1 files changed, 36 insertions, 0 deletions
diff --git a/tmuxrdr/plugin/bin/track-focus b/tmuxrdr/plugin/bin/track-focus
new file mode 100755
index 00000000..4132891f
--- /dev/null
+++ b/tmuxrdr/plugin/bin/track-focus
@@ -0,0 +1,36 @@
+#!/bin/sh
+# Event hook for tab.focused and workspace.focused: keeps the current and
+# previous tab of each workspace, and the current and previous workspace, so
+# `last window` and `last session` know where to go. Hooks run concurrently,
+# so updates take a mkdir lock.
+. "$(dirname "$0")/../lib.sh"
+
+dir="$(state_dir)"
+ev="${HERDR_PLUGIN_EVENT_JSON:-}"
+[ -n "$ev" ] || exit 0
+
+field() {
+    printf '%s' "$ev" | jq -r --arg k "$1" '[.. | objects | .[$k]? | strings][0] // empty'
+}
+
+# record NAME VALUE: VALUE becomes NAME.current, the old one NAME.previous.
+record() {
+    [ -n "$2" ] || return 0
+    cur="$(cat "$dir/$1.current" 2>/dev/null || true)"
+    [ "$cur" = "$2" ] && return 0
+    [ -n "$cur" ] && printf '%s\n' "$cur" >"$dir/$1.previous"
+    printf '%s\n' "$2" >"$dir/$1.current"
+}
+
+tries=0
+until mkdir "$dir/.lock" 2>/dev/null; do
+    tries=$((tries + 1))
+    [ "$tries" -gt 40 ] && break
+    sleep 0.05
+done
+trap 'rmdir "$dir/.lock" 2>/dev/null' EXIT
+
+case "${HERDR_PLUGIN_EVENT:-}" in
+tab.focused) record "tab.$(key_of "$(field workspace_id)")" "$(field tab_id)" ;;
+workspace.focused) record workspace "$(field workspace_id)" ;;
+esac