On Thu, 28 Aug 2008, Prof Brian Ripley wrote:
> This is an Xt error, whereas the first one is an Xlib error. It is easy
> to trap it.
>
> You do realize that this will never work? In the current setup all open
> X11 devices must be on the same display, and 'display' is ignored if a
> device is already open. (I don't know if that is documented: I did not
> write the Xlib device nor the help page.)
I have a different problem with the x11() bringing
down R when $DISPLAY does not refer to a valid X
server. I typically sit at a Windows laptop running
a Cygwin X server and use the ssh client/terminal
emulator program 'putty' to run a shell on on Linux,
where I run R. Putty tunnels X protocol and sets
DISPLAY (to something like localhost:11.0) whether or
not the PC's X server is running. If I have forgotten
to start the PC's X server R currently shuts down when
I try to start x11() or the tcl/tk stuff that
available.packages() runs. E.g.,
> x11()
X connection to localhost:11.0 broken (explicit kill or server shutdown).
linuxPrompt%
If I call the XIOErrorHandler(R_X11IOErr) before calling XOpenDisplay()
(in src/modules/X11/devX11.c) then I can trap that error
and have x11() throw an ordinary R error:
> x11()
Error in x11() : X11 I/O error while opening device "localhost:11.0"
>
The following patch sets the IOErrorHandler before XOpenDisplay
and changes the handler a bit so it doesn't assume that some
global variables have been set yet.
It doesn't help the problem in available.packages(). That must
make its own unprotected call to XOpenDisplay().
Index: src/modules/X11/devX11.c
===================================================================
--- src/modules/X11/devX11.c (revision 46454)
+++ src/modules/X11/devX11.c (working copy)
@@ -1080,19 +1080,30 @@
static int R_X11IOErr(Display *dsp)
{
- int fd = ConnectionNumber(display);
- /*
- while (nfonts--) R_XFreeFont(display, fontcache[nfonts].font);
- nfonts = 0;
- */
- removeInputHandler(&R_InputHandlers,
- getInputHandler(R_InputHandlers,fd));
- /*
- XCloseDisplay(display);
- displayOpen = FALSE;
- strcpy(dspname, "");
- */
- error(_("X11 fatal IO error: please save work and shut down R"));
+ int fd ;
+ /* display is only set after successful call to XOpenDisplay.
+ * If it is non-null I think it should be the same as dsp, but
+ * display==NULL & dsp!=NULL means that we have run into a problem
+ * while executing XOpenDisplay.
+ */
+ if (display && displayOpen) {
+ fd = ConnectionNumber(display);
+ /*
+ while (nfonts--) R_XFreeFont(display, fontcache[nfonts].font);
+ nfonts = 0;
+ */
+ removeInputHandler(&R_InputHandlers,
+ getInputHandler(R_InputHandlers,fd));
+ /*
+ XCloseDisplay(display);
+ displayOpen = FALSE;
+ strcpy(dspname, "");
+ */
+ error(_("X11 fatal IO error: please save work and shut down R"));
+ } else if (dsp) { /* In XOpenDisplay() is the intent */
+ char *devname = XDisplayName(dspname) ;
+ error(_("X11 I/O error while opening device \"%s\""), devname);
+ }
return 0; /* but should never get here */
}
@@ -1247,15 +1258,21 @@
/* initialize the X11 device driver data structures. */
if (!displayOpen) {
+ /* Set IOErrorHandler before trying to open the display
+ * just in case DISPLAY is putty tunnelling X11 protocol
+ * to a machine that is not runing an X server. Set dspname
+ * now so R_X11IOErr can show it to user. */
+ XSetIOErrorHandler(R_X11IOErr);
+ strncpy(dspname, p, 101);
+ dspname[100] = '\0';
if ((display = XOpenDisplay(p)) == NULL) {
+ dspname[0] = '\0' ;
warning(_("unable to open connection to X11 display '%s'"), p);
return FALSE;
}
DisplayOpened = TRUE;
Rf_setX11Display(display, gamma_fac, colormodel, maxcube, TRUE);
displayOpen = TRUE;
- strncpy(dspname, p, 101);
- dspname[100] = '\0';
if(xd->handleOwnEvents == FALSE)
addInputHandler(R_InputHandlers, ConnectionNumber(display),
R_ProcessX11Events, XActivity);
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