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tkUnixSend.c

/* 
 * tkUnixSend.c --
 *
 *    This file provides procedures that implement the "send"
 *    command, allowing commands to be passed from interpreter
 *    to interpreter.
 *
 * Copyright (c) 1989-1994 The Regents of the University of California.
 * Copyright (c) 1994-1996 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tkUnixSend.c,v 1.2 1998/09/14 18:23:58 stanton Exp $
 */

#include "tkPort.h"
#include "tkInt.h"
#include "tkUnixInt.h"

/* 
 * The following structure is used to keep track of the interpreters
 * registered by this process.
 */

typedef struct RegisteredInterp {
    char *name;               /* Interpreter's name (malloc-ed). */
    Tcl_Interp *interp;       /* Interpreter associated with name.  NULL
                         * means that the application was unregistered
                         * or deleted while a send was in progress
                         * to it. */
    TkDisplay *dispPtr;       /* Display for the application.  Needed
                         * because we may need to unregister the
                         * interpreter after its main window has
                         * been deleted. */
    struct RegisteredInterp *nextPtr;
                        /* Next in list of names associated
                         * with interps in this process.
                         * NULL means end of list. */
} RegisteredInterp;

static RegisteredInterp *registry = NULL;
                        /* List of all interpreters
                         * registered by this process. */

/*
 * A registry of all interpreters for a display is kept in a
 * property "InterpRegistry" on the root window of the display.
 * It is organized as a series of zero or more concatenated strings
 * (in no particular order), each of the form
 *    window space name '\0'
 * where "window" is the hex id of the comm. window to use to talk
 * to an interpreter named "name".
 *
 * When the registry is being manipulated by an application (e.g. to
 * add or remove an entry), it is loaded into memory using a structure
 * of the following type:
 */

typedef struct NameRegistry {
    TkDisplay *dispPtr;       /* Display from which the registry was
                         * read. */
    int locked;               /* Non-zero means that the display was
                         * locked when the property was read in. */
    int modified;       /* Non-zero means that the property has
                         * been modified, so it needs to be written
                         * out when the NameRegistry is closed. */
    unsigned long propLength; /* Length of the property, in bytes. */
    char *property;           /* The contents of the property, or NULL
                         * if none.  See format description above;
                         * this is *not* terminated by the first
                         * null character.  Dynamically allocated. */
    int allocedByX;           /* Non-zero means must free property with
                         * XFree;  zero means use ckfree. */
} NameRegistry;

/*
 * When a result is being awaited from a sent command, one of
 * the following structures is present on a list of all outstanding
 * sent commands.  The information in the structure is used to
 * process the result when it arrives.  You're probably wondering
 * how there could ever be multiple outstanding sent commands.
 * This could happen if interpreters invoke each other recursively.
 * It's unlikely, but possible.
 */

typedef struct PendingCommand {
    int serial;               /* Serial number expected in
                         * result. */
    TkDisplay *dispPtr;       /* Display being used for communication. */
    char *target;       /* Name of interpreter command is
                         * being sent to. */
    Window commWindow;        /* Target's communication window. */
    Tcl_Interp *interp;       /* Interpreter from which the send
                         * was invoked. */
    int code;                 /* Tcl return code for command
                         * will be stored here. */
    char *result;       /* String result for command (malloc'ed),
                         * or NULL. */
    char *errorInfo;          /* Information for "errorInfo" variable,
                         * or NULL (malloc'ed). */
    char *errorCode;          /* Information for "errorCode" variable,
                         * or NULL (malloc'ed). */
    int gotResponse;          /* 1 means a response has been received,
                         * 0 means the command is still outstanding. */
    struct PendingCommand *nextPtr;
                        /* Next in list of all outstanding
                         * commands.  NULL means end of
                         * list. */
} PendingCommand;

static PendingCommand *pendingCommands = NULL;
                        /* List of all commands currently
                         * being waited for. */

/*
 * The information below is used for communication between processes
 * during "send" commands.  Each process keeps a private window, never
 * even mapped, with one property, "Comm".  When a command is sent to
 * an interpreter, the command is appended to the comm property of the
 * communication window associated with the interp's process.  Similarly,
 * when a result is returned from a sent command, it is also appended
 * to the comm property.
 *
 * Each command and each result takes the form of ASCII text.  For a
 * command, the text consists of a zero character followed by several
 * null-terminated ASCII strings.  The first string consists of the
 * single letter "c".  Subsequent strings have the form "option value"
 * where the following options are supported:
 *
 * -r commWindow serial
 *
 *    This option means that a response should be sent to the window
 *    whose X identifier is "commWindow" (in hex), and the response should
 *    be identified with the serial number given by "serial" (in decimal).
 *    If this option isn't specified then the send is asynchronous and
 *    no response is sent.
 *
 * -n name
 *    "Name" gives the name of the application for which the command is
 *    intended.  This option must be present.
 *
 * -s script
 *
 *    "Script" is the script to be executed.  This option must be present.
 *
 * The options may appear in any order.  The -n and -s options must be
 * present, but -r may be omitted for asynchronous RPCs.  For compatibility
 * with future releases that may add new features, there may be additional
 * options present;  as long as they start with a "-" character, they will
 * be ignored.
 *
 * A result also consists of a zero character followed by several null-
 * terminated ASCII strings.  The first string consists of the single
 * letter "r".  Subsequent strings have the form "option value" where
 * the following options are supported:
 *
 * -s serial
 *
 *    Identifies the command for which this is the result.  It is the
 *    same as the "serial" field from the -s option in the command.  This
 *    option must be present.
 *
 * -c code
 *
 *    "Code" is the completion code for the script, in decimal.  If the
 *    code is omitted it defaults to TCL_OK.
 *
 * -r result
 *
 *    "Result" is the result string for the script, which may be either
 *    a result or an error message.  If this field is omitted then it
 *    defaults to an empty string.
 *
 * -i errorInfo
 *
 *    "ErrorInfo" gives a string with which to initialize the errorInfo
 *    variable.  This option may be omitted;  it is ignored unless the
 *    completion code is TCL_ERROR.
 *
 * -e errorCode
 *
 *    "ErrorCode" gives a string with with to initialize the errorCode
 *    variable.  This option may be omitted;  it is ignored  unless the
 *    completion code is TCL_ERROR.
 *
 * Options may appear in any order, and only the -s option must be
 * present.  As with commands, there may be additional options besides
 * these;  unknown options are ignored.
 */

/*
 * The following variable is the serial number that was used in the
 * last "send" command.  It is exported only for testing purposes.
 */

int tkSendSerial = 0;

/*
 * Maximum size property that can be read at one time by
 * this module:
 */

#define MAX_PROP_WORDS 100000

/*
 * The following variable can be set while debugging to do things like
 * skip locking the server.
 */

static int sendDebug = 0;

