path: root/unix/tkUnixSelect.c

/* 
 * tkUnixSelect.c --
 *
 *	This file contains X specific routines for manipulating 
 *	selections.
 *
 * Copyright (c) 1995-1997 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: tkUnixSelect.c,v 1.10 2002/09/30 13:42:26 dkf Exp $
 */

#include "tkInt.h"
#include "tkSelect.h"

typedef struct ConvertInfo {
    int offset;			/* The starting byte offset into the selection
				 * for the next chunk; -1 means all data has
				 * been transferred for this conversion. -2
				 * means only the final zero-length transfer
				 * still has to be done.  Otherwise it is the
				 * offset of the next chunk of data to
				 * transfer. */
    Tcl_EncodingState state;	/* The encoding state needed across chunks. */
    char buffer[TCL_UTF_MAX];	/* A buffer to hold part of a UTF character
				 * that is split across chunks.*/
} ConvertInfo;

/*
 * When handling INCR-style selection retrievals, the selection owner
 * uses the following data structure to communicate between the
 * ConvertSelection procedure and TkSelPropProc.
 */

typedef struct IncrInfo {
    TkWindow *winPtr;		/* Window that owns selection. */
    Atom selection;		/* Selection that is being retrieved. */
    Atom *multAtoms;		/* Information about conversions to
				 * perform:  one or more pairs of
				 * (target, property).  This either
				 * points to a retrieved  property (for
				 * MULTIPLE retrievals) or to a static
				 * array. */
    unsigned long numConversions;
				/* Number of entries in converts (same as
				 * # of pairs in multAtoms). */
    ConvertInfo *converts;	/* One entry for each pair in multAtoms.
				 * This array is malloc-ed. */
    char **tempBufs;		/* One pointer for each pair in multAtoms;
				 * each pointer is either NULL, or it points
				 * to a small bit of character data that was
				 * left over from the previous chunk. */
    Tcl_EncodingState *state;	/* One state info per pair in multAtoms:
				 * State info for encoding conversions
				 * that span multiple buffers. */
    int *flags;			/* One state flag per pair in multAtoms:
				 * Encoding flags, set to TCL_ENCODING_START
				 * at the beginning of an INCR transfer. */
    int numIncrs;		/* Number of entries in converts that
				 * aren't -1 (i.e. # of INCR-mode transfers
				 * not yet completed). */
    Tcl_TimerToken timeout;	/* Token for timer procedure. */
    int idleTime;		/* Number of seconds since we heard
				 * anything from the selection
				 * requestor. */
    Window reqWindow;		/* Requestor's window id. */
    Time time;			/* Timestamp corresponding to
				 * selection at beginning of request;
				 * used to abort transfer if selection
				 * changes. */
    struct IncrInfo *nextPtr;	/* Next in list of all INCR-style
				 * retrievals currently pending. */
} IncrInfo;


typedef struct ThreadSpecificData {
    IncrInfo *pendingIncrs;     /* List of all incr structures
				 * currently active. */
} ThreadSpecificData;
static Tcl_ThreadDataKey dataKey;

/*
 * Largest property that we'll accept when sending or receiving the
 * selection:
 */

#define MAX_PROP_WORDS 100000

static TkSelRetrievalInfo *pendingRetrievals = NULL;
				/* List of all retrievals currently
				 * being waited for. */

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

static void		ConvertSelection _ANSI_ARGS_((TkWindow *winPtr,
			    XSelectionRequestEvent *eventPtr));
static void		IncrTimeoutProc _ANSI_ARGS_((ClientData clientData));
static char *		SelCvtFromX _ANSI_ARGS_((long *propPtr, int numValues,
			    Atom type, Tk_Window tkwin));
static long *		SelCvtToX _ANSI_ARGS_((char *string, Atom type,
			    Tk_Window tkwin, int *numLongsPtr));
static int		SelectionSize _ANSI_ARGS_((TkSelHandler *selPtr));
static void		SelRcvIncrProc _ANSI_ARGS_((ClientData clientData,
			    XEvent *eventPtr));
static void		SelTimeoutProc _ANSI_ARGS_((ClientData clientData));

/*
 *----------------------------------------------------------------------
 *
 * TkSelGetSelection --
 *
 *	Retrieve the specified selection from another process.
 *
 * Results:
 *	The return value is a standard Tcl return value.
 *	If an error occurs (such as no selection exists)
 *	then an error message is left in the interp's result.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
TkSelGetSelection(interp, tkwin, selection, target, proc, clientData)
    Tcl_Interp *interp;		/* Interpreter to use for reporting
				 * errors. */
    Tk_Window tkwin;		/* Window on whose behalf to retrieve
				 * the selection (determines display
				 * from which to retrieve). */
    Atom selection;		/* Selection to retrieve. */
    Atom target;		/* Desired form in which selection
				 * is to be returned. */
    Tk_GetSelProc *proc;	/* Procedure to call to process the
				 * selection, once it has been retrieved. */
    ClientData clientData;	/* Arbitrary value to pass to proc. */
{
    TkSelRetrievalInfo retr;
    TkWindow *winPtr = (TkWindow *) tkwin;
    TkDisplay *dispPtr = winPtr->dispPtr;

    /*
     * The selection is owned by some other process.  To
     * retrieve it, first record information about the retrieval
     * in progress.  Use an internal window as the requestor.
     */

    retr.interp = interp;
    if (dispPtr->clipWindow == NULL) {
	int result;

	result = TkClipInit(interp, dispPtr);
	if (result != TCL_OK) {
	    return result;
	}
    }
    retr.winPtr = (TkWindow *) dispPtr->clipWindow;
    retr.selection = selection;
    retr.property = selection;
    retr.target = target;
    retr.proc = proc;
    retr.clientData = clientData;
    retr.result = -1;
    retr.idleTime = 0;
    retr.encFlags = TCL_ENCODING_START;
    retr.nextPtr = pendingRetrievals;
    Tcl_DStringInit(&retr.buf);
    pendingRetrievals = &retr;

    /*
     * Initiate the request for the selection.  Note:  can't use
     * TkCurrentTime for the time.  If we do, and this application hasn't
     * received any X events in a long time, the current time will be way
     * in the past and could even predate the time when the selection was
     * made;  if this happens, the request will be rejected.
     */

    XConvertSelection(winPtr->display, retr.selection, retr.target,
	    retr.property, retr.winPtr->window, CurrentTime);

    /*
     * Enter a loop processing X events until the selection
     * has been retrieved and processed.  If no response is
     * received within a few seconds, then timeout.
     */

    retr.timeout = Tcl_CreateTimerHandler(1000, SelTimeoutProc,
	    (ClientData) &retr);
    while (retr.result == -1) {
	Tcl_DoOneEvent(0);
    }
    Tcl_DeleteTimerHandler(retr.timeout);

