From 5fd20ecac3725f84bf8f312479b7d1526a5b52d5 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Wed, 13 Apr 2016 02:33:22 -0700
Subject: [PATCH 1/2] Comments on some movement functions

---
 Marlin/Marlin_main.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index fa280bb86..cd41e50f1 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -1303,18 +1303,33 @@ inline void set_homing_bump_feedrate(AxisEnum axis) {
   }
   feedrate = homing_feedrate[axis] / hbd;
 }
+//
+// line_to_current_position
+// Move the planner to the current position from wherever it last moved
+// (or from wherever it has been told it is located).
+//
 inline void line_to_current_position() {
   plan_buffer_line(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS], feedrate / 60, active_extruder);
 }
 inline void line_to_z(float zPosition) {
   plan_buffer_line(current_position[X_AXIS], current_position[Y_AXIS], zPosition, current_position[E_AXIS], feedrate / 60, active_extruder);
 }
+//
+// line_to_destination
+// Move the planner, not necessarily synced with current_position
+//
 inline void line_to_destination(float mm_m) {
   plan_buffer_line(destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS], mm_m / 60, active_extruder);
 }
 inline void line_to_destination() {
   line_to_destination(feedrate);
 }
+/**
+ * sync_plan_position
+ * Set planner / stepper positions to the cartesian current_position.
+ * The stepper code translates these coordinates into step units.
+ * Allows translation between steps and units (mm) for cartesian & core robots
+ */
 inline void sync_plan_position() {
   #if ENABLED(DEBUG_LEVELING_FEATURE)
     if (DEBUGGING(LEVELING)) DEBUG_POS("sync_plan_position", current_position);

From cfcd3d7b3eb8ebf987b926f659450c104e4ca858 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Wed, 13 Apr 2016 02:33:53 -0700
Subject: [PATCH 2/2] Rename z_offset local to zoffset

---
 Marlin/Marlin_main.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index cd41e50f1..d169d3531 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -3131,8 +3131,8 @@ inline void gcode_G28() {
       #if ENABLED(DELTA)
         delta_grid_spacing[0] = xGridSpacing;
         delta_grid_spacing[1] = yGridSpacing;
-        float z_offset = zprobe_zoffset;
-        if (code_seen(axis_codes[Z_AXIS])) z_offset += code_value();
+        float zoffset = zprobe_zoffset;
+        if (code_seen(axis_codes[Z_AXIS])) zoffset += code_value();
       #else // !DELTA
         /**
          * solve the plane equation ax + by + d = z
@@ -3222,7 +3222,7 @@ inline void gcode_G28() {
             eqnAMatrix[probePointCounter + 2 * abl2] = 1;
             indexIntoAB[xCount][yCount] = probePointCounter;
           #else
-            bed_level[xCount][yCount] = measured_z + z_offset;
+            bed_level[xCount][yCount] = measured_z + zoffset;
           #endif
 
           probePointCounter++;