/*
 * Forward declarations for procedures defined later in this file:
 */

static int        AppendErrorProc _ANSI_ARGS_((ClientData clientData,
                        XErrorEvent *errorPtr));
static void       AppendPropCarefully _ANSI_ARGS_((Display *display,
                      Window window, Atom property, char *value,
                      int length, PendingCommand *pendingPtr));
static void       DeleteProc _ANSI_ARGS_((ClientData clientData));
static void       RegAddName _ANSI_ARGS_((NameRegistry *regPtr,
                      char *name, Window commWindow));
static void       RegClose _ANSI_ARGS_((NameRegistry *regPtr));
static void       RegDeleteName _ANSI_ARGS_((NameRegistry *regPtr,
                      char *name));
static Window           RegFindName _ANSI_ARGS_((NameRegistry *regPtr,
                      char *name));
static NameRegistry *   RegOpen _ANSI_ARGS_((Tcl_Interp *interp,
                      TkDisplay *dispPtr, int lock));
static void       SendEventProc _ANSI_ARGS_((ClientData clientData,
                      XEvent *eventPtr));
static int        SendInit _ANSI_ARGS_((Tcl_Interp *interp,
                      TkDisplay *dispPtr));
static Tk_RestrictAction SendRestrictProc _ANSI_ARGS_((ClientData clientData,
                      XEvent *eventPtr));
static int        ServerSecure _ANSI_ARGS_((TkDisplay *dispPtr));
static void       UpdateCommWindow _ANSI_ARGS_((TkDisplay *dispPtr));
static int        ValidateName _ANSI_ARGS_((TkDisplay *dispPtr,
                      char *name, Window commWindow, int oldOK));

/*
 *----------------------------------------------------------------------
 *
 * RegOpen --
 *
 *    This procedure loads the name registry for a display into
 *    memory so that it can be manipulated.
 *
 * Results:
 *    The return value is a pointer to the loaded registry.
 *
 * Side effects:
 *    If "lock" is set then the server will be locked.  It is the
 *    caller's responsibility to call RegClose when finished with
 *    the registry, so that we can write back the registry if
 *    neeeded, unlock the server if needed, and free memory.
 *
 *----------------------------------------------------------------------
 */

static NameRegistry *
RegOpen(interp, dispPtr, lock)
    Tcl_Interp *interp;       /* Interpreter to use for error reporting
                         * (errors cause a panic so in fact no
                         * error is ever returned, but the interpreter
                         * is needed anyway). */
    TkDisplay *dispPtr;       /* Display whose name registry is to be
                         * opened. */
    int lock;                 /* Non-zero means lock the window server
                         * when opening the registry, so no-one
                         * else can use the registry until we
                         * close it. */
{
    NameRegistry *regPtr;
    int result, actualFormat;
    unsigned long bytesAfter;
    Atom actualType;

    if (dispPtr->commTkwin == NULL) {
      SendInit(interp, dispPtr);
    }

    regPtr = (NameRegistry *) ckalloc(sizeof(NameRegistry));
    regPtr->dispPtr = dispPtr;
    regPtr->locked = 0;
    regPtr->modified = 0;
    regPtr->allocedByX = 1;

    if (lock && !sendDebug) {
      XGrabServer(dispPtr->display);
      regPtr->locked = 1;
    }

    /*
     * Read the registry property.
     */

    result = XGetWindowProperty(dispPtr->display,
          RootWindow(dispPtr->display, 0),
          dispPtr->registryProperty, 0, MAX_PROP_WORDS,
          False, XA_STRING, &actualType, &actualFormat,
          &regPtr->propLength, &bytesAfter,
          (unsigned char **) &regPtr->property);

    if (actualType == None) {
      regPtr->propLength = 0;
      regPtr->property = NULL;
    } else if ((result != Success) || (actualFormat != 8)
          || (actualType != XA_STRING)) {
      /*
       * The property is improperly formed;  delete it.
       */

      if (regPtr->property != NULL) {
          XFree(regPtr->property);
          regPtr->propLength = 0;
          regPtr->property = NULL;
      }
      XDeleteProperty(dispPtr->display,
            RootWindow(dispPtr->display, 0),
            dispPtr->registryProperty);
    }

    /*
     * Xlib placed an extra null byte after the end of the property, just
     * to make sure that it is always NULL-terminated.  Be sure to include
     * this byte in our count if it's needed to ensure null termination
     * (note: as of 8/95 I'm no longer sure why this code is needed;  seems
     * like it shouldn't be).
     */

    if ((regPtr->propLength > 0)
          && (regPtr->property[regPtr->propLength-1] != 0)) {
      regPtr->propLength++;
    }
    return regPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * RegFindName --
 *
 *    Given an open name registry, this procedure finds an entry
 *    with a given name, if there is one, and returns information
 *    about that entry.
 *
 * Results:
 *    The return value is the X identifier for the comm window for
 *    the application named "name", or None if there is no such
 *    entry in the registry.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

static Window
RegFindName(regPtr, name)
    NameRegistry *regPtr;     /* Pointer to a registry opened with a
                         * previous call to RegOpen. */
    char *name;               /* Name of an application. */
{
    char *p, *entry;
    unsigned int id;

    for (p = regPtr->property; (p-regPtr->property) < (int) regPtr->propLength; ) {
      entry = p;
      while ((*p != 0) && (!isspace(UCHAR(*p)))) {
          p++;
      }
      if ((*p != 0) && (strcmp(name, p+1) == 0)) {
          if (sscanf(entry, "%x", &id) == 1) {
            /*
             * Must cast from an unsigned int to a Window in case we
             * are on a 64-bit architecture.
             */

            return (Window) id;
          }
      }
      while (*p != 0) {
          p++;
      }
      p++;
    }
    return None;
}

/*
 *----------------------------------------------------------------------
 *
 * RegDeleteName --
 *
 *    This procedure deletes the entry for a given name from
 *    an open registry.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    If there used to be an entry named "name" in the registry,
 *    then it is deleted and the registry is marked as modified
 *    so it will be written back when closed.
 *
 *----------------------------------------------------------------------
 */

static void
RegDeleteName(regPtr, name)
    NameRegistry *regPtr;     /* Pointer to a registry opened with a
                         * previous call to RegOpen. */
    char *name;               /* Name of an application. */
{
    char *p, *entry, *entryName;
    int count;

    for (p = regPtr->property; (p-regPtr->property) < (int) regPtr->propLength; ) {
      entry = p;
      while ((*p != 0) && (!isspace(UCHAR(*p)))) {
          p++;
      }
      if (*p != 0) {
          p++;
      }
      entryName = p;
      while (*p != 0) {
          p++;
      }
      p++;
      if ((strcmp(name, entryName) == 0)) {
          /*
           * Found the matching entry.  Copy everything after it
           * down on top of it.
           */

          count = regPtr->propLength - (p - regPtr->property);
          if (count > 0)  {
            char *src, *dst;

