i3: Fix opening kitty in the current working dir

Since I run kitty with --single-instance, xcwd does not work for it.
Replace it with a short script that retrieves the CWD for the focused
window through the remote-control ls command.

This changes the current behaviour slightly, since now only terminals
are used and not any X window (which I rarely used or needed) and that
the working dir of the shell running in kitty will be used and not of
any deeper children. I'm still unsure if I want the latter back, but
will figure this out in the future.

This is an addendum to 0139294831 ("Use kitty instead of st as
terminal").

.config/i3/config

@@ -38,8 +38,14 @@ set $TERM_CMD_FLAG
 # For this to work best, launch one hidden "daemon" instance at startup so that
 # the kitty process is always running, even when no OS windows exists.
 #
+# Additionally allow remote_control over a socket, so that kitty-cwd works.
+#
 # [^1]: kitty(1)
-exec --no-startup-id $TERMINAL --start-as hidden --detach
+exec --no-startup-id $TERMINAL \
+	--start-as hidden \
+	--detach \
+	-o allow_remote_control=socket-only \
+	--listen-on unix:/tmp/mykitty
 
 # Multi monitor support
 exec_always --no-startup-id ~/.config/i3/monitor-setup.sh &
@@ -47,7 +53,7 @@ exec_always --no-startup-id ~/.config/i3/monitor-setup.sh &
 # Keybindins ###################################################################
 
 # Terminal
-bindsym $mod+Return       exec $TERMINAL $TERM_DIR_FLAG "$(xcwd)"
+bindsym $mod+Return       exec $TERMINAL $TERM_DIR_FLAG "$(kitty-cwd)"
 bindsym $mod+Shift+Return exec $TERMINAL
 
 # Program launcher
@@ -231,7 +237,7 @@ bindsym $mod+comma exec \
 	i3-msg '[class="^$TERM_CLASS$" title="^scratchpad-terminal$"] \
 	        scratchpad show' \
 	|| $TERMINAL $TERM_TRANSPARENCY_FLAG$TERM_SCRATCHPAD_TRANS \
-	             $TERM_DIR_FLAG "$(xcwd)" \
+	             $TERM_DIR_FLAG "$(kitty-cwd)" \
 	             $TERM_TITLE_FLAG scratchpad-terminal
 
 for_window [class="^TelegramDesktop$"] \

.config/kitty/get_cwd.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+# SPDX-License-Identifier: MIT
+# Copyright (c) 2025 Julian Prein
+#
+# Print the current working directory of the focused kitty window. Returns 4 if
+# none exist or is focused.
+
+# NOTE: the backticks are used for hacky line-continuation, taken from
+#       https://stackoverflow.com/a/7729087/2092762c9
+kitten @ --to unix:/tmp/mykitty ls \
+	| jq -er ".[]`
+		` | select(.is_focused).tabs.[]`
+		` | select(.is_focused).windows.[]`
+		` | select(.is_focused).cwd"
+
+# An alternative version that uses recursive descent to find focused objects
+# that also have a `.cwd` key:
+#
+#	| jq -er "..`
+#		` | objects`
+#		` | select(.is_focused)`
+#		` | to_entries.[]`
+#		` | select(.key == \"cwd\").value"

.local/bin/kitty-cwd

@@ -0,0 +1 @@
+/home/user/projs/dotfiles/.config/kitty/get_cwd.sh