    /*
     * Unregister the information about the selection retrieval
     * in progress.
     */

    if (pendingRetrievals == &retr) {
	pendingRetrievals = retr.nextPtr;
    } else {
	TkSelRetrievalInfo *retrPtr;

	for (retrPtr = pendingRetrievals; retrPtr != NULL;
		retrPtr = retrPtr->nextPtr) {
	    if (retrPtr->nextPtr == &retr) {
		retrPtr->nextPtr = retr.nextPtr;
		break;
	    }
	}
    }
    Tcl_DStringFree(&retr.buf);
    return retr.result;
}

/*
 *----------------------------------------------------------------------
 *
 * TkSelPropProc --
 *
 *	This procedure is invoked when property-change events
 *	occur on windows not known to the toolkit.  Its function
 *	is to implement the sending side of the INCR selection
 *	retrieval protocol when the selection requestor deletes
 *	the property containing a part of the selection.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If the property that is receiving the selection was just
 *	deleted, then a new piece of the selection is fetched and
 *	placed in the property, until eventually there's no more
 *	selection to fetch.
 *
 *----------------------------------------------------------------------
 */

void
TkSelPropProc(eventPtr)
    register XEvent *eventPtr;		/* X PropertyChange event. */
{
    register IncrInfo *incrPtr;
    register TkSelHandler *selPtr;
    int i, length, numItems;
    Atom target, formatType;
    long buffer[TK_SEL_WORDS_AT_ONCE];
    TkDisplay *dispPtr = TkGetDisplay(eventPtr->xany.display);
    Tk_ErrorHandler errorHandler;
    ThreadSpecificData *tsdPtr = (ThreadSpecificData *) 
            Tcl_GetThreadData(&dataKey, sizeof(ThreadSpecificData));

    /*
     * See if this event announces the deletion of a property being
     * used for an INCR transfer.  If so, then add the next chunk of
     * data to the property.
     */

    if (eventPtr->xproperty.state != PropertyDelete) {
	return;
    }
    for (incrPtr = tsdPtr->pendingIncrs; incrPtr != NULL;
	    incrPtr = incrPtr->nextPtr) {
	if (incrPtr->reqWindow != eventPtr->xproperty.window) {
	    continue;
	}

	/*
	 * For each conversion that has been requested, handle any
	 * chunks that haven't been transmitted yet.
	 */						  

	for (i = 0; i < incrPtr->numConversions; i++) {
	    if ((eventPtr->xproperty.atom != incrPtr->multAtoms[2*i + 1])
		    || (incrPtr->converts[i].offset == -1)) {
		continue;
	    }
	    target = incrPtr->multAtoms[2*i];
	    incrPtr->idleTime = 0;

	    /*
	     * Look for a matching selection handler.
	     */

	    for (selPtr = incrPtr->winPtr->selHandlerList; ;
		    selPtr = selPtr->nextPtr) {
		if (selPtr == NULL) {
		    /*
		     * No handlers match, so mark the conversion as done.
		     */

		    incrPtr->multAtoms[2*i + 1] = None;
		    incrPtr->converts[i].offset = -1;
		    incrPtr->numIncrs --;
		    return;
		}
		if ((selPtr->target == target)
			&& (selPtr->selection == incrPtr->selection)) {
		    break;
		}
	    }

	    /*
	     * We found a handler, so get the next chunk from it.
	     */

	    formatType = selPtr->format;
	    if (incrPtr->converts[i].offset == -2) {
		/*
		 * We already got the last chunk, so send a null chunk
		 * to indicate that we are finished.
		 */

		numItems = 0;
		length = 0;
	    } else {
		TkSelInProgress ip;
		ip.selPtr = selPtr;
		ip.nextPtr = TkSelGetInProgress();
		TkSelSetInProgress(&ip);

		/*
		 * Copy any bytes left over from a partial character at the end
		 * of the previous chunk into the beginning of the buffer.
		 * Pass the rest of the buffer space into the selection
		 * handler.
		 */

		length = strlen(incrPtr->converts[i].buffer);
		strcpy((char *)buffer, incrPtr->converts[i].buffer);
			    
		numItems = (*selPtr->proc)(selPtr->clientData,
			incrPtr->converts[i].offset,
			((char *) buffer) + length,
			TK_SEL_BYTES_AT_ONCE - length);
		TkSelSetInProgress(ip.nextPtr);
		if (ip.selPtr == NULL) {
		    /*
		     * The selection handler deleted itself.
		     */

		    return;
		}
		if (numItems < 0) {
		    numItems = 0;
		}
		numItems += length;
		if (numItems > TK_SEL_BYTES_AT_ONCE) {
		    panic("selection handler returned too many bytes");
		}
	    }
	    ((char *) buffer)[numItems] = 0;

	    errorHandler = Tk_CreateErrorHandler(eventPtr->xproperty.display,
		    -1, -1, -1, (int (*)()) NULL, (ClientData) NULL);
	    /*
	     * Encode the data using the proper format for each type.
	     */

	    if ((formatType == XA_STRING)
		    || (dispPtr && formatType==dispPtr->compoundTextAtom)) {
		Tcl_DString ds;
		int encodingCvtFlags;
		int srcLen, dstLen, result, srcRead, dstWrote, soFar;
		char *src, *dst;
		Tcl_Encoding encoding;

		/*
		 * Set up the encoding state based on the format and whether
		 * this is the first and/or last chunk.
		 */

		encodingCvtFlags = 0;
		if (incrPtr->converts[i].offset == 0) {
		    encodingCvtFlags |= TCL_ENCODING_START;
		}
		if (numItems < TK_SEL_BYTES_AT_ONCE) {
		    encodingCvtFlags |= TCL_ENCODING_END;
		}
		if (formatType == XA_STRING) {
		    encoding = Tcl_GetEncoding(NULL, "iso8859-1");
		} else {
		    encoding = Tcl_GetEncoding(NULL, "iso2022");
		}

		/*
		 * Now convert the data.
		 */

		src = (char *)buffer;
		srcLen = numItems;
		Tcl_DStringInit(&ds);
		dst = Tcl_DStringValue(&ds);
		dstLen = ds.spaceAvl - 1;


