py_TPFLAGS_DEFAULT,
    Tktt_Type_slots,
};


/** Timer Handler **/

static void
TimerHandler(ClientData clientData)
{
    TkttObject *v = (TkttObject *)clientData;
    PyObject *func = v->func;
    PyObject *res;

    if (func == NULL)
        return;

    v->func = NULL;

    ENTER_PYTHON

    res  = PyEval_CallObject(func, NULL);
    Py_DECREF(func);
    Py_DECREF(v); /* See Tktt_New() */

    if (res == NULL) {
        errorInCmd = 1;
        PyErr_Fetch(&excInCmd, &valInCmd, &trbInCmd);
    }
    else
        Py_DECREF(res);

    LEAVE_PYTHON
}

static PyObject *
Tkapp_CreateTimerHandler(PyObject *self, PyObject *args)
{
    int milliseconds;
    PyObject *func;
    TkttObject *v;

    if (!PyArg_ParseTuple(args, "iO:createtimerhandler",
                          &milliseconds, &func))
        return NULL;
    if (!PyCallable_Check(func)) {
        PyErr_SetString(PyExc_TypeError, "bad argument list");
        return NULL;
    }

    CHECK_TCL_APPARTMENT;

    v = Tktt_New(func);
    if (v) {
        v->token = Tcl_CreateTimerHandler(milliseconds, TimerHandler,
                                          (ClientData)v);
    }

    return (PyObject *) v;
}


/** Event Loop **/

static PyObject *
Tkapp_MainLoop(PyObject *selfptr, PyObject *args)
{
    int threshold = 0;
    TkappObject *self = (TkappObject*)selfptr;
#ifdef WITH_THREAD
    PyThreadState *tstate = PyThreadState_Get();
#endif

    if (!PyArg_ParseTuple(args, "|i:mainloop", &threshold))
        return NULL;

    CHECK_TCL_APPARTMENT;
    self->dispatching = 1;

    quitMainLoop = 0;
    while (Tk_GetNumMainWindows() > threshold &&
           !quitMainLoop &&
           !errorInCmd)
    {
        int result;

#ifdef WITH_THREAD
        if (self->threaded) {
            /* Allow other Python threads to run. */
            ENTER_TCL
            result = Tcl_DoOneEvent(0);
            LEAVE_TCL
        }
        else {
            Py_BEGIN_ALLOW_THREADS
            if(tcl_lock)PyThread_acquire_lock(tcl_lock, 1);
            tcl_tstate = tstate;
            result = Tcl_DoOneEvent(TCL_DONT_WAIT);
            tcl_tstate = NULL;
            if(tcl_lock)PyThread_release_lock(tcl_lock);
            if (result == 0)
                Sleep(Tkinter_busywaitinterval);
            Py_END_ALLOW_THREADS
        }
#else
        result = Tcl_DoOneEvent(0);
#endif

        if (PyErr_CheckSignals() != 0) {
            self->dispatching = 0;
            return NULL;
        }
        if (result < 0)
            break;
    }
    self->dispatching = 0;
    quitMainLoop = 0;

    if (errorInCmd) {
        errorInCmd = 0;
        PyErr_Restore(excInCmd, valInCmd, trbInCmd);
        excInCmd = valInCmd = trbInCmd = NULL;
        return NULL;
    }
    Py_RETURN_NONE;
}

static PyObject *
Tkapp_DoOneEvent(PyObject *self, PyObject *args)
{
    int flags = 0;
    int rv;

    if (!PyArg_ParseTuple(args, "|i:dooneevent", &flags))
        return NULL;

    ENTER_TCL
    rv = Tcl_DoOneEvent(flags);
    LEAVE_TCL
    return Py_BuildValue("i", rv);
}

static PyObject *
Tkapp_Quit(PyObject *self, PyObject *args)
{

    if (!PyArg_ParseTuple(args, ":quit"))
        return NULL;

    quitMainLoop = 1;
    Py_RETURN_NONE;
}

static PyObject *
Tkapp_InterpAddr(PyObject *self, PyObject *args)
{

    if (!PyArg_ParseTuple(args, ":interpaddr"))
        return NULL;

    return PyLong_FromVoidPtr(Tkapp_Interp(self));
}

static PyObject *
Tkapp_TkInit(PyObject *self, PyObject *args)
{
    Tcl_Interp *interp = Tkapp_Interp(self);
    const char * _tk_exists = NULL;
    int err;

