Fix bilinear ABL grid_start probe/nozzle coordinate mixup

Marlin/src/gcode/bedlevel/M420.cpp

@@ -68,14 +68,16 @@ void GcodeSuite::M420() {
 
   #if ENABLED(MARLIN_DEV_MODE)
     if (parser.intval('S') == 2) {
+      // Farthest XY coordinates that the probe can reach
       const float x_min = probe.min_x(), x_max = probe.max_x(),
                   y_min = probe.min_y(), y_max = probe.max_y();
       #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
         xy_pos_t start, spacing;
         start.set(x_min, y_min);
         spacing.set((x_max - x_min) / (GRID_MAX_CELLS_X),
                     (y_max - y_min) / (GRID_MAX_CELLS_Y));
-        bedlevel.set_grid(spacing, start);
+        // Shift the grid bounds by the probe offset because...?
+        bedlevel.set_grid(spacing, Probe::tool_xy_for_probe_xy(start));
       #endif
       GRID_LOOP(x, y) {
         bedlevel.z_values[x][y] = 0.001 * random(-200, 200);

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

@@ -521,7 +521,9 @@ G29_TYPE GcodeSuite::G29() {
     #endif
 
     #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
-      if (!abl.dryrun && (abl.gridSpacing != bedlevel.grid_spacing || abl.probe_position_lf != bedlevel.grid_start)) {
+      // Convert the probe-space grid origin to the motion/nozzle coordinate
+      const xy_pos_t grid_start = Probe::tool_xy_for_probe_xy(abl.probe_position_lf);
+      if (!abl.dryrun && (abl.gridSpacing != bedlevel.grid_spacing || grid_start != bedlevel.grid_start)) {
         reset_bed_level();      // Reset grid to 0.0 or "not probed". (Also disables ABL)
         abl.reenable = false;   // Can't re-enable (on error) until the new grid is written
       }
@@ -880,7 +882,7 @@ G29_TYPE GcodeSuite::G29() {
       if (abl.dryrun)
         bedlevel.print_leveling_grid(&abl.z_values);
       else {
-        bedlevel.set_grid(abl.gridSpacing, abl.probe_position_lf);
+        bedlevel.set_grid(abl.gridSpacing, Probe::tool_xy_for_probe_xy(abl.probe_position_lf));
         COPY(bedlevel.z_values, abl.z_values);
         TERN_(IS_KINEMATIC, bedlevel.extrapolate_unprobed_bed_level());
         bedlevel.refresh_bed_level();

Marlin/src/module/probe.h

@@ -244,6 +244,18 @@ class Probe {
     static constexpr xy_pos_t offset_xy = xy_pos_t({ 0, 0 });   // See #16767
   #endif
 
+  // Input: A coordinate destination for the probe.
+  // Return: The tool position that will put the probe there.
+  // Also adjusted for the tool offset unless PROBING_TOOL is used.
+  // With PROBING_TOOL the probe offsets are presumed relative to that tool, not T0.
+  static xy_pos_t tool_xy_for_probe_xy(const xy_pos_t &probe_xy) {
+    xy_pos_t nozPos = DIFF_TERN(HAS_PROBE_XY_OFFSET, probe_xy, offset_xy);
+    #if DISABLED(DO_TOOLCHANGE_FOR_PROBING)
+      nozPos += xy_pos_t(motion.active_hotend_offset());
+    #endif
+    return nozPos;
+  }
+
   static bool deploy(const bool no_return=false) { return set_deployed(true, no_return); }
   static bool stow(const bool no_return=false)   { return set_deployed(false, no_return); }
 

Marlin/src/module/settings.cpp

@@ -3190,7 +3190,7 @@ void MarlinSettings::postprocess() {
     #define MESH_STORE_SIZE sizeof(TERN(OPTIMIZED_MESH_STORAGE, mesh_store_t, bedlevel.z_values))
 
     uint16_t MarlinSettings::calc_num_meshes() {
-      return MIN(MAX_SAVED_MESHES, (meshes_end - meshes_start_index()) / MESH_STORE_SIZE);
+      return _MIN(MAX_SAVED_MESHES, (meshes_end - meshes_start_index()) / MESH_STORE_SIZE);
     }
 
     int MarlinSettings::mesh_slot_offset(const int8_t slot) {