✨ Power-off confirm / beep options (#22191)

Marlin/src/lcd/marlinui.cpp

@@ -1494,6 +1494,13 @@ void MarlinUI::update() {
     TERN_(HAS_LCD_MENU, return_to_status());
   }
 
+  #if BOTH(PSU_CONTROL, PS_OFF_CONFIRM)
+    void MarlinUI::poweroff() {
+      queue.inject_P(PSTR("M81"));
+      goto_previous_screen();
+    }
+  #endif
+
   void MarlinUI::flow_fault() {
     LCD_ALERTMESSAGEPGM(MSG_FLOWMETER_FAULT);
     TERN_(HAS_BUZZER, buzz(1000, 440));

Marlin/src/lcd/marlinui.h

@@ -334,6 +334,10 @@ public:
     static void resume_print();
     static void flow_fault();
 
+    #if BOTH(PSU_CONTROL, PS_OFF_CONFIRM)
+      static void poweroff();
+    #endif
+
     #if HAS_WIRED_LCD
 
       static millis_t next_button_update_ms;

Marlin/src/lcd/menu/menu_main.cpp

@@ -387,7 +387,15 @@ void menu_main() {
   //
   #if ENABLED(PSU_CONTROL)
     if (powersupply_on)
-      GCODES_ITEM(MSG_SWITCH_PS_OFF, PSTR("M81"));
+      #if ENABLED(PS_OFF_CONFIRM)
+        CONFIRM_ITEM(MSG_SWITCH_PS_OFF,
+          MSG_YES, MSG_NO,
+          ui.poweroff, ui.goto_previous_screen,
+          GET_TEXT(MSG_SWITCH_PS_OFF), (const char *)nullptr, PSTR("?")
+        );
+      #else
+        GCODES_ITEM(MSG_SWITCH_PS_OFF, PSTR("M81"));
+      #endif
     else
       GCODES_ITEM(MSG_SWITCH_PS_ON, PSTR("M80"));
   #endif