#ifdef TKINTER_PROTECT_LOADTK
    /* Up to Tk 8.4.13, Tk_Init deadlocks on the second call when the
     * first call failed.
     * To avoid the deadlock, we just refuse the second call through
     * a static variable.
     */
    if (tk_load_failed) {
        PyErr_SetString(Tkinter_TclError, TKINTER_LOADTK_ERRMSG);
        return NULL;
    }
#endif

    /* We want to guard against calling Tk_Init() multiple times */
    CHECK_TCL_APPARTMENT;
    ENTER_TCL
    err = Tcl_Eval(Tkapp_Interp(self), "info exists     tk_version");
    ENTER_OVERLAP
    if (err == TCL_ERROR) {
        /* This sets an exception, but we cannot return right
           away because we need to exit the overlap first. */
        Tkinter_Error(self);
    } else {
        _tk_exists = Tkapp_Result(self);
    }
    LEAVE_OVERLAP_TCL
    if (err == TCL_ERROR) {
        return NULL;
    }
    if (_tk_exists == NULL || strcmp(_tk_exists, "1") != 0)     {
        if (Tk_Init(interp)             == TCL_ERROR) {
            PyErr_SetString(Tkinter_TclError,
                            Tcl_GetStringResult(Tkapp_Interp(self)));
#ifdef TKINTER_PROTECT_LOADTK
            tk_load_failed = 1;
#endif
            return NULL;
        }
    }
    Py_RETURN_NONE;
}

static PyObject *
Tkapp_WantObjects(PyObject *self, PyObject *args)
{

    int wantobjects = -1;
    if (!PyArg_ParseTuple(args, "|i:wantobjects", &wantobjects))
        return NULL;
    if (wantobjects == -1)
        return PyBool_FromLong(((TkappObject*)self)->wantobjects);
    ((TkappObject*)self)->wantobjects = wantobjects;

    Py_RETURN_NONE;
}

static PyObject *
Tkapp_WillDispatch(PyObject *self, PyObject *args)
{

    ((TkappObject*)self)->dispatching = 1;

    Py_RETURN_NONE;
}


/**** Tkapp Method List ****/

static PyMethodDef Tkapp_methods[] =
{
    {"willdispatch",       Tkapp_WillDispatch, METH_NOARGS},
    {"wantobjects",            Tkapp_WantObjects, METH_VARARGS},
    {"call",                   Tkapp_Call, METH_VARARGS},
    {"eval",                   Tkapp_Eval, METH_VARARGS},
    {"evalfile",               Tkapp_EvalFile, METH_VARARGS},
    {"record",                 Tkapp_Record, METH_VARARGS},
    {"adderrorinfo",       Tkapp_AddErrorInfo, METH_VARARGS},
    {"setvar",                 Tkapp_SetVar, METH_VARARGS},
    {"globalsetvar",       Tkapp_GlobalSetVar, METH_VARARGS},
    {"getvar",                 Tkapp_GetVar, METH_VARARGS},
    {"globalgetvar",       Tkapp_GlobalGetVar, METH_VARARGS},
    {"unsetvar",               Tkapp_UnsetVar, METH_VARARGS},
    {"globalunsetvar",     Tkapp_GlobalUnsetVar, METH_VARARGS},
    {"getint",                 Tkapp_GetInt, METH_VARARGS},
    {"getdouble",              Tkapp_GetDouble, METH_VARARGS},
    {"getboolean",             Tkapp_GetBoolean, METH_VARARGS},
    {"exprstring",             Tkapp_ExprString, METH_VARARGS},
    {"exprlong",               Tkapp_ExprLong, METH_VARARGS},
    {"exprdouble",             Tkapp_ExprDouble, METH_VARARGS},
    {"exprboolean",        Tkapp_ExprBoolean, METH_VARARGS},
    {"splitlist",              Tkapp_SplitList, METH_VARARGS},
    {"split",                  Tkapp_Split, METH_VARARGS},
    {"createcommand",      Tkapp_CreateCommand, METH_VARARGS},
    {"deletecommand",      Tkapp_DeleteCommand, METH_VARARGS},
#ifdef HAVE_CREATEFILEHANDLER
    {"createfilehandler",  Tkapp_CreateFileHandler, METH_VARARGS},
    {"deletefilehandler",  Tkapp_DeleteFileHandler, METH_VARARGS},
#endif
    {"createtimerhandler", Tkapp_CreateTimerHandler, METH_VARARGS},
    {"mainloop",               Tkapp_MainLoop, METH_VARARGS},
    {"dooneevent",             Tkapp_DoOneEvent, METH_VARARGS},
    {"quit",                   Tkapp_Quit, METH_VARARGS},
    {"interpaddr",         Tkapp_InterpAddr, METH_VARARGS},
    {"loadtk",                 Tkapp_TkInit, METH_NOARGS},
    {NULL,                     NULL}
};



