zfsbootmenu: add modal power menu on main screen

docs/online/main-screen.rst

@@ -66,3 +66,7 @@ Keyboard Shortcuts
 *[MOD+L]* **view logs**
 
   View logs, as indicated by *[!]*. The indicator will be yellow for warning conditions and red for errors.
+
+*[MOD+X]* **power menu**
+
+  Show menu with options to shutdown, reboot, or reboot to UEFI firmware setup (if available).

zfsbootmenu/bin/zfsbootmenu

@@ -282,5 +282,8 @@ while true; do
     "mod-o")
       change_sort
       ;;
+    "mod-x")
+      /libexec/zpowermenu
+      ;;
   esac
 done

zfsbootmenu/lib/zfsbootmenu-ui.sh

@@ -148,9 +148,9 @@ draw_be() {
   fi
 
   header="$( column_wrap "\
-^[RETURN] boot:[ESCAPE] refresh view:[CTRL+P] pool status
-^[CTRL+D] set bootfs:[CTRL+S] snapshots:[CTRL+K] kernels
-^[CTRL+E] edit kcl:[CTRL+J] jump into chroot:[CTRL+R] recovery shell
+^[RETURN] boot:[CTRL+K] kernels:[CTRL+P] pool status
+^[CTRL+D] set bootfs:[CTRL+R] recovery shell:[CTRL+S] snapshots
+^[CTRL+E] edit kcl:[CTRL+J] jump into chroot:[CTRL+X] power menu
 ^${kcl_text:+${kcl_text}:}[CTRL+L] view logs:${blank}[CTRL+H] help" \
 "\
 ^[RETURN] boot
@@ -160,7 +160,7 @@ draw_be() {
   sort_key="$( get_sort_key )"
   preview_label="Sorted by: ${sort_key^}"
 
-  expects="--expect=alt-e,alt-k,alt-d,alt-s,alt-c,alt-r,alt-p,alt-w,alt-j,alt-o${kcl_bind:+,${kcl_bind}},right"
+  expects="--expect=alt-e,alt-k,alt-d,alt-s,alt-c,alt-r,alt-p,alt-w,alt-j,alt-o,alt-x${kcl_bind:+,${kcl_bind}},right"
 
   # shellcheck disable=SC2086
   if ! selected="$( ${FUZZYSEL} -0 --prompt "BE > " \

zfsbootmenu/libexec/zpowermenu

@@ -0,0 +1,14 @@
+#!/bin/bash
+# vim: softtabstop=2 shiftwidth=2 expandtab
+
+source /lib/efi-firmware-lib.sh >/dev/null 2>&1 || exit 1
+source /lib/zfsbootmenu-ui.sh >/dev/null 2>&1 || exit 1
+
+PROMPT=("/bin/poweroff:Shutdown" "/bin/reboot:Reboot")
+if check_fw_setup; then
+    PROMPT+=("/bin/firmware-setup:Reboot to UEFI Firmware")
+fi
+
+if execute="$(draw_modal_prompt "Power Menu" "${PROMPT[@]}")" && [ -x "$execute" ]; then
+    exec "$execute"
+fi