⚡️ G30 optimize and comment

Author: thinkyhead

Marlin/src/gcode/probe/G30.cpp

@@ -50,8 +50,7 @@
  */
 void GcodeSuite::G30() {
 
-  xy_pos_t old_pos = current_position,
-           probepos = current_position;
+  xy_pos_t probepos = current_position;
 
   const bool seenX = parser.seenval('X');
   if (seenX) probepos.x = RAW_X_POSITION(parser.value_linear_units());
@@ -62,21 +61,28 @@ void GcodeSuite::G30() {
 
   if (probe.can_reach(probepos)) {
 
-    if (seenX) old_pos.x = probepos.x;
-    if (seenY) old_pos.y = probepos.y;
-
     // Disable leveling so the planner won't mess with us
     TERN_(HAS_LEVELING, set_bed_leveling_enabled(false));
 
+    // Disable feedrate scaling so movement speeds are correct
     remember_feedrate_scaling_off();
 
+    // With VERBOSE_SINGLE_PROBE home only if needed
     TERN_(VERBOSE_SINGLE_PROBE, process_subcommands_now(F("G28O")));
 
+    // Raise after based on the 'E' parameter
     const ProbePtRaise raise_after = parser.boolval('E', true) ? PROBE_PT_STOW : PROBE_PT_NONE;
 
+    // Use 'C' to set Probe Temperature Compensation ON/OFF (on by default)
     TERN_(HAS_PTC, ptc.set_enabled(parser.boolval('C', true)));
+
+    // Probe the bed, optionally raise, and return the measured height
     const float measured_z = probe.probe_at_point(probepos, raise_after);
+
+    // After probing always re-enable Probe Temperature Compensation
     TERN_(HAS_PTC, ptc.set_enabled(true));
+
+    // Report a good probe result to the host and LCD
     if (!isnan(measured_z)) {
       const xy_pos_t lpos = probepos.asLogical();
       SString<30> msg(
@@ -88,9 +94,11 @@ void GcodeSuite::G30() {
       TERN_(VERBOSE_SINGLE_PROBE, ui.set_status(msg));
     }
 
+    // Restore feedrate scaling
     restore_feedrate_and_scaling();
 
-    do_blocking_move_to(old_pos);
+    // Move the nozzle to the position of the probe
+    do_blocking_move_to(probepos);
 
     if (raise_after == PROBE_PT_STOW)
       probe.move_z_after_probing();