/**** Tkapp Type Methods ****/

static void
Tkapp_Dealloc(PyObject *self)
{
    PyObject *tp = (PyObject *) Py_TYPE(self);
    /*CHECK_TCL_APPARTMENT;*/
    ENTER_TCL
    Tcl_DeleteInterp(Tkapp_Interp(self));
    LEAVE_TCL
    PyObject_Del(self);
    Py_DECREF(tp);
    DisableEventHook();
}

static PyType_Slot Tkapp_Type_slots[] = {
    {Py_tp_dealloc, Tkapp_Dealloc},
    {Py_tp_methods, Tkapp_methods},
    {0, 0}
};


static PyType_Spec Tkapp_Type_spec = {
    "tkapp",
    sizeof(TkappObject),
    0,
    Py_TPFLAGS_DEFAULT,
    Tkapp_Type_slots,
};



/**** Tkinter Module ****/

typedef struct {
    PyObject* tuple;
    int size; /* current size */
    int maxsize; /* allocated size */
} FlattenContext;

static int
_bump(FlattenContext* context, int size)
{
    /* expand tuple to hold (at least) size new items.
       return true if successful, false if an exception was raised */

    int maxsize = context->maxsize * 2;

    if (maxsize < context->size + size)
        maxsize = context->size + size;

    context->maxsize = maxsize;

    return _PyTuple_Resize(&context->tuple, maxsize) >= 0;
}

static int
_flatten1(FlattenContext* context, PyObject* item, int depth)
{
    /* add tuple or list to argument tuple (recursively) */

    int i, size;

    if (depth > 1000) {
        PyErr_SetString(PyExc_ValueError,
                        "nesting too deep in _flatten");
        return 0;
    } else if (PyList_Check(item)) {
        size = PyList_GET_SIZE(item);
        /* preallocate (assume no nesting) */
        if (context->size + size > context->maxsize &&
            !_bump(context, size))
            return 0;
        /* copy items to output tuple */
        for (i = 0; i < size; i++) {
            PyObject *o = PyList_GET_ITEM(item, i);
            if (PyList_Check(o) || PyTuple_Check(o)) {
                if (!_flatten1(context, o, depth + 1))
                    return 0;
            } else if (o != Py_None) {
                if (context->size + 1 > context->maxsize &&
                    !_bump(context, 1))
                    return 0;
                Py_INCREF(o);
                PyTuple_SET_ITEM(context->tuple,
                                 context->size++, o);
            }
        }
    } else if (PyTuple_Check(item)) {
        /* same, for tuples */
        size = PyTuple_GET_SIZE(item);
        if (context->size + size > context->maxsize &&
            !_bump(context, size))
            return 0;
        for (i = 0; i < size; i++) {
            PyObject *o = PyTuple_GET_ITEM(item, i);
            if (PyList_Check(o) || PyTuple_Check(o)) {
                if (!_flatten1(context, o, depth + 1))
                    return 0;
            } else if (o != Py_None) {
                if (context->size + 1 > context->maxsize &&
                    !_bump(context, 1))
                    return 0;
                Py_INCREF(o);
                PyTuple_SET_ITEM(context->tuple,
                                 context->size++, o);
            }
        }
    } else {
        PyErr_SetString(PyExc_TypeError, "argument must be sequence");
        return 0;
    }
    return 1;
}

static PyObject *
Tkinter_Flatten(PyObject* self, PyObject* args)
{
    FlattenContext context;
    PyObject* item;

    if (!PyArg_ParseTuple(args, "O:_flatten", &item))
        return NULL;

    context.maxsize = PySequence_Size(item);
    if (context.maxsize < 0)
        return NULL;
    if (context.maxsize == 0)
        return PyTuple_New(0);

    context.tuple = PyTuple_New(context.maxsize);
    if (!context.tuple)
        return NULL;

    context.size = 0;

    if (!_flatten1(&context, item,0))
        return NULL;

    if (_PyTuple_Resize(&context.tuple, context.size))
        return NULL;