            for (src = p, dst = entry; count > 0; src++, dst++, count--) {
                *dst = *src;
            }
          }
          regPtr->propLength -=  p - entry;
          regPtr->modified = 1;
          return;
      }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * RegAddName --
 *
 *    Add a new entry to an open registry.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    The open registry is expanded;  it is marked as modified so that
 *    it will be written back when closed.
 *
 *----------------------------------------------------------------------
 */

static void
RegAddName(regPtr, name, commWindow)
    NameRegistry *regPtr;     /* Pointer to a registry opened with a
                         * previous call to RegOpen. */
    char *name;               /* Name of an application.  The caller
                         * must ensure that this name isn't
                         * already registered. */
    Window commWindow;        /* X identifier for comm. window of
                         * application.  */
{
    char id[30];
    char *newProp;
    int idLength, newBytes;

    sprintf(id, "%x ", (unsigned int) commWindow);
    idLength = strlen(id);
    newBytes = idLength + strlen(name) + 1;
    newProp = (char *) ckalloc((unsigned) (regPtr->propLength + newBytes));
    strcpy(newProp, id);
    strcpy(newProp+idLength, name);
    if (regPtr->property != NULL) {
      memcpy((VOID *) (newProp + newBytes), (VOID *) regPtr->property,
            regPtr->propLength);
      if (regPtr->allocedByX) {
          XFree(regPtr->property);
      } else {
          ckfree(regPtr->property);
      }
    }
    regPtr->modified = 1;
    regPtr->propLength += newBytes;
    regPtr->property = newProp;
    regPtr->allocedByX = 0;
}

/*
 *----------------------------------------------------------------------
 *
 * RegClose --
 *
 *    This procedure is called to end a series of operations on
 *    a name registry.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    The registry is written back if it has been modified, and the
 *    X server is unlocked if it was locked.  Memory for the
 *    registry is freed, so the caller should never use regPtr
 *    again.
 *
 *----------------------------------------------------------------------
 */

static void
RegClose(regPtr)
    NameRegistry *regPtr;     /* Pointer to a registry opened with a
                         * previous call to RegOpen. */
{
    if (regPtr->modified) {
      if (!regPtr->locked && !sendDebug) {
          panic("The name registry was modified without being locked!");
      }
      XChangeProperty(regPtr->dispPtr->display,
            RootWindow(regPtr->dispPtr->display, 0),
            regPtr->dispPtr->registryProperty, XA_STRING, 8,
            PropModeReplace, (unsigned char *) regPtr->property,
            (int) regPtr->propLength);
    }

    if (regPtr->locked) {
      XUngrabServer(regPtr->dispPtr->display);
    }

    /*
     * After ungrabbing the server, it's important to flush the output
     * immediately so that the server sees the ungrab command.  Otherwise
     * we might do something else that needs to communicate with the
     * server (such as invoking a subprocess that needs to do I/O to
     * the screen); if the ungrab command is still sitting in our
     * output buffer, we could deadlock.
     */

    XFlush(regPtr->dispPtr->display);

    if (regPtr->property != NULL) {
      if (regPtr->allocedByX) {
          XFree(regPtr->property);
      } else {
          ckfree(regPtr->property);
      }
    }
    ckfree((char *) regPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * ValidateName --
 *
 *    This procedure checks to see if an entry in the registry
 *    is still valid.
 *
 * Results:
 *    The return value is 1 if the given commWindow exists and its
 *    name is "name".  Otherwise 0 is returned.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

static int
ValidateName(dispPtr, name, commWindow, oldOK)
    TkDisplay *dispPtr;       /* Display for which to perform the
                         * validation. */
    char *name;               /* The name of an application. */
    Window commWindow;        /* X identifier for the application's
                         * comm. window. */
    int oldOK;                /* Non-zero means that we should consider
                         * an application to be valid even if it
                         * looks like an old-style (pre-4.0) one;
                         * 0 means consider these invalid. */
{
    int result, actualFormat, argc, i;
    unsigned long length, bytesAfter;
    Atom actualType;
    char *property;
    Tk_ErrorHandler handler;
    char **argv;

    property = NULL;

    /*
     * Ignore X errors when reading the property (e.g., the window
     * might not exist).  If an error occurs, result will be some
     * value other than Success.
     */

    handler = Tk_CreateErrorHandler(dispPtr->display, -1, -1, -1,
          (Tk_ErrorProc *) NULL, (ClientData) NULL);
    result = XGetWindowProperty(dispPtr->display, commWindow,
          dispPtr->appNameProperty, 0, MAX_PROP_WORDS,
          False, XA_STRING, &actualType, &actualFormat,
          &length, &bytesAfter, (unsigned char **) &property);

    if ((result == Success) && (actualType == None)) {
      XWindowAttributes atts;

      /*
       * The comm. window exists but the property we're looking for
       * doesn't exist.  This probably means that the application
       * comes from an older version of Tk (< 4.0) that didn't set the
       * property;  if this is the case, then assume for compatibility's
       * sake that everything's OK.  However, it's also possible that
       * some random application has re-used the window id for something
       * totally unrelated.  Check a few characteristics of the window,
       * such as its dimensions and mapped state, to be sure that it
       * still "smells" like a commWindow.
       */

      if (!oldOK
            || !XGetWindowAttributes(dispPtr->display, commWindow, &atts)
            || (atts.width != 1) || (atts.height != 1)
            || (atts.map_state != IsUnmapped)) {
          result = 0;
      } else {
          result = 1;
      }
    } else if ((result == Success) && (actualFormat == 8)
         && (actualType == XA_STRING)) {
      result = 0;
      if (Tcl_SplitList((Tcl_Interp *) NULL, property, &argc, &argv)
            == TCL_OK) {
          for (i = 0; i < argc; i++) {
            if (strcmp(argv[i], name) == 0) {
                result = 1;
                break;
            }
          }
          ckfree((char *) argv);
      }
    } else {
       result = 0;
    }
    Tk_DeleteErrorHandler(handler);
    if (property != NULL) {
      XFree(property);
    }
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * ServerSecure --
 *
 *    Check whether a server is secure enough for us to trust
 *    Tcl scripts arriving via that server.
 *
 * Results:
 *    The return value is 1 if the server is secure, which means
 *    that host-style authentication is turned on but there are
 *    no hosts in the enabled list.  This means that some other
 *    form of authorization (presumably more secure, such as xauth)
 *    is in use.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

static int
ServerSecure(dispPtr)
    TkDisplay *dispPtr;       /* Display to check. */
{
#ifdef TK_NO_SECURITY
    return 1;
#else
    XHostAddress *addrPtr;
    int numHosts, secure;
    Bool enabled;

    secure = 0;
    addrPtr = XListHosts(dispPtr->display, &numHosts, &enabled);
    if (enabled && (numHosts == 0)) {
      secure = 1;
    }
    if (addrPtr != NULL) {
      XFree((char *) addrPtr);
    }
    return secure;
#endif /* TK_NO_SECURITY */
}

