[patch] fix for BadAtom in X_ChangeProperty when pasting to some client

[Marcin Cieslak]

Hello,

When testing syncterm (http://syncterm.bbsdev.net/) I noticed
that syncterm crashes and (after some fixes) causes crash
in rxvt and the following warning in rxvt-unicode when
pasting some text from rxvt-unicode to syncterm:

X Error occurred, trying to continue after report.
urxvt: X Error of failed request:  BadAtom (invalid Atom parameter)
urxvt: Major opcode of failed request:  18
urxvt: (which is X_ChangeProperty)
urxvt: Atom id in failed request:  0x0
urxvt: Serial number of failed request:  657

The same thing works fine with xterm. This is because
this client sends None property with ConvertRequest. 
This is discouradged by ICCCM but nethertheless I think
it should not cause any problems with the terminal
emulator.

Here are some more sample programs that work the
same way:

http://michael.toren.net/mirrors/doc/X-copy+paste.txt

Below is a patch to rxvt-unicode-9.10 (it applies
also to the CVS trunk):

------------8<----------------------
--- src/screen.C.orig	2011-04-19 23:53:53.000000000 +0200
+++ src/screen.C	2011-04-19 23:57:02.000000000 +0200
@@ -3619,6 +3619,7 @@
 rxvt_term::selection_send (const XSelectionRequestEvent &rq) NOTHROW
 {
   XSelectionEvent ev;
+  Atom property;
 
   ev.type = SelectionNotify;
   ev.property = None;
@@ -3628,6 +3629,16 @@
   ev.target = rq.target;
   ev.time = rq.time;
 
+  /* ICCCM: 2.2. Responsibilities of the Selection Owner   
+   * SelectionRequest:
+   * If the specified property is None , the requestor
+   * an obsolete client. Owners are encouraged
+   * to support these clients by using the specified
+   * target atom as the property name to be used for
+   * the reply.
+   */
+  property = (rq.property == 0) ? rq.target : rq.property;
+
   if (rq.target == xa[XA_TARGETS])
     {
       Atom target_list[6];
@@ -3642,10 +3653,10 @@
       *target++ = xa[XA_UTF8_STRING];
 #endif
 
-      XChangeProperty (dpy, rq.requestor, rq.property, XA_ATOM,
+      XChangeProperty (dpy, rq.requestor, property, XA_ATOM,
                        32, PropModeReplace,
                        (unsigned char *)target_list, target - target_list);
-      ev.property = rq.property;
+      ev.property = property;
     }
 #if TODO // TODO
   else if (rq.target == xa[XA_MULTIPLE])
@@ -3655,15 +3666,15 @@
 #endif
   else if (rq.target == xa[XA_TIMESTAMP] && rq.selection == XA_PRIMARY && selection.text)
     {
-      XChangeProperty (dpy, rq.requestor, rq.property, rq.target,
+      XChangeProperty (dpy, rq.requestor, property, rq.target,
                        32, PropModeReplace, (unsigned char *)&selection_time, 1);
-      ev.property = rq.property;
+      ev.property = property;
     }
   else if (rq.target == xa[XA_TIMESTAMP] && rq.selection == xa[XA_CLIPBOARD] && selection.clip_text)
     {
-      XChangeProperty (dpy, rq.requestor, rq.property, rq.target,
+      XChangeProperty (dpy, rq.requestor, property, rq.target,
                        32, PropModeReplace, (unsigned char *)&clipboard_time, 1);
-      ev.property = rq.property;
+      ev.property = property;
     }
   else if (rq.target == XA_STRING
            || rq.target == xa[XA_TEXT]
@@ -3744,10 +3755,10 @@
           ct.encoding = target;
         }
 
-      XChangeProperty (dpy, rq.requestor, rq.property,
+      XChangeProperty (dpy, rq.requestor, property,
                        ct.encoding, 8, PropModeReplace,
                        ct.value, (int)ct.nitems);
-      ev.property = rq.property;
+      ev.property = property;
 
       if (freect)
         XFree (ct.value);

------------8<----------------------

//Marcin