[sgt/utils] / xcopy / xcopy.c

/*
 * xcopy: quickly pipe text data into, or out of, the primary X
 * selection
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <math.h>
#include <errno.h>
#include <assert.h>

#include <X11/X.h>
#include <X11/Intrinsic.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xatom.h>

int init_X(void);
void run_X(void);
void done_X(void);
void full_redraw(void);
void do_paste(Window window, Atom property, int Delete);

char *pname;			       /* program name */

void error (char *fmt, ...);

/* set from command-line parameters */
char *display = NULL;
enum { STRING, CTEXT, UTF8, TARGETS, TIMESTAMP, CUSTOM } mode = STRING;
int use_clipboard = False;
char *custom_seltype = NULL;
int fork_when_writing = True;
int use_cutbuffers = True;
int use_outgoing_incr = True;
int sel_delta = 16384;

/* selection data */
char *seltext;
int sellen, selsize;

/* incremental transfers still pending when we return to the event loop */
struct incr {
    Window window;
    Atom property;
    Atom type;
    int format;
    unsigned char *data;
    size_t size;
} *incrs = NULL;
int nincrs = 0, incrsize = 0;

/* functional parameters */
int reading;                           /* read instead of writing? */
int convert_to_ctext = True;	       /* Xmb convert to compound text? */
int verbose;

const char usagemsg[] =
    "usage: xcopy [ -r ] [ -u | -c ] [ -C ]\n"
    "modes: -r       read X selection and print on stdout\n"
    "       no -r    write to X selection from stdin\n"
    " read: -t       get the list of targets available to retrieve\n"
    "       -T       get the time stamp of the selection contents\n"
    "       -a atom  get an arbitrary form of the selection data\n"
    "       -v       verbosely report progress in reading selection\n"
    "write: -F       remain in foreground until selection reclaimed\n"
    "       -I       do not attempt incremental transfers (INCR)\n"
    " both: -u       work with UTF8_STRING type selections\n"
    "       -c       work with COMPOUND_TEXT type selections\n"
    "       -C       suppress automatic conversion to COMPOUND_TEXT\n"
    "       -b       use the CLIPBOARD rather than the PRIMARY selection\n"
    "       -d size  transfer data in chunks of at most <size> (default 16384)\n"
    "       -B       do not use root window cut buffers\n"
    " also: xcopy --version              report version number\n"
    "       xcopy --help                 display this help text\n"
    "       xcopy --licence              display the (MIT) licence text\n"
    ;

void usage(void) {
    fputs(usagemsg, stdout);
}

const char licencemsg[] =
    "xcopy is copyright 2001-2004,2008 Simon Tatham.\n"
    "\n"
    "Permission is hereby granted, free of charge, to any person\n"
    "obtaining a copy of this software and associated documentation files\n"
    "(the \"Software\"), to deal in the Software without restriction,\n"
    "including without limitation the rights to use, copy, modify, merge,\n"
    "publish, distribute, sublicense, and/or sell copies of the Software,\n"
    "and to permit persons to whom the Software is furnished to do so,\n"
    "subject to the following conditions:\n"
    "\n"
    "The above copyright notice and this permission notice shall be\n"
    "included in all copies or substantial portions of the Software.\n"
    "\n"
    "THE SOFTWARE IS PROVIDED \"AS IS\", WITHOUT WARRANTY OF ANY KIND,\n"
    "EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF\n"
    "MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND\n"
    "NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS\n"
    "BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN\n"
    "ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN\n"
    "CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE\n"
    "SOFTWARE.\n"
    ;

void licence(void) {
    fputs(licencemsg, stdout);
}

void version(void) {
#define SVN_REV "$Revision$"
    char rev[sizeof(SVN_REV)];
    char *p, *q;

    strcpy(rev, SVN_REV);

    for (p = rev; *p && *p != ':'; p++);
    if (*p) {
        p++;
        while (*p && isspace(*p)) p++;
        for (q = p; *q && *q != '$'; q++);
        if (*q) *q = '\0';
        printf("xcopy revision %s\n", p);
    } else {
        printf("xcopy: unknown version\n");
    }
}

int main(int ac, char **av) {
    int n;
    int eventloop;

    pname = *av;

