gjw@SPURR.WR.USGS.GOV (Gregory J. Woodhouse) (11/21/90)
Hi, I've got another (presumably) naive question for you. I use the following
routine to read the window ID of the main window of another process from a
property. My purpose in doing so is so that I can use XSendEvent. The
problem is that XInternAtom returns None, even though the slave process
should have created the property already. Here's the code:
/*============================================================================*
* fetch_win *
*============================================================================*/
Bool fetch_win(display, sl_winp)
Display *display;
Window *sl_winp; /* RETURN */
{ /* fetch slave window ID from display manager */
int status;
Window rootwindow;
Atom slwin_atom;
/* These pointers are used for return values from XGetWindowProperty */
int *actual_format;
Atom *actual_type;
unsigned long *nitems;
unsigned long *bytes_after;
unsigned char **data;
rootwindow = RootWindow(display, DefaultScreen(display));
slwin_atom = XInternAtom(display, PROP_NAME, True);
/* only if exists -- this end reads the property */
if (slwin_atom == (Atom) None) {
perror("master: XInternAtom");
return(False);
} else
status = XGetWindowProperty(display, rootwindow, slwin_atom, 0L,
1L, False, XA_WINDOW, actual_type, actual_format,
nitems, bytes_after, data);
if (*actual_format != 32 || *actual_type != XA_WINDOW || *nitems != 1L) {
perror("master: property format");
return(False);
}
if (status != Success) {
(void) fprintf(stderr, "%s: XGetWindowProperty failed", progname);
return(False);
}
/* All went well. */
sl_winp = (Window *) data[0];
return(True);
}gjw@ANDREAS.WR.USGS.GOV (Gregory J. Woodhouse) (11/21/90)
Never mind...it has nothing to do with the code. (Well, I forgot to check report.xproperty.atom) rather, I started my master and slave processes in the wrong order, so the correct PropertyNotify nevcer came. Sorry to bother you all. ----------------------------------------------------------------------------- Gregory Woodhouse |We know that the center of the earth gjw@andreas.wr.usgs.gov |is a fiery molten mass...but it's not (415) 329-4694 (office) |good to dwell on it. (415) 325-7802 (home) | U.S. Geological Survey / 345 Middlefield Rd. MS 977 / Menlo Park, CA 94025 -----------------------------------------------------------------------------
etaylor@wilkins.iaims.bcm.tmc.edu (Eric Taylor) (11/22/90)
You are doing this : int *actual_format ; int *actual_type ; XGetWindowProperty(...,actual_format,actual_type, ...) when you should be doing this : int actual_format ; int actual_type ; XGetWindowProperty(...,&actual_format,&actual_type,...) -- Eric Taylor Baylor College of Medicine etaylor@wilkins.bmc.tmc.edu (713) 798-3776
etaylor@wilkins.iaims.bcm.tmc.edu (Eric Taylor) (11/22/90)
The code fragment you posted WILL abort randomly. You gave XGetWindowProperty serveral uninitialized pointers. "actual_type" and "actual_format" were not the only ones. "nitems", "data", "bytes_after", "actual_type". Your program might work sometimes when the pointers actually pointed to something in your memory. -- Eric Taylor Baylor College of Medicine etaylor@wilkins.bmc.tmc.edu (713) 798-3776
tuceryan@mohawk.cps.msu.edu (Mihran Tuceryan) (01/21/91)
The following is supposed to be a simple test program that draws a straight
line in a window. The window appears but nothing is drawn. What is wrong with
this program? Any help is appreciated. (the display is 8 bits deep and
this is using Xw widgets).
Mihran Tuceryan
email: tuceryan@cps.msu.edu
/*************************************************
* xy.c: Draw a line from (x1,y1) to (x2,y2).