/*
 *--------------------------------------------------------------
 *
 * Tk_SetAppName --
 *
 *    This procedure is called to associate an ASCII name with a Tk
 *    application.  If the application has already been named, the
 *    name replaces the old one.
 *
 * Results:
 *    The return value is the name actually given to the application.
 *    This will normally be the same as name, but if name was already
 *    in use for an application then a name of the form "name #2" will
 *    be chosen,  with a high enough number to make the name unique.
 *
 * Side effects:
 *    Registration info is saved, thereby allowing the "send" command
 *    to be used later to invoke commands in the application.  In
 *    addition, the "send" command is created in the application's
 *    interpreter.  The registration will be removed automatically
 *    if the interpreter is deleted or the "send" command is removed.
 *
 *--------------------------------------------------------------
 */

char *
Tk_SetAppName(tkwin, name)
    Tk_Window tkwin;          /* Token for any window in the application
                         * to be named:  it is just used to identify
                         * the application and the display.  */
    char *name;               /* The name that will be used to
                         * refer to the interpreter in later
                         * "send" commands.  Must be globally
                         * unique. */
{
    RegisteredInterp *riPtr, *riPtr2;
    Window w;
    TkWindow *winPtr = (TkWindow *) tkwin;
    TkDisplay *dispPtr;
    NameRegistry *regPtr;
    Tcl_Interp *interp;
    char *actualName;
    Tcl_DString dString;
    int offset, i;

#ifdef __WIN32__
    return name;
#endif /* __WIN32__ */
    
    dispPtr = winPtr->dispPtr;
    interp = winPtr->mainPtr->interp;
    if (dispPtr->commTkwin == NULL) {
      SendInit(interp, winPtr->dispPtr);
    }

    /*
     * See if the application is already registered;  if so, remove its
     * current name from the registry.
     */

    regPtr = RegOpen(interp, winPtr->dispPtr, 1);
    for (riPtr = registry; ; riPtr = riPtr->nextPtr) {
      if (riPtr == NULL) {

          /*
           * This interpreter isn't currently registered;  create
           * the data structure that will be used to register it locally,
           * plus add the "send" command to the interpreter.
           */

          riPtr = (RegisteredInterp *) ckalloc(sizeof(RegisteredInterp));
          riPtr->interp = interp;
          riPtr->dispPtr = winPtr->dispPtr;
          riPtr->nextPtr = registry;
          registry = riPtr;
          Tcl_CreateCommand(interp, "send", Tk_SendCmd, (ClientData) riPtr,
                DeleteProc);
            if (Tcl_IsSafe(interp)) {
                Tcl_HideCommand(interp, "send", "send");
            }
          break;
      }
      if (riPtr->interp == interp) {
          /*
           * The interpreter is currently registered;  remove it from
           * the name registry.
           */

          RegDeleteName(regPtr, riPtr->name);
          ckfree(riPtr->name);
          break;
      }
    }

    /*
     * Pick a name to use for the application.  Use "name" if it's not
     * already in use.  Otherwise add a suffix such as " #2", trying
     * larger and larger numbers until we eventually find one that is
     * unique.
     */

    actualName = name;
    offset = 0;                     /* Needed only to avoid "used before
                               * set" compiler warnings. */
    for (i = 1; ; i++) {
      if (i > 1) {
          if (i == 2) {
            Tcl_DStringInit(&dString);
            Tcl_DStringAppend(&dString, name, -1);
            Tcl_DStringAppend(&dString, " #", 2);
            offset = Tcl_DStringLength(&dString);
            Tcl_DStringSetLength(&dString, offset+10);
            actualName = Tcl_DStringValue(&dString);
          }
          sprintf(actualName + offset, "%d", i);
      }
      w = RegFindName(regPtr, actualName);
      if (w == None) {
          break;
      }
    
      /*
       * The name appears to be in use already, but double-check to
       * be sure (perhaps the application died without removing its
       * name from the registry?).
       */

      if (w == Tk_WindowId(dispPtr->commTkwin)) {
          for (riPtr2 = registry; riPtr2 != NULL; riPtr2 = riPtr2->nextPtr) {
            if ((riPtr2->interp != interp) &&
                  (strcmp(riPtr2->name, actualName) == 0)) {
                goto nextSuffix;
            }
          }
          RegDeleteName(regPtr, actualName);
          break;
      } else if (!ValidateName(winPtr->dispPtr, actualName, w, 1)) {
          RegDeleteName(regPtr, actualName);
          break;
      }
      nextSuffix:
      continue;
    }

    /*
     * We've now got a name to use.  Store it in the name registry and
     * in the local entry for this application, plus put it in a property
     * on the commWindow.
     */

    RegAddName(regPtr, actualName, Tk_WindowId(dispPtr->commTkwin));
    RegClose(regPtr);
    riPtr->name = (char *) ckalloc((unsigned) (strlen(actualName) + 1));
    strcpy(riPtr->name, actualName);
    if (actualName != name) {
      Tcl_DStringFree(&dString);
    }
    UpdateCommWindow(dispPtr);

    return riPtr->name;
}

/*
 *--------------------------------------------------------------
 *
 * Tk_SendCmd --
 *
 *    This procedure is invoked to process the "send" Tcl command.
 *    See the user documentation for details on what it does.
 *
 * Results:
 *    A standard Tcl result.
 *
 * Side effects:
 *    See the user documentation.
 *
 *--------------------------------------------------------------
 */

int
Tk_SendCmd(clientData, interp, argc, argv)
    ClientData clientData;          /* Information about sender (only
                               * dispPtr field is used). */
    Tcl_Interp *interp;             /* Current interpreter. */
    int argc;                       /* Number of arguments. */
    char **argv;              /* Argument strings. */
{
    TkWindow *winPtr;
    Window commWindow;
    PendingCommand pending;
    register RegisteredInterp *riPtr;
    char *destName, buffer[30];
    int result, c, async, i, firstArg;
    size_t length;
    Tk_RestrictProc *prevRestrictProc;
    ClientData prevArg;
    TkDisplay *dispPtr;
    Tcl_Time timeout;
    NameRegistry *regPtr;
    Tcl_DString request;
    Tcl_Interp *localInterp;        /* Used when the interpreter to
                                         * send the command to is within
                                         * the same process. */

