Fix cold/lengthy extrusion handling

Marlin/Marlin_main.cpp

  *
  * This may result in several calls to planner.buffer_line to
  * do smaller moves for DELTA, SCARA, mesh moves, etc.
+ *
+ * Make sure current_position[E] and destination[E] are good
+ * before calling or cold/lengthy extrusion may get missed.
  */
 void prepare_move_to_destination() {
   clamp_to_software_endstops(destination);
   refresh_cmd_timeout();
 
-  #if ENABLED(PREVENT_COLD_EXTRUSION)
+  #if ENABLED(PREVENT_COLD_EXTRUSION) || ENABLED(PREVENT_LENGTHY_EXTRUDE)
 
     if (!DEBUGGING(DRYRUN)) {
       if (destination[E_AXIS] != current_position[E_AXIS]) {
-        if (thermalManager.tooColdToExtrude(active_extruder)) {
-          current_position[E_AXIS] = destination[E_AXIS]; // Behave as if the move really took place, but ignore E part
-          SERIAL_ECHO_START();
-          SERIAL_ECHOLNPGM(MSG_ERR_COLD_EXTRUDE_STOP);
-        }
+        #if ENABLED(PREVENT_COLD_EXTRUSION)
+          if (thermalManager.tooColdToExtrude(active_extruder)) {
+            current_position[E_AXIS] = destination[E_AXIS]; // Behave as if the move really took place, but ignore E part
+            SERIAL_ECHO_START();
+            SERIAL_ECHOLNPGM(MSG_ERR_COLD_EXTRUDE_STOP);
+          }
+        #endif // PREVENT_COLD_EXTRUSION
         #if ENABLED(PREVENT_LENGTHY_EXTRUDE)
-          if (fabs(destination[E_AXIS] - current_position[E_AXIS]) > EXTRUDE_MAXLENGTH / volumetric_multiplier[active_extruder]) {
+          if (FABS(destination[E_AXIS] - current_position[E_AXIS]) > (EXTRUDE_MAXLENGTH) / volumetric_multiplier[active_extruder]) {
             current_position[E_AXIS] = destination[E_AXIS]; // Behave as if the move really took place, but ignore E part
             SERIAL_ECHO_START();
             SERIAL_ECHOLNPGM(MSG_ERR_LONG_EXTRUDE_STOP);
           }
-        #endif
+        #endif // PREVENT_LENGTHY_EXTRUDE
       }
     }
 

Marlin/planner.cpp

 
   long de = target[E_AXIS] - position[E_AXIS];
 
+  const float e_factor = volumetric_multiplier[extruder] * flow_percentage[extruder] * 0.01;
+
   #if ENABLED(LIN_ADVANCE)
     float de_float = e - position_float[E_AXIS];
   #endif
 
-  #if ENABLED(PREVENT_COLD_EXTRUSION)
+  #if ENABLED(PREVENT_COLD_EXTRUSION) || ENABLED(PREVENT_LENGTHY_EXTRUDE)
     if (de) {
-      if (thermalManager.tooColdToExtrude(extruder)) {
-        position[E_AXIS] = target[E_AXIS]; // Behave as if the move really took place, but ignore E part
-        de = 0; // no difference
-        #if ENABLED(LIN_ADVANCE)
-          position_float[E_AXIS] = e;
-          de_float = 0;
-        #endif
-        SERIAL_ECHO_START();
-        SERIAL_ECHOLNPGM(MSG_ERR_COLD_EXTRUDE_STOP);
-      }
+      #if ENABLED(PREVENT_COLD_EXTRUSION)
+        if (thermalManager.tooColdToExtrude(extruder)) {
+          position[E_AXIS] = target[E_AXIS]; // Behave as if the move really took place, but ignore E part
+          de = 0; // no difference
+          #if ENABLED(LIN_ADVANCE)
+            position_float[E_AXIS] = e;
+            de_float = 0;
+          #endif
+          SERIAL_ECHO_START();
+          SERIAL_ECHOLNPGM(MSG_ERR_COLD_EXTRUDE_STOP);
+        }
+      #endif // PREVENT_COLD_EXTRUSION
       #if ENABLED(PREVENT_LENGTHY_EXTRUDE)
-        int32_t de_mm = labs(de * volumetric_multiplier[active_extruder]);
+        const int32_t de_mm = labs(de * e_factor);
         if (de_mm > (int32_t)axis_steps_per_mm[E_AXIS_N] * (EXTRUDE_MAXLENGTH)) { // It's not important to get max. extrusion length in a precision < 1mm, so save some cycles and cast to int
           position[E_AXIS] = target[E_AXIS]; // Behave as if the move really took place, but ignore E part
           de = 0; // no difference
           SERIAL_ECHO_START();
           SERIAL_ECHOLNPGM(MSG_ERR_LONG_EXTRUDE_STOP);
         }
-      #endif
+      #endif // PREVENT_LENGTHY_EXTRUDE
     }
-  #endif
+  #endif // PREVENT_COLD_EXTRUSION || PREVENT_LENGTHY_EXTRUDE
 
   // Compute direction bit-mask for this block
   uint8_t dm = 0;
   #endif
   if (de < 0) SBI(dm, E_AXIS);
 
-  const float esteps_float = de * volumetric_multiplier[extruder] * flow_percentage[extruder] * 0.01;
+  const float esteps_float = de * e_factor;
   const int32_t esteps = abs(esteps_float) + 0.5;
 
   // Calculate the buffer head after we push this byte