Move flow_percentage to Planner

Marlin/src/Marlin.cpp

 FORCE_INLINE float homing_feedrate(const AxisEnum a) { return pgm_read_float(&homing_feedrate_mm_s[a]); }
 
 static float saved_feedrate_mm_s;
-int16_t feedrate_percentage = 100, saved_feedrate_percentage,
-    flow_percentage[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(100);
+int16_t feedrate_percentage = 100, saved_feedrate_percentage;
 
 // Initialized by settings.load()
 bool volumetric_enabled;

Marlin/src/Marlin.h

 #define MMS_SCALED(MM_S) ((MM_S)*feedrate_percentage*0.01)
 
 extern bool volumetric_enabled;
-extern int16_t flow_percentage[EXTRUDERS]; // Extrusion factor for each extruder
 extern float filament_size[EXTRUDERS]; // cross-sectional area of filament (in millimeters), typically around 1.75 or 2.85, 0 disables the volumetric calculations for the extruder.
 extern float volumetric_multiplier[EXTRUDERS]; // reciprocal of cross-sectional area of filament (in square millimeters), stored this way to reduce computational burden in planner
 

Marlin/src/feature/fwretract.cpp

 FWRetract fwretract; // Single instance
 
 #include "../module/motion.h"
+#include "../module/planner.h"
 
 bool FWRetract::autoretract_enabled,                 // M209 S - Autoretract switch
      FWRetract::retracted[EXTRUDERS] = { false };    // Which extruders are currently retracted
   const bool has_zhop = retract_zlift > 0.01;     // Is there a hop set?
 
   const float old_feedrate_mm_s = feedrate_mm_s;
-  const int16_t old_flow = flow_percentage[active_extruder];
+  const int16_t old_flow = planner.flow_percentage[active_extruder];
 
   // Don't apply flow multiplication to retract/recover
-  flow_percentage[active_extruder] = 100;
+  planner.flow_percentage[active_extruder] = 100;
 
   // The current position will be the destination for E and Z moves
   set_destination_to_current();
   }
 
   // Restore flow and feedrate
-  flow_percentage[active_extruder] = old_flow;
+  planner.flow_percentage[active_extruder] = old_flow;
   feedrate_mm_s = old_feedrate_mm_s;
 
   // The active extruder is now retracted or recovered

Marlin/src/gcode/config/M221.cpp

  */
 
 #include "../gcode.h"
-#include "../../Marlin.h"
+#include "../../module/planner.h"
 
 /**
  * M221: Set extrusion percentage (M221 T0 S95)
 void GcodeSuite::M221() {
   if (get_target_extruder_from_command()) return;
   if (parser.seenval('S'))
-    flow_percentage[target_extruder] = parser.value_int();
+    planner.flow_percentage[target_extruder] = parser.value_int();
 }

Marlin/src/gcode/sensor/M405.h

   //SERIAL_PROTOCOLPGM("Filament dia (measured mm):");
   //SERIAL_PROTOCOL(filament_width_meas);
   //SERIAL_PROTOCOLPGM("Extrusion ratio(%):");
-  //SERIAL_PROTOCOL(flow_percentage[active_extruder]);
+  //SERIAL_PROTOCOL(planner.flow_percentage[active_extruder]);
 }

Marlin/src/lcd/ultralcd.cpp

     // Flow [1-5]:
     //
     #if EXTRUDERS == 1
-      MENU_ITEM_EDIT(int3, MSG_FLOW, &flow_percentage[0], 10, 999);
+      MENU_ITEM_EDIT(int3, MSG_FLOW, &planner.flow_percentage[0], 10, 999);
     #else // EXTRUDERS > 1
-      MENU_ITEM_EDIT(int3, MSG_FLOW, &flow_percentage[active_extruder], 10, 999);
-      MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N1, &flow_percentage[0], 10, 999);
-      MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N2, &flow_percentage[1], 10, 999);
+      MENU_ITEM_EDIT(int3, MSG_FLOW, &planner.flow_percentage[active_extruder], 10, 999);
+      MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N1, &planner.flow_percentage[0], 10, 999);
+      MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N2, &planner.flow_percentage[1], 10, 999);
       #if EXTRUDERS > 2
-        MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N3, &flow_percentage[2], 10, 999);
+        MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N3, &planner.flow_percentage[2], 10, 999);
         #if EXTRUDERS > 3
-          MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N4, &flow_percentage[3], 10, 999);
+          MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N4, &planner.flow_percentage[3], 10, 999);
           #if EXTRUDERS > 4
-            MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N5, &flow_percentage[4], 10, 999);
+            MENU_ITEM_EDIT(int3, MSG_FLOW MSG_N5, &planner.flow_percentage[4], 10, 999);
           #endif // EXTRUDERS > 4
         #endif // EXTRUDERS > 3
       #endif // EXTRUDERS > 2

Marlin/src/module/planner.cpp

   uint8_t Planner::last_extruder = 0;     // Respond to extruder change
 #endif
 
+int16_t Planner::flow_percentage[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(100); // Extrusion factor for each extruder
+
 uint32_t Planner::max_acceleration_steps_per_s2[XYZE_N],
          Planner::max_acceleration_mm_per_s2[XYZE_N]; // Use M201 to override by software
 

Marlin/src/module/planner.h

       static uint8_t last_extruder;             // Respond to extruder change
     #endif
 
+    static int16_t flow_percentage[EXTRUDERS];  // Extrusion factor for each extruder
+
     static float max_feedrate_mm_s[XYZE_N],     // Max speeds in mm per second
                  axis_steps_per_mm[XYZE_N],
                  steps_to_mm[XYZE_N];