    /*
     * Process options, if any.
     */

    async = 0;
    winPtr = (TkWindow *) Tk_MainWindow(interp);
    if (winPtr == NULL) {
      return TCL_ERROR;
    }
    for (i = 1; i < (argc-1); ) {
      if (argv[i][0] != '-') {
          break;
      }
      c = argv[i][1];
      length = strlen(argv[i]);
      if ((c == 'a') && (strncmp(argv[i], "-async", length) == 0)) {
          async = 1;
          i++;
      } else if ((c == 'd') && (strncmp(argv[i], "-displayof",
            length) == 0)) {
          winPtr = (TkWindow *) Tk_NameToWindow(interp, argv[i+1],
                (Tk_Window) winPtr);
          if (winPtr == NULL) {
            return TCL_ERROR;
          }
          i += 2;
      } else if (strcmp(argv[i], "--") == 0) {
          i++;
          break;
      } else {
          Tcl_AppendResult(interp, "bad option \"", argv[i],
                "\": must be -async, -displayof, or --", (char *) NULL);
          return TCL_ERROR;
      }
    }

    if (argc < (i+2)) {
      Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
            " ?options? interpName arg ?arg ...?\"", (char *) NULL);
      return TCL_ERROR;
    }
    destName = argv[i];
    firstArg = i+1;

    dispPtr = winPtr->dispPtr;
    if (dispPtr->commTkwin == NULL) {
      SendInit(interp, winPtr->dispPtr);
    }

    /*
     * See if the target interpreter is local.  If so, execute
     * the command directly without going through the X server.
     * The only tricky thing is passing the result from the target
     * interpreter to the invoking interpreter.  Watch out:  they
     * could be the same!
     */

    for (riPtr = registry; riPtr != NULL; riPtr = riPtr->nextPtr) {
      if ((riPtr->dispPtr != dispPtr)
            || (strcmp(riPtr->name, destName) != 0)) {
          continue;
      }
      Tcl_Preserve((ClientData) riPtr);
        localInterp = riPtr->interp;
        Tcl_Preserve((ClientData) localInterp);
      if (firstArg == (argc-1)) {
          result = Tcl_GlobalEval(localInterp, argv[firstArg]);
      } else {
          Tcl_DStringInit(&request);
          Tcl_DStringAppend(&request, argv[firstArg], -1);
          for (i = firstArg+1; i < argc; i++) {
            Tcl_DStringAppend(&request, " ", 1);
            Tcl_DStringAppend(&request, argv[i], -1);
          }
          result = Tcl_GlobalEval(localInterp, Tcl_DStringValue(&request));
          Tcl_DStringFree(&request);
      }
      if (interp != localInterp) {
          if (result == TCL_ERROR) {

            /*
             * An error occurred, so transfer error information from the
             * destination interpreter back to our interpreter.  Must clear
             * interp's result before calling Tcl_AddErrorInfo, since
             * Tcl_AddErrorInfo will store the interp's result in errorInfo
             * before appending riPtr's $errorInfo;  we've already got
             * everything we need in riPtr's $errorInfo.
             */

            Tcl_ResetResult(interp);
            Tcl_AddErrorInfo(interp, Tcl_GetVar2(localInterp,
                  "errorInfo", (char *) NULL, TCL_GLOBAL_ONLY));
            Tcl_SetVar2(interp, "errorCode", (char *) NULL,
                  Tcl_GetVar2(localInterp, "errorCode", (char *) NULL,
                  TCL_GLOBAL_ONLY), TCL_GLOBAL_ONLY);
          }
            if (localInterp->freeProc != TCL_STATIC) {
                interp->result = localInterp->result;
                interp->freeProc = localInterp->freeProc;
                localInterp->freeProc = TCL_STATIC;
            } else {
                Tcl_SetResult(interp, localInterp->result, TCL_VOLATILE);
            }
            Tcl_ResetResult(localInterp);
      }
      Tcl_Release((ClientData) riPtr);
        Tcl_Release((ClientData) localInterp);
      return result;
    }

    /*
     * Bind the interpreter name to a communication window.
     */

    regPtr = RegOpen(interp, winPtr->dispPtr, 0);
    commWindow = RegFindName(regPtr, destName);
    RegClose(regPtr);
    if (commWindow == None) {
      Tcl_AppendResult(interp, "no application named \"",
            destName, "\"", (char *) NULL);
      return TCL_ERROR;
    }

    /*
     * Send the command to the target interpreter by appending it to the
     * comm window in the communication window.
     */

    tkSendSerial++;
    Tcl_DStringInit(&request);
    Tcl_DStringAppend(&request, "\0c\0-n ", 6);
    Tcl_DStringAppend(&request, destName, -1);
    if (!async) {
      sprintf(buffer, "%x %d",
            (unsigned int) Tk_WindowId(dispPtr->commTkwin),
            tkSendSerial);
      Tcl_DStringAppend(&request, "\0-r ", 4);
      Tcl_DStringAppend(&request, buffer, -1);
    }
    Tcl_DStringAppend(&request, "\0-s ", 4);
    Tcl_DStringAppend(&request, argv[firstArg], -1);
    for (i = firstArg+1; i < argc; i++) {
      Tcl_DStringAppend(&request, " ", 1);
      Tcl_DStringAppend(&request, argv[i], -1);
    }
    (void) AppendPropCarefully(dispPtr->display, commWindow,
          dispPtr->commProperty, Tcl_DStringValue(&request),
          Tcl_DStringLength(&request) + 1,
          (async) ? (PendingCommand *) NULL : &pending);
    Tcl_DStringFree(&request);
    if (async) {
      /*
       * This is an asynchronous send:  return immediately without
       * waiting for a response.
       */

      return TCL_OK;
    }

    /*
     * Register the fact that we're waiting for a command to complete
     * (this is needed by SendEventProc and by AppendErrorProc to pass
     * back the command's results).  Set up a timeout handler so that
     * we can check during long sends to make sure that the destination
     * application is still alive.
     */

    pending.serial = tkSendSerial;
    pending.dispPtr = dispPtr;
    pending.target = destName;
    pending.commWindow = commWindow;
    pending.interp = interp;
    pending.result = NULL;
    pending.errorInfo = NULL;
    pending.errorCode = NULL;
    pending.gotResponse = 0;
    pending.nextPtr = pendingCommands;
    pendingCommands = &pending;

    /*
     * Enter a loop processing X events until the result comes
     * in or the target is declared to be dead.  While waiting
     * for a result, look only at send-related events so that
     * the send is synchronous with respect to other events in
     * the application.
     */

    prevRestrictProc = Tk_RestrictEvents(SendRestrictProc,
          (ClientData) NULL, &prevArg);
    TclpGetTime(&timeout);
    timeout.sec += 2;
    while (!pending.gotResponse) {
      if (!TkUnixDoOneXEvent(&timeout)) {
          /*
           * An unusually long amount of time has elapsed during the
           * processing of a sent command.  Check to make sure that the
           * target application still exists.  If it does, reset the timeout.
           */

          if (!ValidateName(pending.dispPtr, pending.target,
                pending.commWindow, 0)) {
            char *msg;
            if (ValidateName(pending.dispPtr, pending.target,
                  pending.commWindow, 1)) {
                msg = "target application died or uses a Tk version before 4.0";
            } else {
                msg = "target application died";
            }
            pending.code = TCL_ERROR;
            pending.result = (char *) ckalloc((unsigned) (strlen(msg) + 1));
            strcpy(pending.result, msg);
            pending.gotResponse = 1;
          } else {
            TclpGetTime(&timeout);
            timeout.sec += 2;
          }
      }
    }
    (void) Tk_RestrictEvents(prevRestrictProc, prevArg, &prevArg);

