Debug of G2-G3 for UBL (#12386)

Changes only affect UBL.  Everything else is left alone.

Marlin/src/gcode/bedlevel/G26.cpp

 
   if (z != last_z) {
     last_z = z;
-    feed_value = planner.settings.max_feedrate_mm_s[Z_AXIS]/(3.0);  // Base the feed rate off of the configured Z_AXIS feed rate
+    feed_value = planner.settings.max_feedrate_mm_s[Z_AXIS]/(2.0);  // Base the feed rate off of the configured Z_AXIS feed rate
 
     destination[X_AXIS] = current_position[X_AXIS];
     destination[Y_AXIS] = current_position[Y_AXIS];
-    destination[Z_AXIS] = z;                          // We know the last_z==z or we wouldn't be in this block of code.
+    destination[Z_AXIS] = z;                          // We know the last_z!=z or we wouldn't be in this block of code.
     destination[E_AXIS] = current_position[E_AXIS];
 
     G26_line_to_destination(feed_value);
 
   // Check if X or Y is involved in the movement.
   // Yes: a 'normal' movement. No: a retract() or recover()
-  feed_value = has_xy_component ? PLANNER_XY_FEEDRATE() / 10.0 : planner.settings.max_feedrate_mm_s[E_AXIS] / 1.5;
+  feed_value = has_xy_component ? PLANNER_XY_FEEDRATE() / 3.0 : planner.settings.max_feedrate_mm_s[E_AXIS] / 1.5;
 
   if (g26_debug_flag) SERIAL_ECHOLNPAIR("in move_to() feed_value for XY:", feed_value);
 
         recover_filament(destination);
         const float save_feedrate = feedrate_mm_s;
         feedrate_mm_s = PLANNER_XY_FEEDRATE() / 10.0;
+
+        if (g26_debug_flag) {
+          SERIAL_ECHOPAIR(" plan_arc(ex=", endpoint[X_AXIS]);
+          SERIAL_ECHOPAIR(", ey=", endpoint[Y_AXIS]);
+          SERIAL_ECHOPAIR(", ez=", endpoint[Z_AXIS]);
+          SERIAL_ECHOPAIR(", len=", arc_offset);
+          SERIAL_ECHOPAIR(") -> (ex=", current_position[X_AXIS]);
+          SERIAL_ECHOPAIR(", ey=", current_position[Y_AXIS]);
+          SERIAL_ECHOPAIR(", ez=", current_position[Z_AXIS]);
+          SERIAL_CHAR(')');
+          SERIAL_EOL();
+        }
+
         plan_arc(endpoint, arc_offset, false);  // Draw a counter-clockwise arc
         feedrate_mm_s = save_feedrate;
         set_destination_from_current();

Marlin/src/gcode/motion/G2_G3.cpp

   float r_P = -offset[0], r_Q = -offset[1];
 
   const float radius = HYPOT(r_P, r_Q),
+              #if ENABLED(AUTO_BED_LEVELING_UBL)
+                start_L  = current_position[l_axis],
+              #endif
               center_P = current_position[p_axis] - r_P,
               center_Q = current_position[q_axis] - r_Q,
               rt_X = cart[p_axis] - center_P,
     // Update raw location
     raw[p_axis] = center_P + r_P;
     raw[q_axis] = center_Q + r_Q;
-    raw[l_axis] += linear_per_segment;
+    #if ENABLED(AUTO_BED_LEVELING_UBL)
+      raw[l_axis] = start_L;
+    #else
+      raw[l_axis] += linear_per_segment;
+    #endif
     raw[E_AXIS] += extruder_per_segment;
 
     clamp_to_software_endstops(raw);
 
   // Ensure last segment arrives at target location.
   COPY(raw, cart);
+  #if ENABLED(AUTO_BED_LEVELING_UBL)
+    raw[l_axis] = start_L;
+  #endif
 
   #if HAS_LEVELING && !PLANNER_LEVELING
     planner.apply_leveling(raw);
     #endif
   );
 
+  #if ENABLED(AUTO_BED_LEVELING_UBL)
+    raw[l_axis] = start_L;
+  #endif
   COPY(current_position, raw);
 } // plan_arc