Wayland fix (namely pncconf's sample panel)

[NTULINUX]

Fixes: #4522

[BsAtHome]

What about the other GUIs?
Also, is there an interaction if this would be run in, for example, xvfb? You set the variable unconditionally. Is that the proper way?

[grandixximo]

Good questions.

The other GUIs are already covered: everything launched through the linuxcnc script inherits PYOPENGL_PLATFORM=x11 from scripts/linuxcnc.in:30-34, so Axis, gmoccapy and qtvcp in normal use never hit this. The gap is only tools started outside that script, pncconf being the report here, and all of them reach OpenGL through gremlin, which is GLX-only code anyway (it imports GdkX11 and dlopens libGL directly). So setting the platform in gremlin covers exactly the consumers that can hit the failure, and nowhere else. Qt-based GUIs use Qt's GL stack and are unaffected either way.

It is not actually unconditional: os.environ.setdefault only sets the variable when it is unset, so an explicit user setting or the linuxcnc.in export takes precedence. Under xvfb there is no Wayland session, so PyOpenGL would select the GLX/x11 platform natively; the setdefault merely pins the value it would have picked anyway, so behavior under xvfb is unchanged. The value x11 also matches what linuxcnc.in already exports.

[rene-dev]

if gremlin has been converted to modern opengl, we dont need the dlopen hack anymore, and can use gtkglarea, which might or might not work on wayland. Background: the hack was needed, as gtkglarea cannot provide a legacy opengl context. this was a major pain during the gtk3 conversion.

[alex-pres]

if gremlin has been converted to modern opengl, we dont need the dlopen hack anymore, and can use gtkglarea, which might or might not work on wayland. Background: the hack was needed, as gtkglarea cannot provide a legacy opengl context. this was a major pain during the gtk3 conversion.

I will check what can be done for this.

[alex-pres]

pncconf and gremlin are confirmed to run on Weston Wayland with #4538 and without this fix.

There are other showstoppers to run on native Wayland [ for example use of GtkSocket in gmoccapy - that is X11-only, CasildaCompositor probably can help here ], but at least Gremlin is now ready for this move.

[rene-dev]

What is gtksocket used for?

[alex-pres]

What is gtksocket used for?

AI generated:

Verdict

Nothing in the tree runs under native Wayland by default — scripts/linuxcnc forces the X11 backend for every toolkit before any GUI starts. Even with that override removed, the Tk half of LinuxCNC (AXIS, tklinuxcnc, PyVCP, vismach, halshow, tooledit, ngcgui…) can never run natively, and the XEmbed panel system (EMBED_TAB_COMMAND) is X11-protocol by definition.

Only the Qt (qtvcp) family and the GTK3 GUIs without embedded tabs are close to native-capable.

---

S1 — Hard blockers (no Wayland path exists)

1. The launcher pins everything to X11

scripts/linuxcnc.in:30

if [[ ! -v LINUXCNC_OPENGL_PLATFORM || "${LINUXCNC_OPENGL_PLATFORM}" == "glx" ]]; then
    export PYOPENGL_PLATFORM="x11"
    export GDK_BACKEND="x11"
    export QT_QPA_PLATFORM="xcb"
fi

Default path forces XWayland for GTK, Qt and PyOpenGL simultaneously. There is no wayland/egl branch — LINUXCNC_OPENGL_PLATFORM is only consumed here and in the test rig (tests/ui-smoke/_lib/qtdragon-prepare.sh:46, which sets offscreen).

2. Tk/Tkinter has no Wayland backend — and it is the primary GUI

AXIS is the default GUI (16 of the sim configs; tklinuxcnc 4 more). Tk 8.6/9.0 on Linux is X11-only upstream; there is no port. Affected entry points found in-tree:

Component	File
AXIS	src/emc/usr_intf/axis/scripts/axis.py
Togl GL widget (C, GLX+Xlib)	src/emc/usr_intf/axis/extensions/togl.c
tklinuxcnc	tcl/tklinuxcnc.tcl
PyVCP	src/hal/user_comps/pyvcp.py:44
vismach (all 15 machine GUIs)	lib/python/vismach.py:19 → lib/python/rs274/OpenGLTk.py:16
halshow / halconfig / genedit / popimage	tcl/bin/*.tcl
tooledit, ngcgui, pickconfig, moveoff_gui	tcl/*.tcl, scripts/moveoff_gui
hal_manualtoolchange, linuxcnctop, debuglevel, teach-in, image-to-gcode, axis-remote	src/emc/usr_intf/axis/scripts/
latency-histogram, latency-plot, mdro, monitor-xhc-hb04	scripts/, src/emc/usr_intf/mdro/
update_ini (the INI-version upgrade GUI)	src/emc/ini/update_ini.py
qtplasmac's G-code dialog (Tk inside a Qt app)	src/emc/usr_intf/qtplasmac/qtplasmac_gcode.py:1571

Togl specifics: 28 glX* calls, direct X11/Xlib.h, XCreateWindow, XCreateColormap, XmuLookupStandardColormap, XSGIStereo*. Links -lX11 -lXmu -lGL (src/emc/usr_intf/axis/Submakefile:24).