    /*
     * Unregister the information about the pending command
     * and return the result.
     */

    if (pendingCommands != &pending) {
      panic("Tk_SendCmd: corrupted send stack");
    }
    pendingCommands = pending.nextPtr;
    if (pending.errorInfo != NULL) {
      /*
       * Special trick: must clear the interp's result before calling
       * Tcl_AddErrorInfo, since Tcl_AddErrorInfo will store the interp's
       * result in errorInfo before appending pending.errorInfo;  we've
       * already got everything we need in pending.errorInfo.
       */

      Tcl_ResetResult(interp);
      Tcl_AddErrorInfo(interp, pending.errorInfo);
      ckfree(pending.errorInfo);
    }
    if (pending.errorCode != NULL) {
      Tcl_SetVar2(interp, "errorCode", (char *) NULL, pending.errorCode,
            TCL_GLOBAL_ONLY);
      ckfree(pending.errorCode);
    }
    Tcl_SetResult(interp, pending.result, TCL_DYNAMIC);
    return pending.code;
}

/*
 *----------------------------------------------------------------------
 *
 * TkGetInterpNames --
 *
 *    This procedure is invoked to fetch a list of all the
 *    interpreter names currently registered for the display
 *    of a particular window.
 *
 * Results:
 *    A standard Tcl return value.  Interp->result will be set
 *    to hold a list of all the interpreter names defined for
 *    tkwin's display.  If an error occurs, then TCL_ERROR
 *    is returned and interp->result will hold an error message.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

int
TkGetInterpNames(interp, tkwin)
    Tcl_Interp *interp;       /* Interpreter for returning a result. */
    Tk_Window tkwin;          /* Window whose display is to be used
                         * for the lookup. */
{
    TkWindow *winPtr = (TkWindow *) tkwin;
    char *p, *entry, *entryName;
    NameRegistry *regPtr;
    Window commWindow;
    int count;
    unsigned int id;

    /*
     * Read the registry property, then scan through all of its entries.
     * Validate each entry to be sure that its application still exists.
     */

    regPtr = RegOpen(interp, winPtr->dispPtr, 1);
    for (p = regPtr->property; (p-regPtr->property) < (int) regPtr->propLength; ) {
      entry = p;
      if (sscanf(p,  "%x",(unsigned int *) &id) != 1) {
          commWindow =  None;
      } else {
          commWindow = id;
      }
      while ((*p != 0) && (!isspace(UCHAR(*p)))) {
          p++;
      }
      if (*p != 0) {
          p++;
      }
      entryName = p;
      while (*p != 0) {
          p++;
      }
      p++;
      if (ValidateName(winPtr->dispPtr, entryName, commWindow, 1)) {
          /*
           * The application still exists; add its name to the result.
           */

          Tcl_AppendElement(interp, entryName);
      } else {
          /*
           * This name is bogus (perhaps the application died without
           * cleaning up its entry in the registry?).  Delete the name.
           */

          count = regPtr->propLength - (p - regPtr->property);
          if (count > 0)  {
            char *src, *dst;

            for (src = p, dst = entry; count > 0; src++, dst++, count--) {
                *dst = *src;
            }
          }
          regPtr->propLength -= p - entry;
          regPtr->modified = 1;
          p = entry;
      }
    }
    RegClose(regPtr);
    return TCL_OK;
}

/*
 *--------------------------------------------------------------
 *
 * SendInit --
 *
 *    This procedure is called to initialize the
 *    communication channels for sending commands and
 *    receiving results.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Sets up various data structures and windows.
 *
 *--------------------------------------------------------------
 */

static int
SendInit(interp, dispPtr)
    Tcl_Interp *interp;       /* Interpreter to use for error reporting
                         * (no errors are ever returned, but the
                         * interpreter is needed anyway). */
    TkDisplay *dispPtr;       /* Display to initialize. */
{
    XSetWindowAttributes atts;

    /*
     * Create the window used for communication, and set up an
     * event handler for it.
     */

    dispPtr->commTkwin = Tk_CreateWindow(interp, (Tk_Window) NULL,
          "_comm", DisplayString(dispPtr->display));
    if (dispPtr->commTkwin == NULL) {
      panic("Tk_CreateWindow failed in SendInit!");
    }
    atts.override_redirect = True;
    Tk_ChangeWindowAttributes(dispPtr->commTkwin,
          CWOverrideRedirect, &atts);
    Tk_CreateEventHandler(dispPtr->commTkwin, PropertyChangeMask,
          SendEventProc, (ClientData) dispPtr);
    Tk_MakeWindowExist(dispPtr->commTkwin);

    /*
     * Get atoms used as property names.
     */

    dispPtr->commProperty = Tk_InternAtom(dispPtr->commTkwin, "Comm");
    dispPtr->registryProperty = Tk_InternAtom(dispPtr->commTkwin,
          "InterpRegistry");
    dispPtr->appNameProperty = Tk_InternAtom(dispPtr->commTkwin,
          "TK_APPLICATION");

    return TCL_OK;
}

/*
 *--------------------------------------------------------------
 *
 * SendEventProc --
 *
 *    This procedure is invoked automatically by the toolkit
 *    event manager when a property changes on the communication
 *    window.  This procedure reads the property and handles
 *    command requests and responses.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    If there are command requests in the property, they
 *    are executed.  If there are responses in the property,
 *    their information is saved for the (ostensibly waiting)
 *    "send" commands. The property is deleted.
 *
 *--------------------------------------------------------------
 */

static void
SendEventProc(clientData, eventPtr)
    ClientData clientData;    /* Display information. */    
    XEvent *eventPtr;         /* Information about event. */
{
    TkDisplay *dispPtr = (TkDisplay *) clientData;
    char *propInfo;
    register char *p;
    int result, actualFormat;
    unsigned long numItems, bytesAfter;
    Atom actualType;
    Tcl_Interp *remoteInterp; /* Interp in which to execute the command. */

    if ((eventPtr->xproperty.atom != dispPtr->commProperty)
          || (eventPtr->xproperty.state != PropertyNewValue)) {
      return;
    }

    /*
     * Read the comm property and delete it.
     */

    propInfo = NULL;
    result = XGetWindowProperty(dispPtr->display,
          Tk_WindowId(dispPtr->commTkwin),
          dispPtr->commProperty, 0, MAX_PROP_WORDS, True,
          XA_STRING, &actualType, &actualFormat,
          &numItems, &bytesAfter, (unsigned char **) &propInfo);

    /*
     * If the property doesn't exist or is improperly formed
     * then ignore it.
     */

    if ((result != Success) || (actualType != XA_STRING)
          || (actualFormat != 8)) {
      if (propInfo != NULL) {
          XFree(propInfo);
      }
      return;
    }

