Default Filament Runout Sensor enabled state (#19013)

Marlin/Configuration.h

  */
 //#define FILAMENT_RUNOUT_SENSOR
 #if ENABLED(FILAMENT_RUNOUT_SENSOR)
-  #define NUM_RUNOUT_SENSORS   1     // Number of sensors, up to one per extruder. Define a FIL_RUNOUT#_PIN for each.
-  #define FIL_RUNOUT_STATE     LOW   // Pin state indicating that filament is NOT present.
-  #define FIL_RUNOUT_PULLUP          // Use internal pullup for filament runout pins.
-  //#define FIL_RUNOUT_PULLDOWN      // Use internal pulldown for filament runout pins.
+  #define FIL_RUNOUT_ENABLED_DEFAULT true // Enable the sensor on startup. Override with M412 followed by M500.
+  #define NUM_RUNOUT_SENSORS   1          // Number of sensors, up to one per extruder. Define a FIL_RUNOUT#_PIN for each.
+  #define FIL_RUNOUT_STATE     LOW        // Pin state indicating that filament is NOT present.
+  #define FIL_RUNOUT_PULLUP               // Use internal pullup for filament runout pins.
+  //#define FIL_RUNOUT_PULLDOWN           // Use internal pulldown for filament runout pins.
 
   // Set one or more commands to execute on filament runout.
   // (After 'M412 H' Marlin will ask the host to handle the process.)

Marlin/src/feature/runout.cpp

   #include "../module/tool_change.h"
 #endif
 
-/**
- * Called by FilamentSensorSwitch::run when filament is detected.
- * Called by FilamentSensorEncoder::block_completed when motion is detected.
- */
-void FilamentSensorBase::filament_present(const uint8_t extruder) {
-  runout.filament_present(extruder); // calls response.filament_present(extruder)
-}
-
 #if HAS_FILAMENT_RUNOUT_DISTANCE
   float RunoutResponseDelayed::runout_distance_mm = FILAMENT_RUNOUT_DISTANCE_MM;
   volatile float RunoutResponseDelayed::runout_mm_countdown[EXTRUDERS];

Marlin/src/feature/runout.h

 
 void event_filament_runout();
 
+template<class RESPONSE_T, class SENSOR_T>
+class TFilamentMonitor;
+class FilamentSensorEncoder;
+class FilamentSensorSwitch;
+class RunoutResponseDelayed;
+class RunoutResponseDebounced;
+
+/********************************* TEMPLATE SPECIALIZATION *********************************/
+
+typedef TFilamentMonitor<
+          TERN(HAS_FILAMENT_RUNOUT_DISTANCE, RunoutResponseDelayed, RunoutResponseDebounced),
+          TERN(FILAMENT_MOTION_SENSOR, FilamentSensorEncoder, FilamentSensorSwitch)
+        > FilamentMonitor;
+
+extern FilamentMonitor runout;
+
+/*******************************************************************************************/
+
 class FilamentMonitorBase {
   public:
     static bool enabled, filament_ran_out;
 
 class FilamentSensorBase {
   protected:
-    static void filament_present(const uint8_t extruder);
+    /**
+     * Called by FilamentSensorSwitch::run when filament is detected.
+     * Called by FilamentSensorEncoder::block_completed when motion is detected.
+     */
+    static inline void filament_present(const uint8_t extruder) {
+      runout.filament_present(extruder); // ...which calls response.filament_present(extruder)
+    }
 
   public:
     static inline void setup() {
   };
 
 #endif // !HAS_FILAMENT_RUNOUT_DISTANCE
-
-/********************************* TEMPLATE SPECIALIZATION *********************************/
-
-typedef TFilamentMonitor<
-          TERN(HAS_FILAMENT_RUNOUT_DISTANCE, RunoutResponseDelayed, RunoutResponseDebounced),
-          TERN(FILAMENT_MOTION_SENSOR, FilamentSensorEncoder, FilamentSensorSwitch)
-        > FilamentMonitor;
-
-extern FilamentMonitor runout;

Marlin/src/module/settings.cpp

 
 #if HAS_FILAMENT_SENSOR
   #include "../feature/runout.h"
+  #ifndef FIL_RUNOUT_ENABLED_DEFAULT
+    #define FIL_RUNOUT_ENABLED_DEFAULT true
+  #endif
 #endif
 
 #if ENABLED(EXTRA_LIN_ADVANCE_K)
       #if HAS_FILAMENT_SENSOR
         const bool &runout_sensor_enabled = runout.enabled;
       #else
-        constexpr bool runout_sensor_enabled = true;
+        constexpr int8_t runout_sensor_enabled = -1;
       #endif
+      _FIELD_TEST(runout_sensor_enabled);
+      EEPROM_WRITE(runout_sensor_enabled);
+
       #if HAS_FILAMENT_RUNOUT_DISTANCE
         const float &runout_distance_mm = runout.runout_distance();
       #else
         constexpr float runout_distance_mm = 0;
       #endif
-      _FIELD_TEST(runout_sensor_enabled);
-      EEPROM_WRITE(runout_sensor_enabled);
       EEPROM_WRITE(runout_distance_mm);
     }
 
       // Filament Runout Sensor
       //
       {
-        #if HAS_FILAMENT_SENSOR
-          const bool &runout_sensor_enabled = runout.enabled;
-        #else
-          bool runout_sensor_enabled;
-        #endif
+        int8_t runout_sensor_enabled;
         _FIELD_TEST(runout_sensor_enabled);
         EEPROM_READ(runout_sensor_enabled);
+        #if HAS_FILAMENT_SENSOR
+          runout.enabled = runout_sensor_enabled < 0 ? FIL_RUNOUT_ENABLED_DEFAULT : runout_sensor_enabled;
+        #endif
 
         TERN_(HAS_FILAMENT_SENSOR, if (runout.enabled) runout.reset());
 
   //
 
   #if HAS_FILAMENT_SENSOR
-    runout.enabled = true;
+    runout.enabled = FIL_RUNOUT_ENABLED_DEFAULT;
     runout.reset();
     TERN_(HAS_FILAMENT_RUNOUT_DISTANCE, runout.set_runout_distance(FILAMENT_RUNOUT_DISTANCE_MM));
   #endif