*************************************************/
#include <X11/Intrinsic.h>
#include <X11/StringDefs.h>
#include <Xw/Xw.h>
#include <Xw/WorkSpace.h>
main(argc, argv)
int argc;
char *argv[];
{
int x1, y1, x2, y2;
Widget toplevel, canvas;
GC gc;
XGCValues gcv;
Display *dpy;
Window win;
Arg args[10];
int n = 0;
/* Initialize the Intrinsincs */
toplevel = XtInitialize (argv[0], "SATCS", NULL, 0,
&argc, argv);
dpy = XtDisplay(toplevel);
/* Create the workspace widget. */
canvas = XtCreateManagedWidget ("canvas",
XwworkSpaceWidgetClass,
toplevel, NULL, 0);
/* Alter widget size (p 23) */
n = 0;
XtSetArg (args[n], XtNwidth, 400); n++;
XtSetArg (args[n], XtNheight, 400); n++;
XtSetArg (args[n], XtNforeground, WhitePixel(dpy, DefaultScreen(dpy))); n++;
XtSetArg (args[n], XtNbackground, BlackPixel(dpy, DefaultScreen(dpy))); n++;
XtSetValues (canvas, args, n);
/* Realize the widgets */
XtRealizeWidget (toplevel);
win = XtWindow(canvas);
gcv.background = BlackPixel(dpy, DefaultScreen(dpy));
gcv.foreground = WhitePixel(dpy, DefaultScreen(dpy));
gcv.line_style = LineSolid;
gcv.function = GXcopy;
gc = XtGetGC(canvas,
GCFunction |
GCForeground | GCBackground |
GCLineStyle,
&gcv);
x1 = 50; y1 = 50;
x2 = 100; y2 = 100;
XDrawLine(dpy, win, gc, x1, y1, x2, y2);
XtMainLoop ();
}etaylor@wilkins.iaims.bcm.tmc.edu (Eric Taylor) (01/22/91)
Technically, you can not draw to a window until you have received an Expose Event or something along those lines. -- Eric Taylor Baylor College of Medicine etaylor@wilkins.bcm.tmc.edu (713) 798-3776
stuart_rose@canrem.uucp (stuart rose) (01/23/91)
Mihran Tuceryan writes to All (in the U-WNDWX Conf.) ... In article <1991Jan20.215551.15000@msuinfo.cl.msu.edu> MIHRAN TUCERYAN writes: Try flushing the display buffer before calling the main loop intrinsic. MT> XDrawLine(dpy, win, gc, x1, y1, x2, y2); XFlush(dpy); MT> XtMainLoop (); MT> } Take Care, | stuart.rose@canremote.uucp Stuart | Mississauga, Ontario, Canada. --- ~ DeLuxe}ac #2428 ~ Just a stone's throw from Mississauga City Hall -- Canada Remote Systems. Toronto, Ontario NorthAmeriNet Host
dce@smsc.sony.com (David Elliott) (01/26/91)
In article <1991Jan23.1189.8676@canrem.uucp>, stuart_rose@canrem.uucp (stuart rose) writes: |> Mihran Tuceryan writes to All (in the U-WNDWX Conf.) ... |> In article <1991Jan20.215551.15000@msuinfo.cl.msu.edu> |> MIHRAN TUCERYAN writes: |> |> Try flushing the display buffer before calling the main loop |> intrinsic. |> |> MT> XDrawLine(dpy, win, gc, x1, y1, x2, y2); |> XFlush(dpy); |> MT> XtMainLoop (); |> MT> } Please don't post answers you haven't researched. Flushing won't do anything if the window hasn't already been displayed, such as may be the case if it was started under a window manager that lets the user do the placement (such as twm without RandomPlacement set). Drawing to a window before Expose events have been sent is never guaranteed to work, no matter whether you flush the display buffer or not (in fact, there can even be implementations of Xlib that don't even have a display buffer). -- ...David Elliott ...dce@smsc.sony.com | ...!{uunet,mips}!sonyusa!dce ...(408)944-4073 ..."His lower lip waved poutily with defiance..."