		/*
		 * Now convert the data, growing the destination buffer
		 * as needed. 
		 */

		while (1) {
		    result = Tcl_UtfToExternal(NULL, encoding,
			    src, srcLen, encodingCvtFlags,
			    &incrPtr->converts[i].state,
			    dst, dstLen, &srcRead, &dstWrote, NULL);
		    soFar = dst + dstWrote - Tcl_DStringValue(&ds);
		    encodingCvtFlags &= ~TCL_ENCODING_START;
		    src += srcRead;
		    srcLen -= srcRead;
		    if (result != TCL_CONVERT_NOSPACE) {
			Tcl_DStringSetLength(&ds, soFar);
			break;
		    }
		    if (Tcl_DStringLength(&ds) == 0) {
			Tcl_DStringSetLength(&ds, dstLen);
		    }
		    Tcl_DStringSetLength(&ds, 2 * Tcl_DStringLength(&ds) + 1);
		    dst = Tcl_DStringValue(&ds) + soFar;
		    dstLen = Tcl_DStringLength(&ds) - soFar - 1;
		}
		Tcl_DStringSetLength(&ds, soFar);

		if (encoding) {
		    Tcl_FreeEncoding(encoding);
		}

		/*
		 * Set the property to the encoded string value.
		 */

		XChangeProperty(eventPtr->xproperty.display,
			eventPtr->xproperty.window, eventPtr->xproperty.atom,
			formatType, 8, PropModeReplace,
			(unsigned char *) Tcl_DStringValue(&ds),
			Tcl_DStringLength(&ds));

		/*
		 * Preserve any left-over bytes.
		 */

		if (srcLen > TCL_UTF_MAX) {
		    panic("selection conversion left too many bytes unconverted");
		}
		memcpy(incrPtr->converts[i].buffer, src, (size_t) srcLen+1);
		Tcl_DStringFree(&ds);
	    } else if (dispPtr && formatType==dispPtr->utf8Atom) {
		/*
		 * Detect if the last character was a complete UTF-8
		 * character; if not, it is not a good idea to send it
		 * to the remote end as there's no telling whether the
		 * other side will be able to digest partial
		 * characters.
		 *
		 * Note that utfLength is calculated and then potentially
		 * recalculated...
		 */
		CONST char *utfBuffer = (CONST char *) buffer;
		CONST char *lastChar =
			Tcl_UtfPrev(utfBuffer+numItems, utfBuffer);
		int utfLength = lastChar-utfBuffer;

		if (numItems-utfLength > TCL_UTF_MAX) {
		    panic("Tcl_UtfPrev scanned backward over more than one character");
		}
		if (!Tcl_UtfCharComplete(lastChar, numItems-utfLength)) {
		    /*
		     * numItems must not be reduced, so we need to set
		     * the length of the bits we want to subtract off
		     * it here.  Horrid!
		     */
		    length = numItems - utfLength;
		} else {
		    /*
		     * We want to shovel all the data we've got across
		     */
		    utfLength = numItems;
		}

		XChangeProperty(eventPtr->xproperty.display,
			eventPtr->xproperty.window, eventPtr->xproperty.atom,
			formatType, 8, PropModeReplace,
			(unsigned char *) utfBuffer, utfLength);
	    } else {
		/*
		 * Set the property to the encoded string value.
		 */

		char *propPtr = (char *) SelCvtToX((char *) buffer,
			formatType, (Tk_Window) incrPtr->winPtr,
			&numItems);

		XChangeProperty(eventPtr->xproperty.display,
			eventPtr->xproperty.window, eventPtr->xproperty.atom,
			formatType, 32, PropModeReplace,
			(unsigned char *) propPtr, numItems);
		ckfree(propPtr);
	    }
	    Tk_DeleteErrorHandler(errorHandler);

	    /*
	     * Compute the next offset value.  If this was the last chunk,
	     * then set the offset to -2.  If this was an empty chunk,
	     * then set the offset to -1 to indicate we are done.
	     */

	    if (numItems < TK_SEL_BYTES_AT_ONCE) {
		if (numItems <= 0) {
		    incrPtr->converts[i].offset = -1;
		    incrPtr->numIncrs--;
		} else {
		    incrPtr->converts[i].offset = -2;
		}
	    } else {
		/*
		 * Advance over the selection data that was consumed
		 * this time.
		 */
 
		incrPtr->converts[i].offset += numItems - length;
	    }
	    return;
	}
    }
}

/*
 *--------------------------------------------------------------
 *
 * TkSelEventProc --
 *
 *	This procedure is invoked whenever a selection-related
 *	event occurs.  It does the lion's share of the work
 *	in implementing the selection protocol.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Lots:  depends on the type of event.
 *
 *--------------------------------------------------------------
 */

void
TkSelEventProc(tkwin, eventPtr)
    Tk_Window tkwin;		/* Window for which event was
				 * targeted. */
    register XEvent *eventPtr;	/* X event:  either SelectionClear,
				 * SelectionRequest, or
				 * SelectionNotify. */
{
    register TkWindow *winPtr = (TkWindow *) tkwin;
    TkDisplay *dispPtr = winPtr->dispPtr;
    Tcl_Interp *interp;

    /*
     * Case #1: SelectionClear events.
     */

    if (eventPtr->type == SelectionClear) {
	TkSelClearSelection(tkwin, eventPtr);
    }

    /*
     * Case #2: SelectionNotify events.  Call the relevant procedure
     * to handle the incoming selection.
     */

    if (eventPtr->type == SelectionNotify) {
	register TkSelRetrievalInfo *retrPtr;
	char *propInfo;
	Atom type;
	int format, result;
	unsigned long numItems, bytesAfter;
	Tcl_DString ds;

	for (retrPtr = pendingRetrievals; ; retrPtr = retrPtr->nextPtr) {
	    if (retrPtr == NULL) {
		return;
	    }
	    if ((retrPtr->winPtr == winPtr)
		    && (retrPtr->selection == eventPtr->xselection.selection)
		    && (retrPtr->target == eventPtr->xselection.target)
		    && (retrPtr->result == -1)) {
		if (retrPtr->property == eventPtr->xselection.property) {
		    break;
		}
		if (eventPtr->xselection.property == None) {
		    Tcl_SetResult(retrPtr->interp, (char *) NULL, TCL_STATIC);
		    Tcl_AppendResult(retrPtr->interp,
			    Tk_GetAtomName(tkwin, retrPtr->selection),
			    " selection doesn't exist or form \"",
			    Tk_GetAtomName(tkwin, retrPtr->target),
			    "\" not defined", (char *) NULL);
		    retrPtr->result = TCL_ERROR;
		    return;
		}
	    }
	}

	propInfo = NULL;
	result = XGetWindowProperty(eventPtr->xselection.display,
		eventPtr->xselection.requestor, retrPtr->property,
		0, MAX_PROP_WORDS, False, (Atom) AnyPropertyType,
		&type, &format, &numItems, &bytesAfter,
		(unsigned char **) &propInfo);
	if ((result != Success) || (type == None)) {
	    return;
	}
	if (bytesAfter != 0) {
	    Tcl_SetResult(retrPtr->interp, "selection property too large",
		TCL_STATIC);
	    retrPtr->result = TCL_ERROR;
	    XFree(propInfo);
	    return;
	}
	if ((type == XA_STRING) || (type == dispPtr->textAtom)
		|| (type == dispPtr->compoundTextAtom)) {
	    Tcl_Encoding encoding;
	    if (format != 8) {
		char buf[64 + TCL_INTEGER_SPACE];

		sprintf(buf, 
			"bad format for string selection: wanted \"8\", got \"%d\"",
			format);
		Tcl_SetResult(retrPtr->interp, buf, TCL_VOLATILE);
		retrPtr->result = TCL_ERROR;
		return;
	    }
            interp = retrPtr->interp;
            Tcl_Preserve((ClientData) interp);