    /* parse the command line arguments */
    while (--ac > 0) {
	char *p = *++av;

	if (!strcmp(p, "-display") || !strcmp(p, "-disp")) {
	    if (!av[1])
		error ("option `%s' expects a parameter", p);
	    display = *++av, --ac;
        } else if (!strcmp(p, "-r")) {
            reading = True;
        } else if (!strcmp(p, "-u")) {
            mode = UTF8;
        } else if (!strcmp(p, "-c")) {
            mode = CTEXT;
        } else if (!strcmp(p, "-C")) {
            convert_to_ctext = False;
        } else if (!strcmp(p, "-b")) {
            use_clipboard = True;
        } else if (!strcmp(p, "-t")) {
            mode = TARGETS;
        } else if (!strcmp(p, "-T")) {
            mode = TIMESTAMP;
        } else if (!strcmp(p, "-I")) {
            use_outgoing_incr = False;
        } else if (!strcmp(p, "-B")) {
            use_cutbuffers = False;
        } else if (!strcmp(p, "-a")) {
	    if (--ac > 0)
		custom_seltype = *++av;
	    else
		error ("expected an argument to `-a'");
            mode = CUSTOM;
        } else if (!strcmp(p, "-d")) {
	    if (--ac > 0)
		sel_delta = atoi(*++av);
	    else
		error ("expected an argument to `-d'");
	} else if (!strcmp(p, "-F")) {
	    fork_when_writing = False;
	} else if (!strcmp(p, "-v")) {
	    verbose = True;
        } else if (!strcmp(p, "--help")) {
	    usage();
	    return 0;
        } else if (!strcmp(p, "--version")) {
            version();
	    return 0;
        } else if (!strcmp(p, "--licence") || !strcmp(p, "--license")) {
            licence();
	    return 0;
	} else if (*p=='-') {
	    error ("unrecognised option `%s'", p);
	} else {
	    error ("no parameters required");
	}
    }

    if (!reading) {
	if (mode == TARGETS || mode == TIMESTAMP || mode == CUSTOM) {
	    error ("%s not supported in writing mode; use -r",
		   (mode == TARGETS ? "-t" :
		    mode == TIMESTAMP ? "-T" :
		    /* mode == CUSTOM ? */ "-a"));
	}
    }

    if (!reading) {
        seltext = malloc(sel_delta);
        if (!seltext)
            error ("out of memory");
        selsize = sel_delta;
        sellen = 0;
        do {
            n = fread(seltext+sellen, 1, selsize-sellen, stdin);
            sellen += n;
            if (sellen >= selsize) {
                seltext = realloc(seltext, selsize += sel_delta);
                if (!seltext)
                    error ("out of memory");
            }
        } while (n > 0);
        if (sellen == selsize) {
            seltext = realloc(seltext, selsize += sel_delta);
            if (!seltext)
                error ("out of memory");
        }
        seltext[sellen] = '\0';
    }

    eventloop = init_X();
    if (!reading && fork_when_writing) {
        /*
         * If we are writing the selection, we must go into the
         * background now.
         */
        int pid = fork();
        if (pid < 0) {
            error("unable to fork: %s", strerror(errno));
        } else if (pid > 0) {
            /*
             * we are the parent; just exit
             */
            return 0;
        }
        /*
         * we are the child
         */
        close(0);
        close(1);
        close(2);
        chdir("/");
    }
    if (eventloop)
        run_X();
    done_X();
    return 0;
}

/* handle errors */

void error (char *fmt, ...) {
    va_list ap;
    char errbuf[200];

    done_X();
    va_start (ap, fmt);
    vsprintf (errbuf, fmt, ap);
    va_end (ap);
    fprintf (stderr, "%s: %s\n", pname, errbuf);
    exit (1);
}

/* begin the X interface */

char *lcasename = "xcopy";
char *ucasename = "XCopy";

Display *disp = NULL;
Window ourwin = None;
Atom compound_text_atom, targets_atom, timestamp_atom, atom_atom, integer_atom;
Atom multiple_atom, atom_pair_atom, incr_atom;
int screen, wwidth, wheight;

Atom strtype = XA_STRING;
Atom sel_atom = XA_PRIMARY;
Atom expected_type = (Atom)None;
int expected_format = 8;

static const char *translate_atom(Display *disp, Atom atom)
{
    if (atom == None)
	return "None";
    else
	return XGetAtomName(disp, atom);
}

