Promote sxhkd watcher note to post

content/posts/sxkhd-watcher/index.md

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+---
+title: "Visualizing modal hotkeys in sxhkd"
+date: 2024-02-20T23:36:00+08:00
+lastmod:
+draft: false
+toc: true
+tags:
+- hotkeys
+- sxhkd
+---
+
+I use chord chains in [sxhkd](https://github.com/baskerville/sxhkd) to create
+modal hotkeys, similar to those in Vim. This allows the same key combination to
+be reused for different commands by prefixing it with a different chord,
+effectively creating custom "modes".
+
+From the sxhkd manpage:
+
+>When multiple chords are separated by semicolons, the hotkey is a chord chain:
+>the command will only be executed after receiving each chord of the chain in
+>consecutive order.
+
+For example, these are three hotkeys that use `super + h`, each prefixed with a
+different `super + [key]`:
+
+```bash
+# normal mode
+# focus the node in the given direction
+super + {h,j,k,l}
+    bspc node -f {west,south,north,east}
+
+# node mode
+# hide current window
+super + n : super + h
+    bspc node focused.window -g hidden=on
+
+# preselect mode
+# preselect in the given direction
+super + p : super + {h,j,k,l}
+    bspc node -p {west,south,north,east}
+```
+
+## Visualizing Custom Modes
+
+One issue with this workflow is that there is no visual indicator for the
+current activated "mode"; Vim has its status line to tell the user whether they
+are in `NORMAL`, `INSERT` or `VISUAL` mode.
+
+I often forget to leave the mode I had temporarily enabled, leading to
+accidental executions of random commands, which can be extremely frustrating.
+
+Thankfully, I discovered that `sxhkd` can output status information via a named
+pipe with the `-s` flag. We can poll this output with a watcher script and pair
+it with our bar of choice (`eww` for me) to show a visual indicator of the
+current sxhkd mode.
+
+## Implementation
+
+First, create a named pipe at `/var/run/user/[uid]/sxhkd.fifo`:
+
+```bash
+$ mkfifo /var/run/user/1000/sxhkd.fifo
+```
+
+Start `sxhkd` with the `-s` flag pointing at the new named pipe:
+
+```bash
+$ sxhkd -s /var/run/user/1000/sxhkd.fifo &
+```
+
+Restart `bspwm` and read from the named pipe file to check that it is
+working:
+
+```bash
+$ cat /var/run/user/1000/sxhkd.fifo
+```
+
+Pressing any `sxhkd` hotkeys will show the status information with this weird
+output:
+
+```bash
+Cbspc node -f east
+BBegin chain
+Hsuper + n
+EEnd chain
+BBegin chain
+Hsuper + p
+EEnd chain
+```
+
+A chord chain begins with `BBegin chain` and ends with `EEnd chain`. With this
+information, we can create a watcher script that reads from the named pipe and
+runs a custom command based on the output.
+
+For example, I would like to show that "node mode" is activated when `Hsuper +
+n` is pressed and deactivated when `EEnd chain` is outputted.
+
+```bash
+#!/bin/bash
+
+SXHKD_FIFO="/var/run/user/1000/sxhkd.fifo"
+cat $SXHKD_FIFO | while read line; do
+case ${line} in
+    # EEnd chain
+    E*)
+        echo "Normal mode" ;;
+    "Hsuper + n")
+        echo "Node mode" ;;
+    "Hsuper + p")
+        echo "Preselect mode" ;;
+   esac
+done
+```
+
+Finally, we poll this script with `polybar` or `eww` to show a visual
+indicator on the bar.
+
+{{< alert type="note" >}}
+To persist the named pipe at startup, initialize it in your `.xinitrc` file and
+ensure `sxhkd` starts up with the `-s` flag.
+{{< /alert >}}
+
+## References
+- [man - sxhkd](https://www.mankier.com/1/sxhkd)
+- [sxhkd - Allow running a command at start of colon chain](https://github.com/baskerville/sxhkd/issues/140)