    return context.tuple;
}

static PyObject *
Tkinter_Create(PyObject *self, PyObject *args)
{
    char *screenName = NULL;
    char *baseName = NULL; /* XXX this is not used anymore;
                              try getting rid of it. */
    char *className = NULL;
    int interactive = 0;
    int wantobjects = 0;
    int wantTk = 1;     /* If false, then Tk_Init() doesn't get called */
    int sync = 0; /* pass -sync to wish */
    char *use = NULL; /* pass -use to wish */

    className = "Tk";

    if (!PyArg_ParseTuple(args, "|zssiiiiz:create",
                          &screenName, &baseName, &className,
                          &interactive, &wantobjects, &wantTk,
                          &sync, &use))
        return NULL;
    CHECK_STRING_LENGTH(screenName);
    CHECK_STRING_LENGTH(baseName);
    CHECK_STRING_LENGTH(className);
    CHECK_STRING_LENGTH(use);

    return (PyObject *) Tkapp_New(screenName, className,
                                  interactive, wantobjects, wantTk,
                                  sync, use);
}

static PyObject *
Tkinter_setbusywaitinterval(PyObject *self, PyObject *args)
{
    int new_val;
    if (!PyArg_ParseTuple(args, "i:setbusywaitinterval", &new_val))
        return NULL;
    if (new_val < 0) {
        PyErr_SetString(PyExc_ValueError,
                        "busywaitinterval must be >= 0");
        return NULL;
    }
    Tkinter_busywaitinterval = new_val;
    Py_RETURN_NONE;
}

static char setbusywaitinterval_doc[] =
"setbusywaitinterval(n) -> None\n\
\n\
Set the busy-wait interval in milliseconds between successive\n\
calls to Tcl_DoOneEvent in a threaded Python interpreter.\n\
It should be set to a divisor of the maximum time between\n\
frames in an animation.";

static PyObject *
Tkinter_getbusywaitinterval(PyObject *self, PyObject *args)
{
    return PyLong_FromLong(Tkinter_busywaitinterval);
}

static char getbusywaitinterval_doc[] =
"getbusywaitinterval() -> int\n\
\n\
Return the current busy-wait interval between successive\n\
calls to Tcl_DoOneEvent in a threaded Python interpreter.";

static PyMethodDef moduleMethods[] =
{
    {"_flatten",           Tkinter_Flatten, METH_VARARGS},
    {"create",             Tkinter_Create, METH_VARARGS},
    {"setbusywaitinterval",Tkinter_setbusywaitinterval, METH_VARARGS,
                           setbusywaitinterval_doc},
    {"getbusywaitinterval",(PyCFunction)Tkinter_getbusywaitinterval,
                           METH_NOARGS, getbusywaitinterval_doc},
    {NULL,                 NULL}
};

#ifdef WAIT_FOR_STDIN

static int stdin_ready = 0;

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

#ifdef WITH_THREAD
static PyThreadState *event_tstate = NULL;
#endif

static int
EventHook(void)
{
#ifndef MS_WINDOWS
    int tfile;
#endif
#ifdef WITH_THREAD
    PyEval_RestoreThread(event_tstate);
#endif
    stdin_ready = 0;
    errorInCmd = 0;
#ifndef MS_WINDOWS
    tfile = fileno(stdin);
    Tcl_CreateFileHandler(tfile, TCL_READABLE, MyFileProc, NULL);
#endif
    while (!errorInCmd && !stdin_ready) {
        int result;
#ifdef MS_WINDOWS
        if (_kbhit()) {
            stdin_ready = 1;
            break;
        }
#endif
#if defined(WITH_THREAD) || defined(MS_WINDOWS)
        Py_BEGIN_ALLOW_THREADS
        if(tcl_lock)PyThread_acquire_lock(tcl_lock, 1);
        tcl_tstate = event_tstate;

        result = Tcl_DoOneEvent(TCL_DONT_WAIT);

        tcl_tstate = NULL;
        if(tcl_lock)PyThread_release_lock(tcl_lock);
        if (result == 0)
            Sleep(Tkinter_busywaitinterval);
        Py_END_ALLOW_THREADS
#else
        result = Tcl_DoOneEvent(0);
#endif

        if (result < 0)
            break;
    }
#ifndef MS_WINDOWS
    Tcl_DeleteFileHandler(tfile);
#endif
    if (errorInCmd) {
        errorInCmd = 0;
        PyErr_Restore(excInCmd, valInCmd, trbInCmd);
        excInCmd = valInCmd = trbInCmd = NULL;
        PyErr_Print();
    }
#ifdef WITH_THREAD
    PyEval_SaveThread();
#endif
    return 0;
}