    /*
     * Several commands and results could arrive in the property at
     * one time;  each iteration through the outer loop handles a
     * single command or result.
     */

    for (p = propInfo; (p-propInfo) < (int) numItems; ) {
      /*
       * Ignore leading NULLs; each command or result starts with a
       * NULL so that no matter how badly formed a preceding command
       * is, we'll be able to tell that a new command/result is
       * starting.
       */

      if (*p == 0) {
          p++;
          continue;
      }

      if ((*p == 'c') && (p[1] == 0)) {
          Window commWindow;
          char *interpName, *script, *serial, *end;
          Tcl_DString reply;
          RegisteredInterp *riPtr;

          /*
           *----------------------------------------------------------
           * This is an incoming command from some other application.
           * Iterate over all of its options.  Stop when we reach
           * the end of the property or something that doesn't look
           * like an option.
           *----------------------------------------------------------
           */

          p += 2;
          interpName = NULL;
          commWindow = None;
          serial = "";
          script = NULL;
          while (((p-propInfo) < (int) numItems) && (*p == '-')) {
            switch (p[1]) {
                case 'r':
                  commWindow = (Window) strtoul(p+2, &end, 16);
                  if ((end == p+2) || (*end != ' ')) {
                      commWindow = None;
                  } else {
                      p = serial = end+1;
                  }
                  break;
                case 'n':
                  if (p[2] == ' ') {
                      interpName = p+3;
                  }
                  break;
                case 's':
                  if (p[2] == ' ') {
                      script = p+3;
                  }
                  break;
            }
            while (*p != 0) {
                p++;
            }
            p++;
          }

          if ((script == NULL) || (interpName == NULL)) {
            continue;
          }

          /*
           * Initialize the result property, so that we're ready at any
           * time if we need to return an error.
           */

          if (commWindow != None) {
            Tcl_DStringInit(&reply);
            Tcl_DStringAppend(&reply, "\0r\0-s ", 6);
            Tcl_DStringAppend(&reply, serial, -1);
            Tcl_DStringAppend(&reply, "\0-r ", 4);
          }

          if (!ServerSecure(dispPtr)) {
            if (commWindow != None) {
                Tcl_DStringAppend(&reply, "X server insecure (must use xauth-style authorization); command ignored", -1);
            }
            result = TCL_ERROR;
            goto returnResult;
          }

          /*
           * Locate the application, then execute the script.
           */

          for (riPtr = registry; ; riPtr = riPtr->nextPtr) {
            if (riPtr == NULL) {
                if (commWindow != None) {
                  Tcl_DStringAppend(&reply,
                        "receiver never heard of interpreter \"", -1);
                  Tcl_DStringAppend(&reply, interpName, -1);
                  Tcl_DStringAppend(&reply, "\"", 1);
                }
                result = TCL_ERROR;
                goto returnResult;
            }
            if (strcmp(riPtr->name, interpName) == 0) {
                break;
            }
          }
          Tcl_Preserve((ClientData) riPtr);

            /*
             * We must protect the interpreter because the script may
             * enter another event loop, which might call Tcl_DeleteInterp.
             */

            remoteInterp = riPtr->interp;
            Tcl_Preserve((ClientData) remoteInterp);

            result = Tcl_GlobalEval(remoteInterp, script);

            /*
             * The call to Tcl_Release may have released the interpreter
             * which will cause the "send" command for that interpreter
             * to be deleted. The command deletion callback will set the
             * riPtr->interp field to NULL, hence the check below for NULL.
             */

          if (commWindow != None) {
            Tcl_DStringAppend(&reply, remoteInterp->result, -1);
            if (result == TCL_ERROR) {
                char *varValue;
    
                varValue = Tcl_GetVar2(remoteInterp, "errorInfo",
                      (char *) NULL, TCL_GLOBAL_ONLY);
                if (varValue != NULL) {
                  Tcl_DStringAppend(&reply, "\0-i ", 4);
                  Tcl_DStringAppend(&reply, varValue, -1);
                }
                varValue = Tcl_GetVar2(remoteInterp, "errorCode",
                      (char *) NULL, TCL_GLOBAL_ONLY);
                if (varValue != NULL) {
                  Tcl_DStringAppend(&reply, "\0-e ", 4);
                  Tcl_DStringAppend(&reply, varValue, -1);
                }
            }
          }
            Tcl_Release((ClientData) remoteInterp);
          Tcl_Release((ClientData) riPtr);

          /*
           * Return the result to the sender if a commWindow was
           * specified (if none was specified then this is an asynchronous
           * call).  Right now reply has everything but the completion
           * code, but it needs the NULL to terminate the current option.
           */

          returnResult:
          if (commWindow != None) {
            if (result != TCL_OK) {
                char buffer[20];
    
                sprintf(buffer, "%d", result);
                Tcl_DStringAppend(&reply, "\0-c ", 4);
                Tcl_DStringAppend(&reply, buffer, -1);
            }
            (void) AppendPropCarefully(dispPtr->display, commWindow,
                  dispPtr->commProperty, Tcl_DStringValue(&reply),
                  Tcl_DStringLength(&reply) + 1,
                  (PendingCommand *) NULL);
            XFlush(dispPtr->display);
            Tcl_DStringFree(&reply);
          }
      } else if ((*p == 'r') && (p[1] == 0)) {
          int serial, code, gotSerial;
          char *errorInfo, *errorCode, *resultString;
          PendingCommand *pcPtr;

          /*
           *----------------------------------------------------------
           * This is a reply to some command that we sent out.  Iterate
           * over all of its options.  Stop when we reach the end of the
           * property or something that doesn't look like an option.
           *----------------------------------------------------------
           */

          p += 2;
          code = TCL_OK;
          gotSerial = 0;
          errorInfo = NULL;
          errorCode = NULL;
          resultString = "";
          while (((p-propInfo) < (int) numItems) && (*p == '-')) {
            switch (p[1]) {
                case 'c':
                  if (sscanf(p+2, " %d", &code) != 1) {
                      code = TCL_OK;
                  }
                  break;
                case 'e':
                  if (p[2] == ' ') {
                      errorCode = p+3;
                  }
                  break;
                case 'i':
                  if (p[2] == ' ') {
                      errorInfo = p+3;
                  }
                  break;
                case 'r':
                  if (p[2] == ' ') {
                      resultString = p+3;
                  }
                  break;
                case 's':
                  if (sscanf(p+2, " %d", &serial) == 1) {
                      gotSerial = 1;
                  }
                  break;
            }
            while (*p != 0) {
                p++;
            }
            p++;
          }

          if (!gotSerial) {
            continue;
          }

          /*
           * Give the result information to anyone who's
           * waiting for it.
           */

