Resume Cthulhu on empty i3 workspaces

internal/platform/xorg/commands_native.c

@@ -312,7 +312,7 @@ int cthulhu_focus_metadata_unchecked(Display *display, SteamFocusSample *steam)
         steam->window = window;
     }
     if (window == None || window == root) {
-        return 0;
+        return cthulhu_i3_no_client_focus(display) ? 2 : 0;
     }
 
     Atom classAtom = XInternAtom(display, "WM_CLASS", False);

internal/platform/xorg/commands_native.h

@@ -37,6 +37,9 @@ typedef struct { int known, pid, steam, innerFocus; Window window, focus; } Stea
 typedef struct { int xterm; SteamFocusSample steam; } CommandFocusSample;
 
 int cthulhu_active_window_is_xterm(void);
+char *cthulhu_i3_socket(void);
+// Caller holds the X11 read guard and has confirmed no EWMH active client.
+int cthulhu_i3_no_client_focus(Display *display);
 int cthulhu_display_active_window_xterm_match(Display *display);
 Foreground read_foreground(Display *display);
 int cthulhu_xres_client_pids_supported(Display *display);

internal/platform/xorg/commands_owner_loop.go

@@ -136,7 +136,7 @@ func (owner *commandOwner) publishFocus() steamFocusSample {
 
 // Native xterm focus vetoes delayed accessibility requests to restore grabs.
 // lastFocusMatch belongs to this owner and survives unknown focus samples;
-// only a known non-xterm window ends the handoff.
+// only a known non-xterm window or verified i3 no-client focus ends the handoff.
 func (owner *commandOwner) commandGrabsAllowed() bool {
 	return owner.lastFocusMatch != 1 && owner.listener.commandsEnabled.Load() && !owner.listener.secure.Load()
 }

internal/platform/xorg/i3.go

@@ -6,46 +6,7 @@ package xorg
 
 /*
 #include "commands_native.h"
-#include <X11/Xlib.h>
-#include <X11/Xatom.h>
 #include <stdlib.h>
-#include <string.h>
-
-static unsigned char *i3_property(Display *d, Window w, const char *name, Atom wanted, int bits) {
-    Atom type; int format; unsigned long count, remaining;
-    unsigned char *value = NULL;
-    if (XGetWindowProperty(d, w, XInternAtom(d, name, False), 0, 1024, False,
-            wanted, &type, &format, &count, &remaining, &value) != Success ||
-            type != wanted || format != bits || remaining || !count) {
-        if (value) XFree(value);
-        return NULL;
-    }
-    return value;
-}
-
-static char *i3_socket(void) {
-    Display *d = XOpenDisplay(NULL);
-    if (!d) return NULL;
-    cthulhu_x11_begin_read(d);
-    char *socket = NULL;
-    Window root = DefaultRootWindow(d);
-    unsigned char *check = i3_property(d, root, "_NET_SUPPORTING_WM_CHECK", XA_WINDOW, 32);
-    if (check) {
-        Window wm = *(unsigned long *)check;
-        XFree(check);
-        unsigned char *self = i3_property(d, wm, "_NET_SUPPORTING_WM_CHECK", XA_WINDOW, 32);
-        unsigned char *name = i3_property(d, wm, "_NET_WM_NAME", XInternAtom(d, "UTF8_STRING", False), 8);
-        if (self && *(unsigned long *)self == wm && name && !strcmp((char *)name, "i3")) {
-            unsigned char *path = i3_property(d, root, "I3_SOCKET_PATH", XInternAtom(d, "UTF8_STRING", False), 8);
-            if (path) { socket = strdup((char *)path); XFree(path); }
-        }
-        if (self) XFree(self);
-        if (name) XFree(name);
-    }
-    if (cthulhu_x11_end_read(d)) { free(socket); socket = NULL; }
-    XCloseDisplay(d);
-    return socket;
-}
 */
 import "C"
 
@@ -61,7 +22,7 @@ func I3Socket() string {
 	if os.Getenv("DISPLAY") == "" {
 		return ""
 	}
-	path := C.i3_socket()
+	path := C.cthulhu_i3_socket()
 	if path == nil {
 		return ""
 	}

internal/platform/xorg/i3_native.c

@@ -0,0 +1,63 @@
+// Copyright (c) 2026 Storm Dragon
+// Authors: Storm Dragon, Angus Kola
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "commands_native.h"
+#include <X11/Xatom.h>
+#include <stdlib.h>
+#include <string.h>
+
+static unsigned char *i3_property(Display *d, Window w, const char *name, Atom wanted, int bits) {
+    Atom type; int format; unsigned long count, remaining;
+    unsigned char *value = NULL;
+    if (XGetWindowProperty(d, w, XInternAtom(d, name, False), 0, 1024, False,
+            wanted, &type, &format, &count, &remaining, &value) != Success ||
+            type != wanted || format != bits || remaining || !count) {
+        if (value) XFree(value);
+        return NULL;
+    }
+    return value;
+}
+
+// Caller holds the X11 read guard. Never trust an installed executable or an
+// inherited socket variable as evidence that i3 owns this display.
+static Window i3_support_window(Display *d) {
+    Window wm = None;
+    unsigned char *check = i3_property(d, DefaultRootWindow(d), "_NET_SUPPORTING_WM_CHECK", XA_WINDOW, 32);
+    if (check) {
+        Window candidate = *(unsigned long *)check;
+        XFree(check);
+        unsigned char *self = i3_property(d, candidate, "_NET_SUPPORTING_WM_CHECK", XA_WINDOW, 32);
+        unsigned char *name = i3_property(d, candidate, "_NET_WM_NAME", XInternAtom(d, "UTF8_STRING", False), 8);
+        if (self && *(unsigned long *)self == candidate && name && !strcmp((char *)name, "i3"))
+            wm = candidate;
+        if (self) XFree(self);
+        if (name) XFree(name);
+    }
+    return wm;
+}
+
+// Called only when EWMH explicitly reports no active client. i3 focuses its
+// support window on an empty workspace. Missing metadata or some other input
+// focus must preserve the previous handoff, rather than restoring grabs.
+int cthulhu_i3_no_client_focus(Display *d) {
+    Window wm = i3_support_window(d), focus = None;
+    if (wm == None) return 0;
+    int revert;
+    XGetInputFocus(d, &focus, &revert);
+    return focus == wm;
+}
+
+char *cthulhu_i3_socket(void) {
+    Display *d = XOpenDisplay(NULL);
+    if (!d) return NULL;
+    cthulhu_x11_begin_read(d);
+    char *socket = NULL;
+    if (i3_support_window(d) != None) {
+        unsigned char *path = i3_property(d, DefaultRootWindow(d), "I3_SOCKET_PATH", XInternAtom(d, "UTF8_STRING", False), 8);
+        if (path) { socket = strdup((char *)path); XFree(path); }
+    }
+    if (cthulhu_x11_end_read(d)) { free(socket); socket = NULL; }
+    XCloseDisplay(d);
+    return socket;
+}