	    /*
	     * Convert the X selection data into UTF before passing it
	     * to the selection callback.  Note that the COMPOUND_TEXT
	     * uses a modified iso2022 encoding, not the current system
	     * encoding.  For now we'll just blindly apply the iso2022
	     * encoding.  This is probably wrong, but it's a placeholder
	     * until we figure out what we're really supposed to do.  For
	     * STRING, we need to use Latin-1 instead.  Again, it's not
	     * really the full iso8859-1 space, but this is close enough.
	     */

	    if (type == dispPtr->compoundTextAtom) {
		encoding = Tcl_GetEncoding(NULL, "iso2022");
	    } else {
		encoding = Tcl_GetEncoding(NULL, "iso8859-1");
	    }
	    Tcl_ExternalToUtfDString(encoding, propInfo, (int)numItems, &ds);
	    if (encoding) {
		Tcl_FreeEncoding(encoding);
	    }

	    retrPtr->result = (*retrPtr->proc)(retrPtr->clientData,
		    interp, Tcl_DStringValue(&ds));
	    Tcl_DStringFree(&ds);
	    Tcl_Release((ClientData) interp);
	} else if (type == dispPtr->utf8Atom) {
	    /*
	     * The X selection data is in UTF-8 format already.
	     * We can't guarantee that propInfo is NULL-terminated,
	     * so we might have to copy the string.
	     */
	    char *propData = propInfo;

	    if (format != 8) {
		char buf[64 + TCL_INTEGER_SPACE];

		sprintf(buf, 
			"bad format for string selection: wanted \"8\", got \"%d\"",
			format);
		Tcl_SetResult(retrPtr->interp, buf, TCL_VOLATILE);
		retrPtr->result = TCL_ERROR;
		return;
	    }

	    if (propInfo[numItems] != '\0') {
		propData = ckalloc((size_t) numItems + 1);
		strcpy(propData, propInfo);
		propData[numItems] = '\0';
	    }
	    retrPtr->result = (*retrPtr->proc)(retrPtr->clientData,
		    retrPtr->interp, propData);
	    if (propData != propInfo) {
		ckfree((char *) propData);
	    }
	} else if (type == dispPtr->incrAtom) {

	    /*
	     * It's a !?#@!?!! INCR-style reception.  Arrange to receive
	     * the selection in pieces, using the ICCCM protocol, then
	     * hang around until either the selection is all here or a
	     * timeout occurs.
	     */

	    retrPtr->idleTime = 0;
	    Tk_CreateEventHandler(tkwin, PropertyChangeMask, SelRcvIncrProc,
		    (ClientData) retrPtr);
	    XDeleteProperty(Tk_Display(tkwin), Tk_WindowId(tkwin),
		    retrPtr->property);
	    while (retrPtr->result == -1) {
		Tcl_DoOneEvent(0);
	    }
	    Tk_DeleteEventHandler(tkwin, PropertyChangeMask, SelRcvIncrProc,
		    (ClientData) retrPtr);
	} else {
	    char *string;

	    if (format != 32) {
		char buf[64 + TCL_INTEGER_SPACE];

		sprintf(buf, 
			"bad format for selection: wanted \"32\", got \"%d\"",
			format);
		Tcl_SetResult(retrPtr->interp, buf, TCL_VOLATILE);
		retrPtr->result = TCL_ERROR;
		return;
	    }
	    string = SelCvtFromX((long *) propInfo, (int) numItems, type,
		    (Tk_Window) winPtr);
            interp = retrPtr->interp;
            Tcl_Preserve((ClientData) interp);
	    retrPtr->result = (*retrPtr->proc)(retrPtr->clientData,
		    interp, string);
            Tcl_Release((ClientData) interp);
	    ckfree(string);
	}
	XFree(propInfo);
	return;
    }

    /*
     * Case #3: SelectionRequest events.  Call ConvertSelection to
     * do the dirty work.
     */

    if (eventPtr->type == SelectionRequest) {
	ConvertSelection(winPtr, &eventPtr->xselectionrequest);
	return;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * SelTimeoutProc --
 *
 *	This procedure is invoked once every second while waiting for
 *	the selection to be returned.  After a while it gives up and
 *	aborts the selection retrieval.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	A new timer callback is created to call us again in another
 *	second, unless time has expired, in which case an error is
 *	recorded for the retrieval.
 *
 *----------------------------------------------------------------------
 */

static void
SelTimeoutProc(clientData)
    ClientData clientData;		/* Information about retrieval
					 * in progress. */
{
    register TkSelRetrievalInfo *retrPtr = (TkSelRetrievalInfo *) clientData;

    /*
     * Make sure that the retrieval is still in progress.  Then
     * see how long it's been since any sort of response was received
     * from the other side.
     */

    if (retrPtr->result != -1) {
	return;
    }
    retrPtr->idleTime++;
    if (retrPtr->idleTime >= 5) {

	/*
	 * Use a careful procedure to store the error message, because
	 * the result could already be partially filled in with a partial
	 * selection return.
	 */

