Window with em-dash in title causes missing focus_changed hook (xconnection.cpp: 347: Can not create text list)

[The-Compiler]

On v0.9.5 (or current git master, 5cc2914), with a reproducer such as:

from PyQt5.QtWidgets import QApplication, QWidget
app = QApplication([])
w = QWidget()
w.setWindowTitle("—x")
w.show()
app.exec()

When focusing the window, no focus_changed hook is shown with hc --idle. After a hc watch clients.focus.title and hc watch clients.focus.winid, the winid one is reported, but the title one is also missing for that window.

Running hlwm with --verbose shows:

../../src/xconnection.cpp: 347: Can not create text list

from here:

herbstluftwm/src/xconnection.cpp

Lines 337 to 349 in 138f65b

	int status = Xutf8TextListToTextProperty(
	m_display, (char**) value_c_str.data(), value_c_str.size(),
	XUTF8StringStyle, &text_prop);
	if (status != Success) {
	// maybe no locale support.
	status = XmbTextListToTextProperty(
	m_display, (char**) value_c_str.data(), value_c_str.size(),
	XStdICCTextStyle, &text_prop);
	}
	if (status != Success) {
	HSDebug("Can not create text list\n");
	return;
	}

I've tried stepping into Xutf8TextListToTextProperty to understand what's going on, but I have no idea what I'm seeing exactly.

The input data looks as it should:

(gdb) p value
$1 = std::vector of length 3, capacity 3 = {"focus_changed", "0x400006", "—x"}
(gdb) p value_c_str
$2 = std::vector of length 3, capacity 3 = {0x55555589f140 "focus_changed", 0x55555589f160 "0x400006", 0x55555589f180 "—x"}

Also note that when using only — (no x), the hook is emitted fine, just without any arguments. Similarly, with things like hc echo "x—x", the dash is just dropped (it echos xx instead).

But when coming from a window title, and being >1 character, it looks like Xutf8TextListToTextProperty returns 1, because the underlying _XTextListToTextProperty gets 1 as unconv_num.

Stack:

