From 13d1e26d696c5113a20dfc2f56c03ddb837a2eac Mon Sep 17 00:00:00 2001
From: Peter Hutterer <peter.hutterer@who-t.net>
Date: Mon, 12 Jul 2021 09:46:25 +1000
Subject: Check for Xwayland and print a warning

Running setxkbmap isn't supported by Xwayland, so let's warn the user that
this won't work.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Olivier Fourdan <ofourdan@redhat.com>
---
 configure.ac      |  3 ++-
 man/setxkbmap.man | 12 ++++++++++++
 setxkbmap.c       | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index d5733ff..9b475d3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -47,7 +47,8 @@ AC_ARG_WITH(xkb-config-root,
 AC_SUBST([XKBCONFIGROOT])
 
 # Checks for pkg-config packages
-PKG_CHECK_MODULES(SETXKBMAP, xkbfile x11)
+# xrandr is needed for the XWayland check
+PKG_CHECK_MODULES(SETXKBMAP, xkbfile x11 xrandr)
 
 # Allow checking code with lint, sparse, etc.
 XORG_WITH_LINT
diff --git a/man/setxkbmap.man b/man/setxkbmap.man
index 926b6f7..d02f25f 100644
--- a/man/setxkbmap.man
+++ b/man/setxkbmap.man
@@ -138,6 +138,18 @@ directly to the \fBxkbcomp\fP input.  For example, the command
 
 makes both steps run on the same (client) machine and loads a keyboard map into
 the server.
+
+.SH "XWAYLAND"
+Xwayland is an X server that uses a Wayland Compositor as backend.
+Xwayland acts as translation layer between the X protocol and the Wayland
+protocol but does not manage the keymaps - these are handled by the Wayland
+Compositor.
+.PP
+Changing the keymap with \fBsetxkbmap\fP is not supported by Xwayland.
+In most instances, using \fBsetxkbmap\fP on Xwayland is indicative of a
+bug in a shell script and \fBsetxkbmap\fP will print a warning. Use the Wayland
+Compositor's native XKB configuration methods instead.
+
 .SH SEE ALSO
 xkbcomp(__appmansuffix__), xkeyboard-config(__miscmansuffix__)
 .SH FILES
diff --git a/setxkbmap.c b/setxkbmap.c
index 3af641e..68eb9a6 100644
--- a/setxkbmap.c
+++ b/setxkbmap.c
@@ -38,6 +38,7 @@
 #include <X11/extensions/XKBfile.h>
 #include <X11/extensions/XKBconfig.h>
 #include <X11/extensions/XKBrules.h>
+#include <X11/extensions/Xrandr.h>
 
 #ifndef PATH_MAX
 #ifdef MAXPATHLEN
@@ -1067,12 +1068,59 @@ applyComponentNames(void)
     return True;
 }
 
+static Bool
+is_xwayland(void)
+{
+    /* Code copied from xisxwayland.c */
+    Bool rc = False;
+    XRRScreenResources *resources = NULL;
+    XRROutputInfo *output = NULL;
+
+    /* There is no definitive way of checking for an XWayland server,
+     * but the two working methods are:
+     * - RandR output names in Xwayland are XWAYLAND0, XWAYLAND1, etc.
+     * - XI devices are xwayland-pointer:10, xwayland-keyboard:11
+     * Let's go with the XRandR check here because it's slightly less
+     * code to write.
+     */
+
+    int event_base, error_base, major, minor;
+    if (!XRRQueryExtension(dpy, &event_base, &error_base) ||
+            !XRRQueryVersion(dpy, &major, &minor)) {
+        /* e.g. Xnest, but definitely not Xwayland */
+        goto out;
+    }
+
+    resources = XRRGetScreenResourcesCurrent(dpy, DefaultRootWindow(dpy));
+    if (!resources) {
+        goto out;
+    }
+
+    output = XRRGetOutputInfo(dpy, resources, resources->outputs[0]);
+    if (!output) {
+        goto out;
+    }
+
+    if (strncmp(output->name, "XWAYLAND", 8) == 0)
+        rc = True;
+
+    XRRFreeOutputInfo(output);
+out:
+    if (resources)
+        XRRFreeScreenResources(resources);
+
+    return rc;
+}
 
 int
 main(int argc, char **argv)
 {
     if ((!parseArgs(argc, argv)) || (!getDisplay(argc, argv)))
         exit(-1);
+
+    if (is_xwayland())
+	    MSG("WARNING: Running setxkbmap against an XWayland server\n");
+
     settings.locale.value = setlocale(LC_ALL, settings.locale.value);
     settings.locale.src = FROM_SERVER;
     VMSG1(7, "locale is %s\n", settings.locale.value);
-- 
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