Improve FWRETRACT logic, add common sense

Marlin/src/feature/fwretract.cpp

   #endif
 ) {
 
-  static float hop_height,        // Remember where the Z height started
-               hop_amount = 0.0;  // Total amount lifted, for use in recover
+  static float hop_amount = 0.0;  // Total amount lifted, for use in recover
 
-  // Simply never allow two retracts or recovers in a row
+  // Prevent two retracts or recovers in a row
   if (retracted[active_extruder] == retracting) return;
 
+  // Prevent two swap-retract or recovers in a row
   #if EXTRUDERS > 1
+    // Allow G10 S1 only after G10
+    if (swapping && retracted_swap[active_extruder] == retracting) return;
+    // G11 priority to recover the long retract if activated
     if (!retracting) swapping = retracted_swap[active_extruder];
   #else
     const bool swapping = false;
   //*/
 
   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 = planner.flow_percentage[active_extruder];
-
-  // Don't apply flow multiplication to retract/recover
-  planner.flow_percentage[active_extruder] = 100;
 
   // The current position will be the destination for E and Z moves
   set_destination_from_current();
-
   stepper.synchronize();  // Wait for buffered moves to complete
 
-  if (retracting) {
-    // Remember the Z height since G-code may include its own Z-hop
-    // For best results turn off Z hop if G-code already includes it
-    hop_height = destination[Z_AXIS];
+  const float renormalize = 100.0 / planner.flow_percentage[active_extruder] / planner.volumetric_multiplier[active_extruder];
 
+  if (retracting) {
     // Retract by moving from a faux E position back to the current E position
     feedrate_mm_s = retract_feedrate_mm_s;
-    current_position[E_AXIS] += (swapping ? swap_retract_length : retract_length) / planner.volumetric_multiplier[active_extruder];
+    current_position[E_AXIS] += (swapping ? swap_retract_length : retract_length) * renormalize;
     sync_plan_position_e();
     prepare_move_to_destination();
 
     // Is a Z hop set, and has the hop not yet been done?
-    if (has_zhop) {
-      hop_amount += retract_zlift;                // Carriage is raised for retraction hop
-      current_position[Z_AXIS] -= retract_zlift;  // Pretend current pos is lower. Next move raises Z.
-      SYNC_PLAN_POSITION_KINEMATIC();             // Set the planner to the new position
-      prepare_move_to_destination();              // Raise up to the old current pos
+    // No double zlifting
+    // Feedrate to the max
+    if (has_zhop && !hop_amount) {
+      hop_amount += retract_zlift;                        // Carriage is raised for retraction hop
+      feedrate_mm_s = planner.max_feedrate_mm_s[Z_AXIS];  // Z feedrate to max
+      current_position[Z_AXIS] -= retract_zlift;          // Pretend current pos is lower. Next move raises Z.
+      SYNC_PLAN_POSITION_KINEMATIC();                     // Set the planner to the new position
+      prepare_move_to_destination();                      // Raise up to the old current pos
     }
   }
   else {
     // If a hop was done and Z hasn't changed, undo the Z hop
-    if (hop_amount && NEAR(hop_height, destination[Z_AXIS])) {
-      current_position[Z_AXIS] += hop_amount;     // Pretend current pos is higher. Next move lowers Z.
-      SYNC_PLAN_POSITION_KINEMATIC();             // Set the planner to the new position
-      prepare_move_to_destination();              // Lower to the old current pos
-      hop_amount = 0.0;
+    if (hop_amount) {
+      current_position[Z_AXIS] -= retract_zlift;          // Pretend current pos is lower. Next move raises Z.
+      SYNC_PLAN_POSITION_KINEMATIC();                     // Set the planner to the new position
+      feedrate_mm_s = planner.max_feedrate_mm_s[Z_AXIS];  // Z feedrate to max
+      prepare_move_to_destination();                      // Raise up to the old current pos
+      hop_amount = 0.0;                                   // Clear hop
     }
 
     // A retract multiplier has been added here to get faster swap recovery
     feedrate_mm_s = swapping ? swap_retract_recover_feedrate_mm_s : retract_recover_feedrate_mm_s;
 
     const float move_e = swapping ? swap_retract_length + swap_retract_recover_length : retract_length + retract_recover_length;
-    current_position[E_AXIS] -= move_e / planner.volumetric_multiplier[active_extruder];
+    current_position[E_AXIS] -= move_e * renormalize;
     sync_plan_position_e();
-
     prepare_move_to_destination();  // Recover E
   }
 
-  // Restore flow and feedrate
-  planner.flow_percentage[active_extruder] = old_flow;
-  feedrate_mm_s = old_feedrate_mm_s;
+  feedrate_mm_s = old_feedrate_mm_s;                      // Restore original feedrate
 
-  // The active extruder is now retracted or recovered
-  retracted[active_extruder] = retracting;
+  retracted[active_extruder] = retracting;                // Active extruder now retracted / recovered
 
-  // If swap retract/recover then update the retracted_swap flag too
+  // If swap retract/recover update the retracted_swap flag too
   #if EXTRUDERS > 1
     if (swapping) retracted_swap[active_extruder] = retracting;
   #endif
     SERIAL_ECHOLNPAIR("hop_amount ", hop_amount);
   //*/
 
-} // retract()
+}
 
 #endif // FWRETRACT

Marlin/src/lcd/language/language_en.h

   #define MSG_CONTROL_RETRACT_RECOVER_SWAP    _UxGT("S UnRet mm")
 #endif
 #ifndef MSG_CONTROL_RETRACT_RECOVERF
-  #define MSG_CONTROL_RETRACT_RECOVERF        _UxGT("UnRet  V")
+  #define MSG_CONTROL_RETRACT_RECOVERF        _UxGT("UnRet V")
+#endif
+#ifndef MSG_CONTROL_RETRACT_RECOVER_SWAPF
+  #define MSG_CONTROL_RETRACT_RECOVER_SWAPF   _UxGT("S UnRet V")
 #endif
 #ifndef MSG_AUTORETRACT
   #define MSG_AUTORETRACT                     _UxGT("AutoRetr.")

Marlin/src/lcd/language/language_fr.h

 #define MSG_CONTROL_RETRACT_RECOVER         _UxGT("UnRet mm")
 #define MSG_CONTROL_RETRACT_RECOVER_SWAP    _UxGT("Ech. UnRet mm")
 #define MSG_CONTROL_RETRACT_RECOVERF        _UxGT("UnRet V")
+#define MSG_CONTROL_RETRACT_RECOVER_SWAPF   _UxGT("Ech. Retr. V")
 #define MSG_AUTORETRACT                     _UxGT("Retract. Auto.")
 #define MSG_FILAMENTCHANGE                  _UxGT("Changer filament")
 #define MSG_INIT_SDCARD                     _UxGT("Init. la carte SD")

Marlin/src/lcd/ultralcd.cpp

         MENU_ITEM_EDIT(float52, MSG_CONTROL_RETRACT_RECOVER_SWAP, &fwretract.swap_retract_recover_length, -100, 100);
       #endif
       MENU_ITEM_EDIT(float3, MSG_CONTROL_RETRACT_RECOVERF, &fwretract.retract_recover_feedrate_mm_s, 1, 999);
+      #if EXTRUDERS > 1
+        MENU_ITEM_EDIT(float3, MSG_CONTROL_RETRACT_RECOVER_SWAPF, &fwretract.swap_retract_recover_feedrate_mm_s, 1, 999);
+      #endif
       END_MENU();
     }