#0  _XTextListToTextProperty (lcd=0x555555743180, dpy=0x55555575b260, from_type=from_type@entry=0x7ffff7e19b43 "utf8String", list=0x55555589b7e0 "\220ˋUUU", count=3, style=XUTF8StringStyle, text_prop=0x7fffffffc070) at xlibi18n/lcTxtPr.c:182
#1  0x00007ffff7db535f in _Xutf8TextListToTextProperty (lcd=<optimized out>, dpy=<optimized out>, list=<optimized out>, count=<optimized out>, style=<optimized out>, text_prop=<optimized out>) at xlibi18n/lcTxtPr.c:252
#2  0x00005555556ba337 in XConnection::setPropertyString (this=this@entry=0x555555757920, w=2097155, property=293, value=std::vector of length 3, capacity 3 = {...}) at ../../src/xconnection.cpp:337
#3  0x0000555555613605 in IpcServer::emitHook (this=this@entry=0x55555576f260, args=std::vector of length 3, capacity 3 = {...}) at ../../src/ipc-server.cpp:104
#4  0x00005555556124eb in hook_emit (args=std::vector of length 3, capacity 3 = {...}) at ../../src/hook.cpp:15
#5  0x00005555555b1512 in ClientManager::focusedClientChanges (this=<optimized out>, newFocus=0x555555893be0) at ../../src/clientmanager.cpp:548
#6  0x00005555555b265d in std::__invoke_impl<void, void (ClientManager::*&)(Client*), ClientManager*&, Client*> (__t=<optimized out>, __f=<optimized out>) at /usr/include/c++/12.2.0/bits/invoke.h:74
#7  std::__invoke<void (ClientManager::*&)(Client*), ClientManager*&, Client*> (__fn=<optimized out>) at /usr/include/c++/12.2.0/bits/invoke.h:96
#8  std::_Bind<void (ClientManager::*(ClientManager*, std::_Placeholder<1>))(Client*)>::__call<void, Client*&&, 0ul, 1ul>(std::tuple<Client*&&>&&, std::_Index_tuple<0ul, 1ul>) (__args=..., this=<optimized out>) at /usr/include/c++/12.2.0/functional:484
#9  std::_Bind<void (ClientManager::*(ClientManager*, std::_Placeholder<1>))(Client*)>::operator()<Client*, void>(Client*&&) (this=<optimized out>) at /usr/include/c++/12.2.0/functional:567
#10 std::__invoke_impl<void, std::_Bind<void (ClientManager::*(ClientManager*, std::_Placeholder<1>))(Client*)>&, Client*>(std::__invoke_other, std::_Bind<void (ClientManager::*(ClientManager*, std::_Placeholder<1>))(Client*)>&, Client*&&) (__f=...) at /usr/include/c++/12.2.0/bits/invoke.h:61
#11 std::__invoke_r<void, std::_Bind<void (ClientManager::*(ClientManager*, std::_Placeholder<1>))(Client*)>&, Client*>(std::_Bind<void (ClientManager::*(ClientManager*, std::_Placeholder<1>))(Client*)>&, Client*&&) (__fn=...) at /usr/include/c++/12.2.0/bits/invoke.h:154
#12 std::_Function_handler<void (Client*), std::_Bind<void (ClientManager::*(ClientManager*, std::_Placeholder<1>))(Client*)> >::_M_invoke(std::_Any_data const&, Client*&&) (__functor=..., __args#0=<optimized out>) at /usr/include/c++/12.2.0/bits/std_function.h:290
#13 0x000055555563aace in std::function<void (Client*)>::operator()(Client*) const (__args#0=<optimized out>, this=0x55555586a880) at /usr/include/c++/12.2.0/bits/std_function.h:591
#14 Signal_<Client*>::emit (data=<synthetic pointer>: 0x555555893be0, this=<optimized out>) at ../../src/signal.h:68
#15 Link_<Client>::operator= (new_value=0x555555893be0, this=<optimized out>) at ../../src/link.h:30
#16 Monitor::applyLayout (this=0x555555893250) at ../../src/monitor.cpp:275
#17 0x0000555555641c9c in MonitorManager::lock_number_changed (this=<optimized out>) at ../../src/monitormanager.cpp:494
#18 0x0000555555673eb4 in operator() (__closure=<optimized out>) at ../../src/settings.cpp:440
#19 std::__invoke_impl<void, Settings::injectDependencies(Root*)::<lambda(bool)>&, long unsigned int> (__f=...) at /usr/include/c++/12.2.0/bits/invoke.h:61
#20 std::__invoke_r<void, Settings::injectDependencies(Root*)::<lambda(bool)>&, long unsigned int> (__fn=...) at /usr/include/c++/12.2.0/bits/invoke.h:154
#21 std::_Function_handler<void(long unsigned int), Settings::injectDependencies(Root*)::<lambda(bool)> >::_M_invoke(const std::_Any_data &, unsigned long &&) (__functor=..., __args#0=<optimized out>) at /usr/include/c++/12.2.0/bits/std_function.h:290
#22 0x0000555555641c31 in std::function<void (unsigned long)>::operator()(unsigned long) const (__args#0=<optimized out>, this=0x5555558730e0) at /usr/include/c++/12.2.0/bits/std_function.h:591
#23 Signal_<unsigned long>::emit (data=<optimized out>, this=<optimized out>) at ../../src/signal.h:68
#24 Attribute_<unsigned long>::operator= (payload=<optimized out>, this=<optimized out>) at ../../src/attribute_.h:141
#25 MonitorManager::unlock (this=<optimized out>) at ../../src/monitormanager.cpp:485
#26 0x000055555561b361 in focus_client (client=client@entry=0x555555893be0, switch_tag=switch_tag@entry=false, switch_monitor=switch_monitor@entry=true, raise=<optimized out>) at ../../src/layout.cpp:860
#27 0x00005555556bf4ad in XMainLoop::buttonpress (this=0x7fffffffc770, be=0x7fffffffc530) at ../../src/xmainloop.cpp:294
#28 0x00005555556be9c4 in XMainLoop::run (this=this@entry=0x7fffffffc770) at ../../src/xmainloop.cpp:209
#29 0x000055555557c69e in main (argc=<optimized out>, argv=0x7fffffffcb68) at ../../src/main.cpp:449

The manpage for that function says:

If the supplied text is not fully convertible to the specified encoding, the functions
return the number of unconvertible characters. Each unconvertible character is converted
to an implementation-defined and encoding-specific default string. Otherwise, the
functions return Success. Note that full convertibility to all styles except XStringStyle
is guaranteed.

So maybe the check for Success is actually a bit too strict there? Not sure if there is a more proper solution, though.

[Wasja7]

For anybody who looks for a workaround until this issue is solved: xprop -root -spy "_NET_ACTIVE_WINDOW" does essentially the same as herbstclient -i focus_changed

[The-Compiler]

Probably related: Em dash missing from WM_NAME with libx11-1.8.2 (#167) · Issues · xorg / lib / libX11 · GitLab