	Tcl_SetResult(retrPtr->interp, "selection owner didn't respond",
		TCL_STATIC);
	retrPtr->result = TCL_ERROR;
    } else {
	retrPtr->timeout = Tcl_CreateTimerHandler(1000, SelTimeoutProc,
	    (ClientData) retrPtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ConvertSelection --
 *
 *	This procedure is invoked to handle SelectionRequest events.
 *	It responds to the requests, obeying the ICCCM protocols.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Properties are created for the selection requestor, and a
 *	SelectionNotify event is generated for the selection
 *	requestor.  In the event of long selections, this procedure
 *	implements INCR-mode transfers, using the ICCCM protocol.
 *
 *----------------------------------------------------------------------
 */

static void
ConvertSelection(winPtr, eventPtr)
    TkWindow *winPtr;			/* Window that received the
					 * conversion request;  may not be
					 * selection's current owner, be we
					 * set it to the current owner. */
    register XSelectionRequestEvent *eventPtr;
					/* Event describing request. */
{
    XSelectionEvent reply;		/* Used to notify requestor that
					 * selection info is ready. */
    int multiple;			/* Non-zero means a MULTIPLE request
					 * is being handled. */
    IncrInfo incr;			/* State of selection conversion. */
    Atom singleInfo[2];			/* incr.multAtoms points here except
					 * for multiple conversions. */
    int i;
    Tk_ErrorHandler errorHandler;
    TkSelectionInfo *infoPtr;
    TkSelInProgress ip;
    ThreadSpecificData *tsdPtr = (ThreadSpecificData *) 
            Tcl_GetThreadData(&dataKey, sizeof(ThreadSpecificData));

    errorHandler = Tk_CreateErrorHandler(eventPtr->display, -1, -1,-1,
	    (int (*)()) NULL, (ClientData) NULL);

    /*
     * Initialize the reply event.
     */

    reply.type = SelectionNotify;
    reply.serial = 0;
    reply.send_event = True;
    reply.display = eventPtr->display;
    reply.requestor = eventPtr->requestor;
    reply.selection = eventPtr->selection;
    reply.target = eventPtr->target;
    reply.property = eventPtr->property;
    if (reply.property == None) {
	reply.property = reply.target;
    }
    reply.time = eventPtr->time;

    for (infoPtr = winPtr->dispPtr->selectionInfoPtr; infoPtr != NULL;
	    infoPtr = infoPtr->nextPtr) {
	if (infoPtr->selection == eventPtr->selection)
	    break;
    }
    if (infoPtr == NULL) {
	goto refuse;
    }
    winPtr = (TkWindow *) infoPtr->owner;

    /*
     * Figure out which kind(s) of conversion to perform.  If handling
     * a MULTIPLE conversion, then read the property describing which
     * conversions to perform.
     */

    incr.winPtr = winPtr;
    incr.selection = eventPtr->selection;
    if (eventPtr->target != winPtr->dispPtr->multipleAtom) {
	multiple = 0;
	singleInfo[0] = reply.target;
	singleInfo[1] = reply.property;
	incr.multAtoms = singleInfo;
	incr.numConversions = 1;
    } else {
	Atom type;
	int format, result;
	unsigned long bytesAfter;

	multiple = 1;
	incr.multAtoms = NULL;
	if (eventPtr->property == None) {
	    goto refuse;
	}
	result = XGetWindowProperty(eventPtr->display,
		eventPtr->requestor, eventPtr->property,
		0, MAX_PROP_WORDS, False, XA_ATOM,
		&type, &format, &incr.numConversions, &bytesAfter,
		(unsigned char **) &incr.multAtoms);
	if ((result != Success) || (bytesAfter != 0) || (format != 32)
		|| (type == None)) {
	    if (incr.multAtoms != NULL) {
		XFree((char *) incr.multAtoms);
	    }
	    goto refuse;
	}
	incr.numConversions /= 2;		/* Two atoms per conversion. */
    }

    /*
     * Loop through all of the requested conversions, and either return
     * the entire converted selection, if it can be returned in a single
     * bunch, or return INCR information only (the actual selection will
     * be returned below).
     */

    incr.converts = (ConvertInfo *) ckalloc((unsigned)
	    (incr.numConversions*sizeof(ConvertInfo)));
    incr.numIncrs = 0;
    for (i = 0; i < incr.numConversions; i++) {
	Atom target, property, type;
	long buffer[TK_SEL_WORDS_AT_ONCE];
	register TkSelHandler *selPtr;
	int numItems, format;
	char *propPtr;

	target = incr.multAtoms[2*i];
	property = incr.multAtoms[2*i + 1];
	incr.converts[i].offset = -1;
	incr.converts[i].buffer[0] = '\0';

	for (selPtr = winPtr->selHandlerList; selPtr != NULL;
		selPtr = selPtr->nextPtr) {
	    if ((selPtr->target == target)
		    && (selPtr->selection == eventPtr->selection)) {
		break;
	    }
	}

	if (selPtr == NULL) {
	    /*
	     * Nobody seems to know about this kind of request.  If
	     * it's of a sort that we can handle without any help, do
	     * it.  Otherwise mark the request as an errror.
	     */

	    numItems = TkSelDefaultSelection(infoPtr, target, (char *) buffer,
		    TK_SEL_BYTES_AT_ONCE, &type);
	    if (numItems < 0) {
		incr.multAtoms[2*i + 1] = None;
		continue;
	    }
	} else {
	    ip.selPtr = selPtr;
	    ip.nextPtr = TkSelGetInProgress();
	    TkSelSetInProgress(&ip);
	    type = selPtr->format;
	    numItems = (*selPtr->proc)(selPtr->clientData, 0,
		    (char *) buffer, TK_SEL_BYTES_AT_ONCE);
	    TkSelSetInProgress(ip.nextPtr);
	    if ((ip.selPtr == NULL) || (numItems < 0)) {
		incr.multAtoms[2*i + 1] = None;
		continue;
	    }
	    if (numItems > TK_SEL_BYTES_AT_ONCE) {
		panic("selection handler returned too many bytes");
	    }
	    ((char *) buffer)[numItems] = '\0';
	}

	/*
	 * Got the selection;  store it back on the requestor's property.
	 */

	if (numItems == TK_SEL_BYTES_AT_ONCE) {
	    /*
	     * Selection is too big to send at once;  start an
	     * INCR-mode transfer.
	     */

	    incr.numIncrs++;
	    type = winPtr->dispPtr->incrAtom;
	    buffer[0] = SelectionSize(selPtr);
	    if (buffer[0] == 0) {
		incr.multAtoms[2*i + 1] = None;
		continue;
	    }
	    numItems = 1;
	    propPtr = (char *) buffer;
	    format = 32;
	    incr.converts[i].offset = 0;
	    XChangeProperty(reply.display, reply.requestor,
		    property, type, format, PropModeReplace,
		    (unsigned char *) propPtr, numItems);
	} else if (type == winPtr->dispPtr->utf8Atom) {
	    /*
	     * This matches selection requests of type UTF8_STRING,
	     * which allows us to pass our utf-8 information untouched.
	     */

	    XChangeProperty(reply.display, reply.requestor,
		    property, type, 8, PropModeReplace,
		    (unsigned char *) buffer, numItems);
	} else if ((type == XA_STRING)
		|| (type == winPtr->dispPtr->compoundTextAtom)) {
	    Tcl_DString ds;
	    Tcl_Encoding encoding;