/*
 * Returns TRUE if we need to enter an event loop, FALSE otherwise.
 */
int init_X(void) {
    Window root;
    int x = 0, y = 0, width = 512, height = 128;
    int i, got = 0;
    XWMHints wm_hints;
    XSizeHints size_hints;
    XClassHint class_hints;
    XTextProperty textprop;
    XGCValues gcv;

    /* open the X display */
    disp = XOpenDisplay (display);
    if (!disp)
	error ("unable to open display");

    targets_atom = XInternAtom(disp, "TARGETS", False);
    timestamp_atom = XInternAtom(disp, "TIMESTAMP", False);
    atom_atom = XInternAtom(disp, "ATOM", False);
    atom_pair_atom = XInternAtom(disp, "ATOM_PAIR", False);
    multiple_atom = XInternAtom(disp, "MULTIPLE", False);
    integer_atom = XInternAtom(disp, "INTEGER", False);
    incr_atom = XInternAtom(disp, "INCR", False);
    if (mode == UTF8) {
	strtype = XInternAtom(disp, "UTF8_STRING", False);
    } else if (mode == CTEXT) {
	strtype = XInternAtom(disp, "COMPOUND_TEXT", False);
    } else if (mode == TARGETS) {
	strtype = targets_atom;
	expected_type = atom_atom;
	expected_format = 32;
    } else if (mode == TIMESTAMP) {
	strtype = timestamp_atom;
	expected_type = integer_atom;
	expected_format = 32;
    } else if (mode == CUSTOM) {
	strtype = XInternAtom(disp, custom_seltype, True);
	if (!strtype)
	    error ("atom '%s' does not exist on the server", custom_seltype);
	expected_format = 0;
    }
    if (use_clipboard) {
        sel_atom = XInternAtom(disp, "CLIPBOARD", False);
    }

    /* get the screen and root-window */
    screen = DefaultScreen (disp);
    root = RootWindow (disp, screen);

    x = y = 0;
    width = height = 10;	       /* doesn't really matter */

    /* actually create the window */
    ourwin = XCreateSimpleWindow (disp, root, x, y, width, height,0, 
				  BlackPixel(disp, screen),
				  WhitePixel(disp, screen));

    /* resource class name */
    class_hints.res_name = lcasename;
    class_hints.res_class = ucasename;
    XSetClassHint (disp, ourwin, &class_hints);

    /* do selection fiddling */
    if (reading) {
        /*
         * We are reading the selection. Call XConvertSelection to
         * request transmission of the selection data in the
         * appropriate format; the X event loop will then wait to
         * receive the data from the selection owner. Also we need to
         * make sure we receive PropertyNotify events, for INCR
         * transfers.
	 *
	 * If there is no selection owner, look in the cut buffer
	 * property on the root window.
         */
        XSelectInput(disp, ourwin, PropertyChangeMask);
        if (XGetSelectionOwner(disp, sel_atom) != None) {
            Atom sel_property = XInternAtom(disp, "VT_SELECTION", False);
	    if (verbose)
		fprintf(stderr, "calling XConvertSelection: selection=%s"
			" target=%s property=%s requestor=%08lx\n",
			translate_atom(disp, sel_atom),
			translate_atom(disp, strtype),
			translate_atom(disp, sel_property),
			ourwin);
            XConvertSelection(disp, sel_atom, strtype,
                              sel_property, ourwin, CurrentTime);
            return True;
        } else if (use_cutbuffers) {
            /* No primary selection, so use the cut buffer. */
	    if (verbose)
		fprintf(stderr, "no selection owner: trying cut buffer\n");
            if (strtype == XA_STRING)
		do_paste(DefaultRootWindow(disp), XA_CUT_BUFFER0, True);
            return False;
        } else {
            /* Last fallback: do nothing. */
            return False;
        }
    } else {
        /*
         * We are writing to the selection, so we establish ourselves
         * as selection owner.
         *
         * Also place the data in CUT_BUFFER0, if it isn't of an
         * exotic type (cut buffers can only take ordinary string
         * data, it turns out) or bigger than our maximum chunk size.
         */
        XSetSelectionOwner (disp, sel_atom, ourwin, CurrentTime);
        if (XGetSelectionOwner (disp, sel_atom) != ourwin)
            error ("unable to obtain primary X selection");
        compound_text_atom = XInternAtom(disp, "COMPOUND_TEXT", False);
	if (strtype == XA_STRING && sellen <= sel_delta && use_cutbuffers) {
	    /*
	     * ICCCM-required cut buffer initialisation.
	     */
	    XChangeProperty(disp, root, XA_CUT_BUFFER0,
			    XA_STRING, 8, PropModeAppend, "", 0);
	    XChangeProperty(disp, root, XA_CUT_BUFFER1,
			    XA_STRING, 8, PropModeAppend, "", 0);
	    XChangeProperty(disp, root, XA_CUT_BUFFER2,
			    XA_STRING, 8, PropModeAppend, "", 0);
	    XChangeProperty(disp, root, XA_CUT_BUFFER3,
			    XA_STRING, 8, PropModeAppend, "", 0);
	    XChangeProperty(disp, root, XA_CUT_BUFFER4,
			    XA_STRING, 8, PropModeAppend, "", 0);
	    XChangeProperty(disp, root, XA_CUT_BUFFER5,
			    XA_STRING, 8, PropModeAppend, "", 0);
	    XChangeProperty(disp, root, XA_CUT_BUFFER6,
			    XA_STRING, 8, PropModeAppend, "", 0);
	    XChangeProperty(disp, root, XA_CUT_BUFFER7,
			    XA_STRING, 8, PropModeAppend, "", 0);
	    /*
	     * Rotate the cut buffers and add our text in CUT_BUFFER0.
	     */
	    XRotateBuffers(disp, 1);
	    XStoreBytes(disp, seltext, sellen);
	}
        return True;
    }
}