#endif

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

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


static struct PyModuleDef _tkintermodule = {
    PyModuleDef_HEAD_INIT,
    "_tkinter",
    NULL,
    -1,
    moduleMethods,
    NULL,
    NULL,
    NULL,
    NULL
};

PyMODINIT_FUNC
PyInit__tkinter(void)
{
  PyObject *m, *uexe, *cexe, *o;

#ifdef WITH_THREAD
    tcl_lock = PyThread_allocate_lock();
    if (tcl_lock == NULL)
        return NULL;
#endif

    m = PyModule_Create(&_tkintermodule);
    if (m == NULL)
        return NULL;

    o = PyErr_NewException("_tkinter.TclError", NULL, NULL);
    if (o == NULL) {
        Py_DECREF(m);
        return NULL;
    }
    Py_INCREF(o);
    if (PyModule_AddObject(m, "TclError", o)) {
        Py_DECREF(o);
        Py_DECREF(m);
        return NULL;
    }
    Tkinter_TclError = o;

    if (PyModule_AddIntConstant(m, "READABLE", TCL_READABLE)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddIntConstant(m, "WRITABLE", TCL_WRITABLE)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddIntConstant(m, "EXCEPTION", TCL_EXCEPTION)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddIntConstant(m, "WINDOW_EVENTS", TCL_WINDOW_EVENTS)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddIntConstant(m, "FILE_EVENTS", TCL_FILE_EVENTS)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddIntConstant(m, "TIMER_EVENTS", TCL_TIMER_EVENTS)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddIntConstant(m, "IDLE_EVENTS", TCL_IDLE_EVENTS)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddIntConstant(m, "ALL_EVENTS", TCL_ALL_EVENTS)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddIntConstant(m, "DONT_WAIT", TCL_DONT_WAIT)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddStringConstant(m, "TK_VERSION", TK_VERSION)) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddStringConstant(m, "TCL_VERSION", TCL_VERSION)) {
        Py_DECREF(m);
        return NULL;
    }

    o = PyType_FromSpec(&Tkapp_Type_spec);
    if (o == NULL) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddObject(m, "TkappType", o)) {
        Py_DECREF(o);
        Py_DECREF(m);
        return NULL;
    }
    Tkapp_Type = o;

    o = PyType_FromSpec(&Tktt_Type_spec);
    if (o == NULL) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddObject(m, "TkttType", o)) {
        Py_DECREF(o);
        Py_DECREF(m);
        return NULL;
    }
    Tktt_Type = o;

    o = PyType_FromSpec(&PyTclObject_Type_spec);
    if (o == NULL) {
        Py_DECREF(m);
        return NULL;
    }
    if (PyModule_AddObject(m, "Tcl_Obj", o)) {
        Py_DECREF(o);
        Py_DECREF(m);
        return NULL;
    }
    PyTclObject_Type = o;

#ifdef TK_AQUA
    /* Tk_MacOSXSetupTkNotifier must be called before Tcl's subsystems
     * start waking up.  Note that Tcl_FindExecutable will do this, this
     * code must be above it! The original warning from
     * tkMacOSXAppInit.c is copied below.
     *
     * NB - You have to swap in the Tk Notifier BEFORE you start up the
     * Tcl interpreter for now.  It probably should work to do this
     * in the other order, but for now it doesn't seem to.
     *
     */
    Tk_MacOSXSetupTkNotifier();
#endif


    /* This helps the dynamic loader; in Unicode aware Tcl versions
       it also helps Tcl find its encodings. */
    uexe = PyUnicode_FromWideChar(Py_GetProgramName(), -1);
    if (uexe) {
        cexe = PyUnicode_EncodeFSDefault(uexe);
        if (cexe)
            Tcl_FindExecutable(PyBytes_AsString(cexe));
        Py_XDECREF(cexe);
        Py_DECREF(uexe);
    }

    if (PyErr_Occurred()) {
        Py_DECREF(m);
        return NULL;
    }

#if 0
    /* This was not a good idea; through <Destroy> bindings,
       Tcl_Finalize() may invoke Python code but at that point the
       interpreter and thread state have already been destroyed! */
    Py_AtExit(Tcl_Finalize);
#endif
    return m;
}