	    /*
	     * STRING is Latin-1, COMPOUND_TEXT is an iso2022 variant.
	     * We need to convert the selection text into these external
	     * forms before modifying the property.
	     */

	    if (type == XA_STRING) {
		encoding = Tcl_GetEncoding(NULL, "iso8859-1");
	    } else {
		encoding = Tcl_GetEncoding(NULL, "iso2022");
	    } 
	    Tcl_UtfToExternalDString(encoding, (char*)buffer, -1, &ds);
	    XChangeProperty(reply.display, reply.requestor,
		    property, type, 8, PropModeReplace,
		    (unsigned char *) Tcl_DStringValue(&ds),
		    Tcl_DStringLength(&ds));
	    if (encoding) {
		Tcl_FreeEncoding(encoding);
	    }
	    Tcl_DStringFree(&ds);
	} else {
	    propPtr = (char *) SelCvtToX((char *) buffer,
		    type, (Tk_Window) winPtr, &numItems);
	    format = 32;
	    XChangeProperty(reply.display, reply.requestor,
		    property, type, format, PropModeReplace,
		    (unsigned char *) propPtr, numItems);
	    ckfree(propPtr);
	}
    }

    /*
     * Send an event back to the requestor to indicate that the
     * first stage of conversion is complete (everything is done
     * except for long conversions that have to be done in INCR
     * mode).
     */

    if (incr.numIncrs > 0) {
	XSelectInput(reply.display, reply.requestor, PropertyChangeMask);
	incr.timeout = Tcl_CreateTimerHandler(1000, IncrTimeoutProc,
	    (ClientData) &incr);
	incr.idleTime = 0;
	incr.reqWindow = reply.requestor;
	incr.time = infoPtr->time;
	incr.nextPtr = tsdPtr->pendingIncrs;
	tsdPtr->pendingIncrs = &incr;
    }
    if (multiple) {
	XChangeProperty(reply.display, reply.requestor, reply.property,
		XA_ATOM, 32, PropModeReplace,
		(unsigned char *) incr.multAtoms,
		(int) incr.numConversions*2);
    } else {

	/*
	 * Not a MULTIPLE request.  The first property in "multAtoms"
	 * got set to None if there was an error in conversion.
	 */

	reply.property = incr.multAtoms[1];
    }
    XSendEvent(reply.display, reply.requestor, False, 0, (XEvent *) &reply);
    Tk_DeleteErrorHandler(errorHandler);

    /*
     * Handle any remaining INCR-mode transfers.  This all happens
     * in callbacks to TkSelPropProc, so just wait until the number
     * of uncompleted INCR transfers drops to zero.
     */

    if (incr.numIncrs > 0) {
	IncrInfo *incrPtr2;

	while (incr.numIncrs > 0) {
	    Tcl_DoOneEvent(0);
	}
	Tcl_DeleteTimerHandler(incr.timeout);
	errorHandler = Tk_CreateErrorHandler(winPtr->display,
		-1, -1,-1, (int (*)()) NULL, (ClientData) NULL);
	XSelectInput(reply.display, reply.requestor, 0L);
	Tk_DeleteErrorHandler(errorHandler);
	if (tsdPtr->pendingIncrs == &incr) {
	    tsdPtr->pendingIncrs = incr.nextPtr;
	} else {
	    for (incrPtr2 = tsdPtr->pendingIncrs; incrPtr2 != NULL;
		    incrPtr2 = incrPtr2->nextPtr) {
		if (incrPtr2->nextPtr == &incr) {
		    incrPtr2->nextPtr = incr.nextPtr;
		    break;
		}
	    }
	}
    }

    /*
     * All done.  Cleanup and return.
     */

    ckfree((char *) incr.converts);
    if (multiple) {
	XFree((char *) incr.multAtoms);
    }
    return;

    /*
     * An error occurred.  Send back a refusal message.
     */

    refuse:
    reply.property = None;
    XSendEvent(reply.display, reply.requestor, False, 0, (XEvent *) &reply);
    Tk_DeleteErrorHandler(errorHandler);
    return;
}

/*
 *----------------------------------------------------------------------
 *
 * SelRcvIncrProc --
 *
 *	This procedure handles the INCR protocol on the receiving
 *	side.  It is invoked in response to property changes on
 *	the requestor's window (which hopefully are because a new
 *	chunk of the selection arrived).
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	If a new piece of selection has arrived, a procedure is
 *	invoked to deal with that piece.  When the whole selection
 *	is here, a flag is left for the higher-level procedure that
 *	initiated the selection retrieval.
 *
 *----------------------------------------------------------------------
 */

static void
SelRcvIncrProc(clientData, eventPtr)
    ClientData clientData;		/* Information about retrieval. */
    register XEvent *eventPtr;		/* X PropertyChange event. */
{
    register TkSelRetrievalInfo *retrPtr = (TkSelRetrievalInfo *) clientData;
    char *propInfo;
    Atom type;
    int format, result;
    unsigned long numItems, bytesAfter;
    Tcl_Interp *interp;

    if ((eventPtr->xproperty.atom != retrPtr->property)
	    || (eventPtr->xproperty.state != PropertyNewValue)
	    || (retrPtr->result != -1)) {
	return;
    }
    propInfo = NULL;
    result = XGetWindowProperty(eventPtr->xproperty.display,
	    eventPtr->xproperty.window, retrPtr->property, 0, MAX_PROP_WORDS,
	    True, (Atom) AnyPropertyType, &type, &format, &numItems,
	    &bytesAfter, (unsigned char **) &propInfo);
    if ((result != Success) || (type == None)) {
	return;
    }
    if (bytesAfter != 0) {
	Tcl_SetResult(retrPtr->interp, "selection property too large",
		TCL_STATIC);
	retrPtr->result = TCL_ERROR;
	goto done;
    }
    if ((type == XA_STRING)
	    || (type == retrPtr->winPtr->dispPtr->textAtom)
	    || (type == retrPtr->winPtr->dispPtr->compoundTextAtom)) {
	char *dst, *src;
	int srcLen, dstLen, srcRead, dstWrote, soFar;
	Tcl_Encoding encoding;
	Tcl_DString *dstPtr, temp;

	if (format != 8) {
	    char buf[64 + TCL_INTEGER_SPACE];
	    
	    sprintf(buf, 
		    "bad format for string selection: wanted \"8\", got \"%d\"",
		    format);
	    Tcl_SetResult(retrPtr->interp, buf, TCL_VOLATILE);
	    retrPtr->result = TCL_ERROR;
	    goto done;
	}
        interp = retrPtr->interp;
        Tcl_Preserve((ClientData) interp);

	if (type == retrPtr->winPtr->dispPtr->compoundTextAtom) {
	    encoding = Tcl_GetEncoding(NULL, "iso2022");
	} else {
	    encoding = Tcl_GetEncoding(NULL, "iso8859-1");
	}

