Sync and report changed position

Marlin/src/feature/bedlevel/bedlevel.cpp

@@ -128,13 +128,17 @@ void set_bed_leveling_enabled(const bool enable/*=true*/) {
         // so compensation will give the right stepper counts.
         planner.unapply_leveling(current_position);
 
+      SYNC_PLAN_POSITION_KINEMATIC();
+
     #endif // OLDSCHOOL_ABL
   }
 }
 
 #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
 
-  void set_z_fade_height(const float zfh) {
+  void set_z_fade_height(const float zfh, const bool do_report/*=true*/) {
+
+    if (planner.z_fade_height == zfh) return; // do nothing if no change
 
     const bool level_active = planner.leveling_active;
 
@@ -145,6 +149,10 @@ void set_bed_leveling_enabled(const bool enable/*=true*/) {
     planner.set_z_fade_height(zfh);
 
     if (level_active) {
+      const float oldpos[XYZE] = {
+        current_position[X_AXIS], current_position[Y_AXIS],
+        current_position[Z_AXIS], current_position[E_AXIS]
+      };
       #if ENABLED(AUTO_BED_LEVELING_UBL)
         set_bed_leveling_enabled(true);  // turn back on after changing fade height
       #else
@@ -155,7 +163,10 @@ void set_bed_leveling_enabled(const bool enable/*=true*/) {
             Z_AXIS
           #endif
         );
+        SYNC_PLAN_POSITION_KINEMATIC();
       #endif
+      if (do_report && memcmp(oldpos, current_position, sizeof(oldpos)))
+        report_current_position();
     }
   }
 

Marlin/src/feature/bedlevel/bedlevel.h

@@ -47,7 +47,7 @@ void set_bed_leveling_enabled(const bool enable=true);
 void reset_bed_level();
 
 #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
-  void set_z_fade_height(const float zfh);
+  void set_z_fade_height(const float zfh, const bool do_report=true);
 #endif
 
 #if ENABLED(AUTO_BED_LEVELING_BILINEAR) || ENABLED(MESH_BED_LEVELING)

Marlin/src/feature/bedlevel/ubl/ubl.cpp

@@ -71,17 +71,19 @@
   volatile int unified_bed_leveling::encoder_diff;
 
   unified_bed_leveling::unified_bed_leveling() {
-    ubl_cnt++;  // Debug counter to insure we only have one UBL object present in memory.  We can eliminate this (and all references to ubl_cnt) very soon.
+    ubl_cnt++;  // Debug counter to ensure we only have one UBL object present in memory.  We can eliminate this (and all references to ubl_cnt) very soon.
     reset();
   }
 
   void unified_bed_leveling::reset() {
+    const bool was_enabled = planner.leveling_active;
     set_bed_leveling_enabled(false);
     storage_slot = -1;
     #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
       planner.set_z_fade_height(10.0);
     #endif
     ZERO(z_values);
+    if (was_enabled) report_current_position();
   }
 
   void unified_bed_leveling::invalidate() {

Marlin/src/gcode/bedlevel/M420.cpp

@@ -108,7 +108,7 @@ void GcodeSuite::M420() {
   if (parser.seen('S')) set_bed_leveling_enabled(to_enable);
 
   #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
-    if (parser.seen('Z')) set_z_fade_height(parser.value_linear_units());
+    if (parser.seen('Z')) set_z_fade_height(parser.value_linear_units(), false);
   #endif
 
   const bool new_status = planner.leveling_active;

Marlin/src/gcode/bedlevel/abl/G29.cpp

@@ -285,6 +285,7 @@ void GcodeSuite::G29() {
             bed_level_virt_interpolate();
           #endif
           set_bed_leveling_enabled(abl_should_enable);
+          if (abl_should_enable) report_current_position();
         }
         return;
       } // parser.seen('W')

Marlin/src/module/motion.cpp

@@ -211,6 +211,12 @@ void get_cartesian_from_steppers() {
  * Set the current_position for an axis based on
  * the stepper positions, removing any leveling that
  * may have been applied.
+ *
+ * To prevent small shifts in axis position always call
+ * SYNC_PLAN_POSITION_KINEMATIC after updating axes with this.
+ *
+ * To keep hosts in sync, always call report_current_position
+ * after updating the current_position.
  */
 void set_current_from_steppers_for_axis(const AxisEnum axis) {
   get_cartesian_from_steppers();