void write_data(Window requestor, Atom property, Atom type, int format,
                void *vdata, size_t size)
{
    int bformat = format / 8;          /* bytes per element */
    unsigned char *data = (unsigned char *)vdata;
    XEvent ev;

    if (!use_outgoing_incr || size * bformat <= sel_delta) {
	XChangeProperty(disp, requestor, property, type, format,
                        PropModeReplace, data, size);
    } else {
        /*
         * For large data, an incremental transfer as per ICCCM 2.7.2.
         */
        Cardinal totalsize = size * bformat;
        Cardinal sent, thissize;

        /*
         * We're going to need PropertyNotify events on the target
         * window to tell us when to send the next chunk.
         */
        XSelectInput(disp, requestor, PropertyChangeMask);

        /*
         * Start by sending a single 32-bit word with type INCR giving
         * the total size in bytes.
         */
	XChangeProperty(disp, requestor, property, incr_atom, 32,
                        PropModeReplace, (unsigned char *)&totalsize, 1);

        /*
         * Now set up an entry in our list of ongoing incremental
         * transfers, so that whenever that property is deleted, we'll
         * send the next batch.
         */
        if (nincrs >= incrsize) {
            incrsize = nincrs * 9 / 8 + 16;
            incrs = realloc(incrs, incrsize * sizeof(*incrs));
            if (!incrs)
                error ("out of memory");
        }
        incrs[nincrs].window = requestor;
        incrs[nincrs].property = property;
        incrs[nincrs].type = type;
        incrs[nincrs].format = format;
        incrs[nincrs].size = totalsize;
        incrs[nincrs].data = malloc(totalsize);
        if (!incrs[nincrs].data)
            error("out of memory");
        memcpy(incrs[nincrs].data, data, size);
        nincrs++;
    }
}

Atom convert_sel_inner(Window requestor, Atom target, Atom property) {
    if (target == strtype) {
	write_data(requestor, property, strtype, 8, seltext, sellen);
	return property;
    } else if (target == compound_text_atom && convert_to_ctext) {
	XTextProperty tp;
	XmbTextListToTextProperty(disp, &seltext, 1, XCompoundTextStyle, &tp);
	write_data(requestor, property, target, tp.format, tp.value,tp.nitems);
	return property;
    } else if (target == targets_atom) {
	Atom targets[16];
	int len = 0;
	targets[len++] = timestamp_atom;
	targets[len++] = targets_atom;
	targets[len++] = multiple_atom;
	targets[len++] = strtype;
	if (strtype != compound_text_atom && convert_to_ctext)
	    targets[len++] = compound_text_atom;
	write_data(requestor, property, atom_atom, 32, targets, len);
	return property;
    } else if (target == timestamp_atom) {
	Time rettime = CurrentTime;
	write_data(requestor, property, integer_atom, 32, &rettime, 1);
	return property;
    } else {
	return None;
    }
}