          for (pcPtr = pendingCommands; pcPtr != NULL;
                pcPtr = pcPtr->nextPtr) {
            if ((serial != pcPtr->serial) || (pcPtr->result != NULL)) {
                continue;
            }
            pcPtr->code = code;
            if (resultString != NULL) {
                pcPtr->result = (char *) ckalloc((unsigned)
                      (strlen(resultString) + 1));
                strcpy(pcPtr->result, resultString);
            }
            if (code == TCL_ERROR) {
                if (errorInfo != NULL) {
                  pcPtr->errorInfo = (char *) ckalloc((unsigned)
                        (strlen(errorInfo) + 1));
                  strcpy(pcPtr->errorInfo, errorInfo);
                }
                if (errorCode != NULL) {
                  pcPtr->errorCode = (char *) ckalloc((unsigned)
                        (strlen(errorCode) + 1));
                  strcpy(pcPtr->errorCode, errorCode);
                }
            }
            pcPtr->gotResponse = 1;
            break;
          }
      } else {
          /*
           * Didn't recognize this thing.  Just skip through the next
           * null character and try again.
           */

          while (*p != 0) {
            p++;
          }
          p++;
      }
    }
    XFree(propInfo);
}

/*
 *--------------------------------------------------------------
 *
 * AppendPropCarefully --
 *
 *    Append a given property to a given window, but set up
 *    an X error handler so that if the append fails this
 *    procedure can return an error code rather than having
 *    Xlib panic.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    The given property on the given window is appended to.
 *    If this operation fails and if pendingPtr is non-NULL,
 *    then the pending operation is marked as complete with
 *    an error.
 *
 *--------------------------------------------------------------
 */

static void
AppendPropCarefully(display, window, property, value, length, pendingPtr)
    Display *display;         /* Display on which to operate. */
    Window window;            /* Window whose property is to
                         * be modified. */
    Atom property;            /* Name of property. */
    char *value;        /* Characters to append to property. */
    int length;               /* Number of bytes to append. */
    PendingCommand *pendingPtr;     /* Pending command to mark complete
                         * if an error occurs during the
                         * property op.  NULL means just
                         * ignore the error. */
{
    Tk_ErrorHandler handler;

    handler = Tk_CreateErrorHandler(display, -1, -1, -1, AppendErrorProc,
      (ClientData) pendingPtr);
    XChangeProperty(display, window, property, XA_STRING, 8,
          PropModeAppend, (unsigned char *) value, length);
    Tk_DeleteErrorHandler(handler);
}

/*
 * The procedure below is invoked if an error occurs during
 * the XChangeProperty operation above.
 */

      /* ARGSUSED */
static int
AppendErrorProc(clientData, errorPtr)
    ClientData clientData;    /* Command to mark complete, or NULL. */
    XErrorEvent *errorPtr;    /* Information about error. */
{
    PendingCommand *pendingPtr = (PendingCommand *) clientData;
    register PendingCommand *pcPtr;

    if (pendingPtr == NULL) {
      return 0;
    }

    /*
     * Make sure this command is still pending.
     */

    for (pcPtr = pendingCommands; pcPtr != NULL;
          pcPtr = pcPtr->nextPtr) {
      if ((pcPtr == pendingPtr) && (pcPtr->result == NULL)) {
          pcPtr->result = (char *) ckalloc((unsigned)
                (strlen(pcPtr->target) + 50));
          sprintf(pcPtr->result, "no application named \"%s\"",
                pcPtr->target);
          pcPtr->code = TCL_ERROR;
          pcPtr->gotResponse = 1;
          break;
      }
    }
    return 0;
}

/*
 *--------------------------------------------------------------
 *
 * DeleteProc --
 *
 *    This procedure is invoked by Tcl when the "send" command
 *    is deleted in an interpreter.  It unregisters the interpreter.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    The interpreter given by riPtr is unregistered.
 *
 *--------------------------------------------------------------
 */

static void
DeleteProc(clientData)
    ClientData clientData;    /* Info about registration, passed
                         * as ClientData. */
{
    RegisteredInterp *riPtr = (RegisteredInterp *) clientData;
    register RegisteredInterp *riPtr2;
    NameRegistry *regPtr;

    regPtr = RegOpen(riPtr->interp, riPtr->dispPtr, 1);
    RegDeleteName(regPtr, riPtr->name);
    RegClose(regPtr);

    if (registry == riPtr) {
      registry = riPtr->nextPtr;
    } else {
      for (riPtr2 = registry; riPtr2 != NULL;
            riPtr2 = riPtr2->nextPtr) {
          if (riPtr2->nextPtr == riPtr) {
            riPtr2->nextPtr = riPtr->nextPtr;
            break;
          }
      }
    }
    ckfree((char *) riPtr->name);
    riPtr->interp = NULL;
    UpdateCommWindow(riPtr->dispPtr);
    Tcl_EventuallyFree((ClientData) riPtr, TCL_DYNAMIC);
}

/*
 *----------------------------------------------------------------------
 *
 * SendRestrictProc --
 *
 *    This procedure filters incoming events when a "send" command
 *    is outstanding.  It defers all events except those containing
 *    send commands and results.
 *
 * Results:
 *    False is returned except for property-change events on a
 *    commWindow.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

    /* ARGSUSED */
static Tk_RestrictAction
SendRestrictProc(clientData, eventPtr)
    ClientData clientData;          /* Not used. */
    register XEvent *eventPtr;            /* Event that just arrived. */
{
    TkDisplay *dispPtr;

    if (eventPtr->type != PropertyNotify) {
      return TK_DEFER_EVENT;
    }
    for (dispPtr = tkDisplayList; dispPtr != NULL; dispPtr = dispPtr->nextPtr) {
      if ((eventPtr->xany.display == dispPtr->display)
            && (eventPtr->xproperty.window
            == Tk_WindowId(dispPtr->commTkwin))) {
          return TK_PROCESS_EVENT;
      }
    }
    return TK_DEFER_EVENT;
}

/*
 *----------------------------------------------------------------------
 *
 * UpdateCommWindow --
 *
 *    This procedure updates the list of application names stored
 *    on our commWindow.  It is typically called when interpreters
 *    are registered and unregistered.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    The TK_APPLICATION property on the comm window is updated.
 *
 *----------------------------------------------------------------------
 */

static void
UpdateCommWindow(dispPtr)
    TkDisplay *dispPtr;       /* Display whose commWindow is to be
                         * updated. */
{
    Tcl_DString names;
    RegisteredInterp *riPtr;

    Tcl_DStringInit(&names);
    for (riPtr = registry; riPtr != NULL; riPtr = riPtr->nextPtr) {
      Tcl_DStringAppendElement(&names, riPtr->name);
    }
    XChangeProperty(dispPtr->display, Tk_WindowId(dispPtr->commTkwin),
          dispPtr->appNameProperty, XA_STRING, 8, PropModeReplace,
          (unsigned char *) Tcl_DStringValue(&names),
          Tcl_DStringLength(&names));
    Tcl_DStringFree(&names);
}

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