	/*
	 * Check to see if there is any data left over from the previous
	 * chunk.  If there is, copy the old data and the new data into
	 * a new buffer.
	 */

	Tcl_DStringInit(&temp);
	if (Tcl_DStringLength(&retrPtr->buf) > 0) {
	    Tcl_DStringAppend(&temp, Tcl_DStringValue(&retrPtr->buf),
		    Tcl_DStringLength(&retrPtr->buf));
	    if (numItems > 0) {
		Tcl_DStringAppend(&temp, propInfo, (int)numItems);
	    }
	    src = Tcl_DStringValue(&temp);
	    srcLen = Tcl_DStringLength(&temp);
	} else if (numItems == 0) {
	    /*
	     * There is no new data, so we're done.
	     */

	    retrPtr->result = TCL_OK;
	    Tcl_Release((ClientData) interp);
	    goto done;
	} else {
	    src = propInfo;
	    srcLen = numItems;
	}
	
	/*
	 * Set up the destination buffer so we can use as much space as
	 * is available.
	 */

	dstPtr = &retrPtr->buf;
	dst = Tcl_DStringValue(dstPtr);
	dstLen = dstPtr->spaceAvl - 1;

	/*
	 * Now convert the data, growing the destination buffer as needed.
	 */

	while (1) {
	    result = Tcl_ExternalToUtf(NULL, encoding, src, srcLen,
		    retrPtr->encFlags, &retrPtr->encState,
		    dst, dstLen, &srcRead, &dstWrote, NULL);
	    soFar = dst + dstWrote - Tcl_DStringValue(dstPtr);
	    retrPtr->encFlags &= ~TCL_ENCODING_START;
	    src += srcRead;
	    srcLen -= srcRead;
	    if (result != TCL_CONVERT_NOSPACE) {
		Tcl_DStringSetLength(dstPtr, soFar);
		break;
	    }
	    if (Tcl_DStringLength(dstPtr) == 0) {
		Tcl_DStringSetLength(dstPtr, dstLen);
	    }
	    Tcl_DStringSetLength(dstPtr, 2 * Tcl_DStringLength(dstPtr) + 1);
	    dst = Tcl_DStringValue(dstPtr) + soFar;
	    dstLen = Tcl_DStringLength(dstPtr) - soFar - 1;
	}
	Tcl_DStringSetLength(dstPtr, soFar);

	result = (*retrPtr->proc)(retrPtr->clientData, interp,
		Tcl_DStringValue(dstPtr));
        Tcl_Release((ClientData) interp);

	/*
	 * Copy any unused data into the destination buffer so we can
	 * pick it up next time around.
	 */

	Tcl_DStringSetLength(dstPtr, 0);
	Tcl_DStringAppend(dstPtr, src, srcLen);

	Tcl_DStringFree(&temp);
	if (encoding) {
	    Tcl_FreeEncoding(encoding);
	}
	if (result != TCL_OK) {
	    retrPtr->result = result;
	}
    } else if (type == retrPtr->winPtr->dispPtr->utf8Atom) {
	/*
	 * The X selection data is in UTF-8 format already.
	 * We can't guarantee that propInfo is NULL-terminated,
	 * so we might have to copy the string.
	 */
	char *propData = propInfo;

	if (format != 8) {
	    char buf[64 + TCL_INTEGER_SPACE];
	    
	    sprintf(buf, 
		    "bad format for string selection: wanted \"8\", got \"%d\"",
		    format);
	    Tcl_SetResult(retrPtr->interp, buf, TCL_VOLATILE);
	    retrPtr->result = TCL_ERROR;
	    goto done;
	}

	/*
	 * Check for the end of the incremental transfer.
	 */
	if (numItems == 0) {
	    retrPtr->result = TCL_OK;
	    goto done;
	}

	/*
	 * Not sure if this is correct; can propInfo contain embedded
	 * NUL bytes?  Certainly not if it is coming from Tcl/Tk, but
	 * I don't remember if all other apps treat \u0000 the same
	 * way...
	 */
	if (propInfo[numItems] != '\0') {
	    propData = ckalloc((size_t) numItems + 1);
	    strcpy(propData, propInfo);
	    propData[numItems] = '\0';
	}
        interp = retrPtr->interp;
        Tcl_Preserve((ClientData) interp);
	result = (*retrPtr->proc)(retrPtr->clientData, interp, propData);
	Tcl_Release((ClientData) interp);
	if (propData != propInfo) {
	    ckfree((char *) propData);
	}
	if (result != TCL_OK) {
	    retrPtr->result = result;
	}
    } else if (numItems == 0) {
	retrPtr->result = TCL_OK;
    } else {
	char *string;

	if (format != 32) {
	    char buf[64 + TCL_INTEGER_SPACE];

	    sprintf(buf,
		    "bad format for selection: wanted \"32\", got \"%d\"",
		    format);
	    Tcl_SetResult(retrPtr->interp, buf, TCL_VOLATILE);
	    retrPtr->result = TCL_ERROR;
	    goto done;
	}
	string = SelCvtFromX((long *) propInfo, (int) numItems, type,
		(Tk_Window) retrPtr->winPtr);
        interp = retrPtr->interp;
        Tcl_Preserve((ClientData) interp);
	result = (*retrPtr->proc)(retrPtr->clientData, interp, string);
        Tcl_Release((ClientData) interp);
	if (result != TCL_OK) {
	    retrPtr->result = result;
	}
	ckfree(string);
    }

    done:
    XFree(propInfo);
    retrPtr->idleTime = 0;
}

/*
 *----------------------------------------------------------------------
 *
 * SelectionSize --
 *
 *	This procedure is called when the selection is too large to
 *	send in a single buffer;  it computes the total length of
 *	the selection in bytes.
 *
 * Results:
 *	The return value is the number of bytes in the selection
 *	given by selPtr.
 *
 * Side effects:
 *	The selection is retrieved from its current owner (this is
 *	the only way to compute its size).
 *
 *----------------------------------------------------------------------
 */

static int
SelectionSize(selPtr)
    TkSelHandler *selPtr;	/* Information about how to retrieve
				 * the selection whose size is wanted. */
{
    char buffer[TK_SEL_BYTES_AT_ONCE+1];
    int size, chunkSize;
    TkSelInProgress ip;

    size = TK_SEL_BYTES_AT_ONCE;
    ip.selPtr = selPtr;
    ip.nextPtr = TkSelGetInProgress();
    TkSelSetInProgress(&ip);
    do {
	chunkSize = (*selPtr->proc)(selPtr->clientData, size,
			(char *) buffer, TK_SEL_BYTES_AT_ONCE);
	if (ip.selPtr == NULL) {
	    size = 0;
	    break;
	}
	size += chunkSize;
    } while (chunkSize == TK_SEL_BYTES_AT_ONCE);
    TkSelSetInProgress(ip.nextPtr);
    return size;
}