Atom convert_sel_outer(Window requestor, Atom target, Atom property) {
    if (target == multiple_atom) {
	/*
	 * Support for the MULTIPLE selection type, since it's
	 * specified as required in the ICCCM. Completely
	 * untested, though, because I have no idea of what X
	 * application might implement it for me to test against.
	 */

	int size = sel_delta;
	Atom actual_type;
	int actual_format, i;
	long nitems, bytes_after, nread;
	unsigned char *data;
	Atom *adata;

        if (property == (Atom)None)
            return None;               /* ICCCM says this isn't allowed */

	/*
	 * Fetch the requestor's window property giving a list of
	 * selection requests.
	 */
	while (XGetWindowProperty(disp, requestor, property, 0, size,
				  False, AnyPropertyType, &actual_type,
				  &actual_format, &nitems, &bytes_after,
				  (unsigned char **) &data) == Success &&
	       nitems * (actual_format / 8) == size) {
	    XFree(data);
	    size *= 3 / 2;
	}

	if (actual_type != atom_pair_atom || actual_format != 32) {
	    XFree(data);
	    return None;
	}

	adata = (Atom *)data;

	for (i = 0; i+1 < nitems; i += 2) {
            if (adata[i+1] != (Atom)None)   /* ICCCM says this isn't allowed */
                adata[i+1] = convert_sel_inner(requestor, adata[i],
                                               adata[i+1]);
	}

	XChangeProperty (disp, requestor, property,
			 atom_pair_atom, 32, PropModeReplace,
			 data, nitems);

	XFree(data);

	return property;
    } else {
        if (property == (Atom)None)
            property = target;      /* ICCCM says this is a sensible default */
	return convert_sel_inner(requestor, target, property);
    }
}

void run_X(void) {
    XEvent ev, e2;
    int i, j;

    while (1) {
	XNextEvent (disp, &ev);
        if (reading) {
            switch (ev.type) {
              case SelectionNotify:
		if (verbose)
		    fprintf(stderr, "got SelectionNotify: requestor=%08lx "
			    "selection=%s target=%s property=%s\n",
			    ev.xselection.requestor,
			    translate_atom(disp, ev.xselection.selection),
			    translate_atom(disp, ev.xselection.target),
			    translate_atom(disp, ev.xselection.property));

                if (ev.xselection.property != None)
                    do_paste(ev.xselection.requestor,
                             ev.xselection.property, False);
                return;
            }
        } else {
            switch (ev.type) {
              case SelectionClear:
                /* Selection has been cleared by another app. */
                return;
              case SelectionRequest:
                e2.xselection.type = SelectionNotify;
                e2.xselection.requestor = ev.xselectionrequest.requestor;
                e2.xselection.selection = ev.xselectionrequest.selection;
                e2.xselection.target = ev.xselectionrequest.target;
                e2.xselection.time = ev.xselectionrequest.time;
                e2.xselection.property =
		    convert_sel_outer(ev.xselectionrequest.requestor,
				      ev.xselectionrequest.target,
				      ev.xselectionrequest.property);
                XSendEvent (disp, ev.xselectionrequest.requestor,
			    False, 0, &e2);
                break;
              case PropertyNotify:
                for (i = j = 0; i < nincrs; i++) {
                    int keep = True;
                    if (incrs[i].window == ev.xproperty.window &&
                        incrs[i].property == ev.xproperty.atom &&
                        ev.xproperty.state == PropertyDelete) {
                        size_t thissize = incrs[i].size;
                        if (thissize > sel_delta)
                            thissize = sel_delta;

                        XChangeProperty(disp,
                                        incrs[i].window, incrs[i].property,
                                        incrs[i].type, incrs[i].format,
                                        PropModeReplace, incrs[i].data,
                                        thissize / (incrs[i].format/8));

                        if (thissize == 0) {
                            /*
                             * If we've just sent a zero-length block,
                             * the incremental transfer is over and we
                             * should delete this entry.
                             */
                            keep = False;
                        }