3. XEmbed — the entire EMBED_TAB_COMMAND / -x {XID} panel system

Wayland has no cross-process window embedding. Every panel-in-GUI feature is X11 protocol:

• AXIS host side: axis.py:4101 xid = gladevcp_frame.winfo_id(), axis.py:4204 c.replace('{XID}', str(xid)).
• GladeVCP client side: lib/python/gladevcp/xembed.py:22 Gtk.Plug.new(), raw python-xlib _XEMBED_INFO property + w.reparent().
• QtVCP client side: lib/python/qtvcp/lib/xembed.py:34 int(window.winId()) + Xlib reparent; invoked at src/emc/usr_intf/qtvcp/qtvcp.py:396.
• GTK host side: Gtk.Socket (removed in GTK4, X11-only in GTK3) — gmoccapy.py:1854, gmoccapy.py:2347, gscreen.py:3167, gscreen.py:3926, touchy.py:1230.
• QtVCP XEmbed widget shipped in screens (x1mill.ui:8267): lib/python/qtvcp/widgets/xembed.py.

4. Synthetic key-event forwarding between processes

AXIS_FORWARD_EVENTS_TO carries AXIS's root XID (axis.py:4182); embedded panels push synthetic XKeyPress into it via Xlib send_event — gladevcp/xembed.py:106, qtvcp/lib/xembed.py:56. Wayland forbids one client injecting input into another. No replacement exists.

5. On-screen keyboard integration

onboard --xid / matchbox-keyboard --xid + Gtk.Socket.add_id() — gmoccapy.py:2336, gscreen.py:3138. Both the --xid handshake and the socket are X11. (QtVCP has a native fallback: lib/python/qtvcp/lib/virtual_keyboard.py.)

6. Tk send IPC

axis-remote drives AXIS entirely through Tk's send, which is X11-only (SendCommand over X properties): axis-remote.py:87-101. Also axis.py:4162 and scripts/linuxcnc.in:249 (send -async popimage destroy .).

---

S2 — Functional breakage (app starts, feature silently dead)

Item	Location	Wayland behaviour
xhost -SI:localuser:gdm -SI:localuser:root at AXIS import	axis.py:142	no-op / error
same in ngcgui	tcl/ngcgui.tcl:2762	no-op
xset -r <keycode> to kill autorepeat for jogging	qt_action.py:854	no-op; uneven jog repeat returns
Tk detectable-autorepeat (XkbSetDetectableAutoRepeat)	tkdarmodule.c	X-only by construction
Xinerama multihead query for screen layout	emcsh.cc:3584, linked -lXinerama (Submakefile:25)	X-only
d.warp_pointer() (touchy invisible-cursor hack)	touchy.py:1226	unsupported on GDK Wayland
Absolute window placement window1.move(x, y)	gmoccapy.py:3343, :5334, :5340, :5349, :5357; gscreen.py:1622	ignored — no client-side positioning
Notification popup placement	gmoccapy/notification.py:204, :283	ignored
w.get_origin() for dialog placement	gscreen.py:2387	returns garbage/0
halmeter -g x y	src/hal/utils/meter.c:316 gtk_window_move	ignored
QtVCP -g +x+y	qtvcp.py:417 window.move()	ignored
QtVCP --always-top	qtvcp.py:438 WindowStaysOnTopHint	ignored (no protocol)
Tk wm attributes -topmost / overrideredirect / +x+y	tcl/bin/halshow.tcl:105,1201,1511, tcl/bin/popimage:79, tcl/scripts/balloon.tcl:104	X-only
cv2.imshow camera windows	set_offsets.py:275	OpenCV highgui is X11 on Debian

---

S3 — Packaging / build

• debian/control has no qtwayland5 / libqt5waylandclient5 dependency → QT_QPA_PLATFORM=wayland fails on a stock install even for qtvcp.
• Hard build deps on X: AC_PATH_XTRA, X11/extensions/Xinerama.h (mandatory), X11/Xmu/Xmu.h (mandatory, error if missing) — src/configure.ac:1569, :1576, :1743.
• Runtime deps: python3-xlib, x11-xserver-utils, x11-utils, tcl8.6/tk8.6 — debian/control:41,47, debian/control.main-pkg.in:24,37.
• All UI tests run under xvfb-run (tests/ui-smoke/_lib/launch.sh:61); tests/ui-smoke/_lib/window-fit.sh requires xwininfo. There is zero Wayland test coverage in-tree.

---

Already Wayland-clean

• gremlin GTK preview — ported to Gtk.GLArea on this branch (d79f87ed67, gremlin.py:93); all GLX/Xlib/GdkX11 removed, EGL via GDK.
• qtvcp preview — QOpenGLWidget (qt5_graphics.py:224).
• qt_vismach — QOpenGLWidget (qt_vismach.py:67), unlike Tk vismach.
• halmeter / halscope / miscgtk — plain GTK3 C, no X calls (only the -g placement above).
• stepconf / pncconf, gladevcp standalone (no -x) — plain GTK3.

---

Minimum viable native-Wayland target

gmoccapy / touchy / gscreen / qtvcp without EMBED_TAB_* and without onboard, after: dropping the GDK_BACKEND/QT_QPA_PLATFORM force in scripts/linuxcnc.in, adding qtwayland5 to debian/control, and accepting that window placement, always-on-top and xset autorepeat become no-ops.

AXIS, tklinuxcnc, PyVCP, vismach and all XEmbed panels stay on XWayland until they are rehosted on a non-Tk toolkit and the panel system is replaced with in-process loading (GTK4/Qt) or a Wayland subsurface protocol.