/*
 *----------------------------------------------------------------------
 *
 * IncrTimeoutProc --
 *
 *	This procedure is invoked once a second while sending the
 *	selection to a requestor in INCR mode.  After a while it
 *	gives up and aborts the selection operation.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	A new timeout gets registered so that this procedure gets
 *	called again in another second, unless too many seconds
 *	have elapsed, in which case incrPtr is marked as "all done".
 *
 *----------------------------------------------------------------------
 */

static void
IncrTimeoutProc(clientData)
    ClientData clientData;		/* Information about INCR-mode
					 * selection retrieval for which
					 * we are selection owner. */
{
    register IncrInfo *incrPtr = (IncrInfo *) clientData;

    incrPtr->idleTime++;
    if (incrPtr->idleTime >= 5) {
	incrPtr->numIncrs = 0;
    } else {
	incrPtr->timeout = Tcl_CreateTimerHandler(1000, IncrTimeoutProc,
		(ClientData) incrPtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * SelCvtToX --
 *
 *	Given a selection represented as a string (the normal Tcl form),
 *	convert it to the ICCCM-mandated format for X, depending on
 *	the type argument.  This procedure and SelCvtFromX are inverses.
 *
 * Results:
 *	The return value is a malloc'ed buffer holding a value
 *	equivalent to "string", but formatted as for "type".  It is
 *	the caller's responsibility to free the string when done with
 *	it.  The word at *numLongsPtr is filled in with the number of
 *	32-bit words returned in the result.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static long *
SelCvtToX(string, type, tkwin, numLongsPtr)
    char *string;		/* String representation of selection. */
    Atom type;			/* Atom specifying the X format that is
				 * desired for the selection.  Should not
				 * be XA_STRING (if so, don't bother calling
				 * this procedure at all). */
    Tk_Window tkwin;		/* Window that governs atom conversion. */
    int *numLongsPtr;		/* Number of 32-bit words contained in the
				 * result. */
{
    register char *p;
    char *field;
    int numFields;
    long *propPtr, *longPtr;
#define MAX_ATOM_NAME_LENGTH 100
    char atomName[MAX_ATOM_NAME_LENGTH+1];

    /*
     * The string is assumed to consist of fields separated by spaces.
     * The property gets generated by converting each field to an
     * integer number, in one of two ways:
     * 1. If type is XA_ATOM, convert each field to its corresponding
     *	  atom.
     * 2. If type is anything else, convert each field from an ASCII number
     *    to a 32-bit binary number.
     */

    numFields = 1;
    for (p = string; *p != 0; p++) {
	if (isspace(UCHAR(*p))) {
	    numFields++;
	}
    }
    propPtr = (long *) ckalloc((unsigned) numFields*sizeof(long));

    /*
     * Convert the fields one-by-one.
     */

    for (longPtr = propPtr, *numLongsPtr = 0, p = string;
	    ; longPtr++, (*numLongsPtr)++) {
	while (isspace(UCHAR(*p))) {
	    p++;
	}
	if (*p == 0) {
	    break;
	}
	field = p;
	while ((*p != 0) && !isspace(UCHAR(*p))) {
	    p++;
	}
	if (type == XA_ATOM) {
	    int length;

	    length = p - field;
	    if (length > MAX_ATOM_NAME_LENGTH) {
		length = MAX_ATOM_NAME_LENGTH;
	    }
	    strncpy(atomName, field, (unsigned) length);
	    atomName[length] = 0;
	    *longPtr = (long) Tk_InternAtom(tkwin, atomName);
	} else {
	    char *dummy;

	    *longPtr = strtol(field, &dummy, 0);
	}
    }
    return propPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * SelCvtFromX --
 *
 *	Given an X property value, formatted as a collection of 32-bit
 *	values according to "type" and the ICCCM conventions, convert
 *	the value to a string suitable for manipulation by Tcl.  This
 *	procedure is the inverse of SelCvtToX.
 *
 * Results:
 *	The return value is the string equivalent of "property".  It is
 *	malloc-ed and should be freed by the caller when no longer
 *	needed.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static char *
SelCvtFromX(propPtr, numValues, type, tkwin)
    register long *propPtr;	/* Property value from X. */
    int numValues;		/* Number of 32-bit values in property. */
    Atom type;			/* Type of property  Should not be
				 * XA_STRING (if so, don't bother calling
				 * this procedure at all). */
    Tk_Window tkwin;		/* Window to use for atom conversion. */
{
    char *result;
    int resultSpace, curSize, fieldSize;
    CONST char *atomName;

    /*
     * Convert each long in the property to a string value, which is
     * either the name of an atom (if type is XA_ATOM) or a hexadecimal
     * string.  Make an initial guess about the size of the result, but
     * be prepared to enlarge the result if necessary.
     */

    resultSpace = 12*numValues+1;
    curSize = 0;
    atomName = "";	/* Not needed, but eliminates compiler warning. */
    result = (char *) ckalloc((unsigned) resultSpace);
    *result  = '\0';
    for ( ; numValues > 0; propPtr++, numValues--) {
	if (type == XA_ATOM) {
	    atomName = Tk_GetAtomName(tkwin, (Atom) *propPtr);
	    fieldSize = strlen(atomName) + 1;
	} else {
	    fieldSize = 12;
	}
	if (curSize+fieldSize >= resultSpace) {
	    char *newResult;

	    resultSpace *= 2;
	    if (curSize+fieldSize >= resultSpace) {
		resultSpace = curSize + fieldSize + 1;
	    }
	    newResult = (char *) ckalloc((unsigned) resultSpace);
	    strncpy(newResult, result, (unsigned) curSize);
	    ckfree(result);
	    result = newResult;
	}
	if (curSize != 0) {
	    result[curSize] = ' ';
	    curSize++;
	}
	if (type == XA_ATOM) {
	    strcpy(result+curSize, atomName);
	} else {
	    sprintf(result+curSize, "0x%x", (unsigned int) *propPtr);
	}
	curSize += strlen(result+curSize);
    }
    return result;
}