                        incrs[i].data += thissize;
                        incrs[i].size -= thissize;
                    }
                    if (keep) {
                        if (j != i)
                            incrs[j] = incrs[i];
                        j++;
                    }
                }
                nincrs = j;
                break;
            }
        }
    }
}

void done_X(void) {
    int i;

    if (ourwin != None)
	XDestroyWindow (disp, ourwin);
    if (disp)
	XCloseDisplay (disp);
}

void do_paste(Window window, Atom property, int cutbuffer) {
    Atom actual_type;
    int actual_format, i;
    long nitems, bytes_after, nread;
    unsigned char *data;
    int incremental = False;
    XEvent ev;

    nread = 0;
    while (XGetWindowProperty(disp, window, property, nread / 4, sel_delta / 4,
                              !cutbuffer, AnyPropertyType, &actual_type,
                              &actual_format, &nitems, &bytes_after,
                              (unsigned char **) &data) == Success) {
	if (verbose)
	    fprintf(stderr, "got %ld items of %d-byte data, type=%s;"
		    " %ld to go\n", nitems, actual_format,
		    translate_atom(disp, actual_type), bytes_after);

        /*
         * ICCCM 2.7.2: if we receive data with the type atom set to
         * INCR, it indicates that the actual data will arrive in
         * multiple chunks, terminating with a zero-length one.
         * Between each pair, we must wait for a PropertyNotify event
         * which tells us that the next chunk has arrived.
         */
        if (actual_type == incr_atom && !cutbuffer) {
            incremental = True;
            /*
             * Immediately wait for the first chunk of real data.
             */
            do {
                XMaskEvent(disp, PropertyChangeMask, &ev);
            } while (ev.xproperty.state != PropertyNewValue);
            /*
             * And loop straight back round to read it.
             */
            continue;
        }

	if (nitems > 0) {
	    /*
	     * We expect all returned chunks of data to be
	     * multiples of 4 bytes (because we can only request
	     * the subsequent starting offset in 4-byte
	     * increments). Of course you can store an odd number
	     * of bytes in a selection, so this can't be the case
	     * every time XGetWindowProperty returns; but it
	     * should be the case every time it returns _and there
	     * is more data to come_.
	     *
	     * Hence, whenever XGetWindowProperty returns, we
	     * verify that the size of the data returned _last_
	     * time was divisible by 4.
	     */
	    if ((nread & 3) != 0) {
		error("unexpected data size: %d read (not a multiple"
		      " of 4), but more to come", nread);
	    }

	    if (expected_type != (Atom)None && actual_type != expected_type) {
		const char *expout = translate_atom(disp, expected_type);
		const char *gotout = translate_atom(disp, actual_type);
		error("unexpected data type: expected %s, got %s",
		      expout, gotout);
	    }
	    if (expected_format && expected_format != actual_format) {
		error("unexpected data format: expected %d-bit, got %d-bit",
		      expected_format, actual_format);
	    }
	}

        if (nitems > 0) {
	    if (mode == TARGETS) {
		assert(actual_format == 32);
		int i;
		for (i = 0; i < nitems; i++) {
		    Atom x = ((Atom *)data)[i];
		    printf("%s\n", translate_atom(disp, x));
		}
	    } else if (mode == TIMESTAMP) {
		assert(actual_format == 32);
		Time x = ((Time *)data)[0];
		printf("%lu\n", (unsigned long)x);
	    } else {
		fwrite(data, actual_format / 8, nitems, stdout);
		nread += nitems * actual_format / 8;
	    }
        }
        XFree(data);
	if (bytes_after == 0) {
            /*
             * We've come to the end of the property we're reading.
             */
            if (incremental) {
                /*
                 * For an incremental transfer, this means we wait for
                 * another property to be dumped in the same place on
                 * our window, and loop round again reading that. The
                 * exception is if the total length of the property we
                 * got was zero, which signals the end.
                 */
                if (nread == 0 && nitems == 0)
                    break;             /* all done */

                /* otherwise wait for the next chunk */
                do {
                    XMaskEvent(disp, PropertyChangeMask, &ev);
                } while (ev.xproperty.state != PropertyNewValue);

                /* which we read from the beginning */
                nread = 0;
            } else {
		break;
            }
	}
    }
}