Add Debug Menu with LCD_PROGRESS_BAR_TEST as an example

Marlin/Conditionals_LCD.h

     #define BOOTSCREEN_TIMEOUT 2500
   #endif
 
+  #define HAS_DEBUG_MENU ENABLED(LCD_PROGRESS_BAR_TEST)
+
   /**
    * Extruders have some combination of stepper motors and hotends
    * so we separate these concepts into the defines:

Marlin/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/Cartesio/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/Felix/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/Hephestos/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/Hephestos_2/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/K8200/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/K8400/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/RigidBot/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/SCARA/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/TAZ4/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/WITBOX/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/delta/biv2.5/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/delta/generic/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/delta/kossel_mini/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/delta/kossel_pro/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/delta/kossel_xl/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/makibox/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/example_configurations/tvrrug/Round2/Configuration_adv.h

     #define PROGRESS_MSG_EXPIRE   0
     // Enable this to show messages for MSG_TIME then hide them
     //#define PROGRESS_MSG_ONCE
+    // Add a menu item to test the progress bar:
+    //#define LCD_PROGRESS_BAR_TEST
   #endif
 
   // This allows hosts to request long names for files and folders with M33

Marlin/language_en.h

 #ifndef MSG_DISABLE_STEPPERS
   #define MSG_DISABLE_STEPPERS                _UxGT("Disable steppers")
 #endif
+#ifndef MSG_DEBUG_MENU
+  #define MSG_DEBUG_MENU                      _UxGT("Debug Menu")
+#endif
+#ifndef MSG_PROGRESS_BAR_TEST
+  #define MSG_PROGRESS_BAR_TEST               _UxGT("Progress Bar Test")
+#endif
 #ifndef MSG_AUTO_HOME
   #define MSG_AUTO_HOME                       _UxGT("Auto home")
 #endif

Marlin/ultralcd.cpp

   #define MENU_BACK(LABEL) MENU_ITEM(back, LABEL, 0)
 
   // Used to print static text with no visible cursor.
+  // Parameters: label [, bool center [, bool invert [, char *value] ] ]
   #define STATIC_ITEM(LABEL, ...) \
     if (_menuLineNr == _thisItemNr) { \
       if (_skipStatic && encoderLine <= _thisItemNr) { \
 
   #endif // MENU_ITEM_CASE_LIGHT
 
+  #if ENABLED(LCD_PROGRESS_BAR_TEST)
+
+    static void progress_bar_test() {
+      static int8_t bar_percent = 0;
+      if (lcd_clicked) {
+        lcd_goto_previous_menu();
+        lcd_set_custom_characters(false);
+        return;
+      }
+      bar_percent += (int8_t)encoderPosition;
+      bar_percent = constrain(bar_percent, 0, 100);
+      encoderPosition = 0;
+      lcd_implementation_drawmenu_static(0, PSTR(MSG_PROGRESS_BAR_TEST), true, true);
+      lcd.setCursor((LCD_WIDTH) / 2 - 2, LCD_HEIGHT - 2);
+      lcd.print(itostr3(bar_percent)); lcd.print('%');
+      lcd.setCursor(0, LCD_HEIGHT - 1); lcd_draw_progress_bar(bar_percent);
+    }
+
+    void _progress_bar_test() {
+      lcd_goto_screen(progress_bar_test);
+      lcd_set_custom_characters();
+    }
+
+  #endif // LCD_PROGRESS_BAR_TEST
+
+  #if HAS_DEBUG_MENU
+
+    void lcd_debug_menu() {
+      START_MENU();
+
+      MENU_BACK(MSG_MAIN); // ^ Main
+
+      #if ENABLED(LCD_PROGRESS_BAR_TEST)
+        MENU_ITEM(submenu, MSG_PROGRESS_BAR_TEST, _progress_bar_test);
+      #endif
+
+      END_MENU();
+    }
+
+  #endif // HAS_DEBUG_MENU
+
   /**
    *
    * "Main" menu
     MENU_BACK(MSG_WATCH);
 
     //
+    // Debug Menu when certain options are enabled
+    //
+    #if HAS_DEBUG_MENU
+      MENU_ITEM(submenu, MSG_DEBUG_MENU, lcd_debug_menu);
+    #endif
+
+    //
     // Switch case light on/off
     //
     #if ENABLED(MENU_ITEM_CASE_LIGHT)

Marlin/ultralcd_impl_HD44780.h

   }
 }
 
+#if ENABLED(LCD_PROGRESS_BAR)
+
+  inline void lcd_draw_progress_bar(const uint8_t percent) {
+    int tix = (int)(percent * (LCD_WIDTH) * 3) / 100,
+      cel = tix / 3, rem = tix % 3, i = LCD_WIDTH;
+    char msg[LCD_WIDTH + 1], b = ' ';
+    msg[i] = '\0';
+    while (i--) {
+      if (i == cel - 1)
+        b = LCD_STR_PROGRESS[2];
+      else if (i == cel && rem != 0)
+        b = LCD_STR_PROGRESS[rem - 1];
+      msg[i] = b;
+    }
+    lcd.print(msg);
+  }
+
+#endif // LCD_PROGRESS_BAR
+
 /**
 Possible status screens:
 16x2   |000/000 B000/000|
     if (card.isFileOpen()) {
       // Draw the progress bar if the message has shown long enough
       // or if there is no message set.
-      if (ELAPSED(millis(), progress_bar_ms + PROGRESS_BAR_MSG_TIME) || !lcd_status_message[0]) {
-        int tix = (int)(card.percentDone() * (LCD_WIDTH) * 3) / 100,
-          cel = tix / 3, rem = tix % 3, i = LCD_WIDTH;
-        char msg[LCD_WIDTH + 1], b = ' ';
-        msg[i] = '\0';
-        while (i--) {
-          if (i == cel - 1)
-            b = LCD_STR_PROGRESS[2];
-          else if (i == cel && rem != 0)
-            b = LCD_STR_PROGRESS[rem - 1];
-          msg[i] = b;
-        }
-        lcd.print(msg);
-        return;
-      }
+      if (ELAPSED(millis(), progress_bar_ms + PROGRESS_BAR_MSG_TIME) || !lcd_status_message[0])
+        return lcd_draw_progress_bar(card.percentDone());
     } //card.isFileOpen
 
   #elif ENABLED(FILAMENT_LCD_DISPLAY)