Window decorations missing completely on certain WMs

[rmottola]

On WindowMaker all is fine.
On special X11 MS-Windows native windowmanager exported GNUstep windows lack any control, windows are impossible to close, move,ecc.

Windows from GTK, Athena, ecc all work fine.

PS: this is not win32 backend, but X11.

[DTW-Thalion]

@rmottola, which X server and mode is this (Cygwin/X XWin -multiwindow, VcXsrv -multiwindow, X410, …), and its version? That decides whether the server reads _MOTIF_WM_HINTS at all.

On non-WindowMaker WMs the X11 backend stops using _GNUSTEP_WM_ATTR and asks the WM to decorate via _MOTIF_WM_HINTS (XGServerWindow.m:908). A couple of things would pin down where that breaks:

1. Run an affected app with --GNU-Debug=WM and paste the WM Protocols: WindowMaker=(..) GNOME=(..) EWMH=(..) line, so we know how _checkWindowManager classifies this WM.
2. xprop _MOTIF_WM_HINTS on an undecorated GNUstep window and on a working GTK window, for comparison.
3. Is GSBackHandlesWindowDecorations (or GSX11HandlesWindowDecorations) set in your defaults? As a test, defaults write NSGlobalDomain GSBackHandlesWindowDecorations NO and relaunch — if GNUstep then draws its own title bar and controls, that isolates it to the WM-side decoration path.

Unfortunately I don't have this configuration available so I can't help much debug this.

[rmottola]

@DTW-Thalion I am using (a slightly old version of) MobaXTerm . it should be based on Cygwin. I will see if I can get the details.
This bug could be a little related to #84 which is also an issues on rootless. There however styles come from window levels.
I also use X11.app on Mac which is rootless but more up-to-date. Will re-check.

[DTW-Thalion]

@rmottola any luck here?

[DTW-Thalion]

Measured this against a window manager written to map windows and decorate
nothing, which is how a rootless X server driving a native window manager can
behave.

The hints GNUstep sets are correct. On a titled, closable, miniaturizable and
resizable window _MOTIF_WM_HINTS holds 0x3, 0x3e, 0x6e: flags for functions
and decorations, functions for resize, move, minimize, maximize and close, and
decorations for border, resize handle, title, minimize and maximize.
_GNUSTEP_WM_ATTR is set as well. So the request is not what is missing.

What is missing is that nothing checks the result. Whether the backend or the
gui library draws the title bar and the buttons is decided by the method
named -handlesWindowDecorations, which answered YES whatever the window
manager did, changing only for the GSBackHandlesWindowDecorations default. PR #228
answers it from the offsets probe instead: a window manager that puts a border
on no style at all draws no title bar either. Under that window manager a
titled window was 200x120, the content rect asked for, and becomes 202x144,
with a title bar and buttons drawn by the gui library.

One more thing came out of it. With no decoration on any style the offsets
probe fails for every style, so the offsets are never stored on the root
window and every application start repeats the probe, about a second per
style.

The xprop and --GNU-Debug=WM output asked for above would still confirm this is
the same case, rather than a window manager that decorates in some other way.

[rmottola]

Debug output. Apparently plain window manager with no protocols

SystemPreferences --GNU-Debug=WM
2026-08-07 09:34:31.932 SystemPreferences[823886:823886] Failed to get _NET_WORKAREA
2026-08-07 09:34:31.953 SystemPreferences[823886:823886] WM Protocols: WindowMaker=(NO) GNOME=(NO) EWMH=(NO)
2026-08-07 09:34:31.987 SystemPreferences[823886:823886] Failed to get _NET_WORKAREA

% xprop
WM_STATE(WM_STATE):
                window state: Normal
                icon window: 0x0
_WINDOWSWM_NATIVE_HWND(INTEGER) = 132190
WM_HINTS(WM_HINTS):
                Client accepts input or input focus: False
                window id # of group leader: 0x200001
WM_NORMAL_HINTS(WM_SIZE_HINTS):
                user specified location: 189, 296
                program specified location: 189, 296
                user specified size: 592 by 414
                program specified size: 592 by 414
                program specified minimum size: 592 by 414
                program specified maximum size: 592 by 414
_NET_WM_ICON_NAME(UTF8_STRING) = "System Preferences"
_NET_WM_NAME(UTF8_STRING) = "System Preferences"
WM_ICON_NAME(UTF8_STRING) = "System Preferences"
WM_NAME(UTF8_STRING) = "System Preferences"
WM_PROTOCOLS(ATOM): protocols  WM_TAKE_FOCUS, WM_DELETE_WINDOW
_NET_WM_SYNC_REQUEST_COUNTER(CARDINAL) = 2097189
_MOTIF_WM_HINTS(_MOTIF_WM_HINTS) = 0x3, 0x2c, 0x2a, 0x0, 0x0
_GNUSTEP_WM_ATTR(_GNUSTEP_WM_ATTR) = 0x83, 0x7, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x20, 0x0, 0xffffff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0
WM_CLASS(STRING) = "SystemPreferences", "SystemPreferences"

Here emacs.
Left in the encoded icon because it is cool and we should do it too 😄

Maybe the significant difference is: _NET_WM_WINDOW_TYPE(ATOM) = _NET_WM_WINDOW_TYPE_NORMAL

% xprop
_NET_WM_USER_TIME(CARDINAL) = 32365574
_MOTIF_DRAG_RECEIVER_INFO(_MOTIF_DRAG_RECEIVER_INFO) = 0x6c, 0x0, 0x5, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0
_NET_WM_OPAQUE_REGION(CARDINAL) = 0, 0, 672, 605
_WINDOWSWM_NATIVE_HWND(INTEGER) = 263268
WM_HINTS(WM_HINTS):
                Client accepts input or input focus: True
                Initial state is Normal State.
                bitmap id # to use for icon: 0x2801ca
                bitmap id # of mask for icon: 0x2801d0
                window id # of group leader: 0x280001
_GTK_THEME_VARIANT(UTF8_STRING) =
WM_STATE(WM_STATE):
                window state: Normal
                icon window: 0x0
_NET_WM_ICON(CARDINAL) =        Icon (48 x 48):

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XdndAware(ATOM) = BITMAP
_NET_WM_WINDOW_TYPE(ATOM) = _NET_WM_WINDOW_TYPE_NORMAL
_NET_WM_SYNC_REQUEST_COUNTER(CARDINAL) = 2621763, 2621764
_NET_WM_USER_TIME_WINDOW(WINDOW): window id # 0x280142
WM_CLIENT_LEADER(WINDOW): window id # 0x280001
_NET_WM_PID(CARDINAL) = 824035
WM_LOCALE_NAME(STRING) = "C"
WM_CLIENT_MACHINE(STRING) = "moria"
WM_NORMAL_HINTS(WM_SIZE_HINTS):
                program specified minimum size: 40 by 150
                program specified resize increment: 8 by 15
                program specified base size: 40 by 80
                window gravity: NorthWest
WM_PROTOCOLS(ATOM): protocols  WM_DELETE_WINDOW, WM_TAKE_FOCUS, _NET_WM_PING, _NET_WM_SYNC_REQUEST
WM_CLASS(STRING) = "emacs", "Emacs"
WM_ICON_NAME(STRING) = "*scratch* - GNU Emacs at moria"
_NET_WM_ICON_NAME(UTF8_STRING) = "*scratch* - GNU Emacs at moria"
WM_NAME(STRING) = "*scratch* - GNU Emacs at moria"
_NET_WM_NAME(UTF8_STRING) = "*scratch* - GNU Emacs at moria"