G12 defaults per tool. Event G-code for post-toolchange (#16554)

Marlin/Configuration.h

   // Default number of triangles
   #define NOZZLE_CLEAN_TRIANGLES  3
 
-  // Specify positions as { X, Y, Z }
-  #define NOZZLE_CLEAN_START_POINT {  30, 30, (Z_MIN_POS + 1) }
-  #define NOZZLE_CLEAN_END_POINT   { 100, 60, (Z_MIN_POS + 1) }
+  // Specify positions for each tool as { { X, Y, Z }, { X, Y, Z } }
+  // Dual hotend system may use { {  -20, (Y_BED_SIZE / 2), (Z_MIN_POS + 1) },  {  420, (Y_BED_SIZE / 2), (Z_MIN_POS + 1) }}
+  #define NOZZLE_CLEAN_START_POINT { {  30, 30, (Z_MIN_POS + 1) } }
+  #define NOZZLE_CLEAN_END_POINT   { { 100, 60, (Z_MIN_POS + 1) } }
 
   // Circular pattern radius
   #define NOZZLE_CLEAN_CIRCLE_RADIUS 6.5

Marlin/Configuration_adv.h

   // Z raise distance for tool-change, as needed for some extruders
   #define TOOLCHANGE_ZRAISE     2  // (mm)
   //#define TOOLCHANGE_NO_RETURN   // Never return to the previous position on tool-change
+  #if ENABLED(TOOLCHANGE_NO_RETURN)
+    //#define EVENT_GCODE_AFTER_TOOLCHANGE "G12X"   // G-code to run after tool-change is complete
+  #endif
 
   // Retract and prime filament on tool-change
   //#define TOOLCHANGE_FILAMENT_SWAP

Marlin/src/libs/nozzle.cpp

    * @param argument depends on the cleaning pattern
    */
   void Nozzle::clean(const uint8_t &pattern, const uint8_t &strokes, const float &radius, const uint8_t &objects, const uint8_t cleans) {
-    xyz_pos_t start = NOZZLE_CLEAN_START_POINT, end = NOZZLE_CLEAN_END_POINT;
+    xyz_pos_t start[HOTENDS] = NOZZLE_CLEAN_START_POINT, end[HOTENDS] = NOZZLE_CLEAN_END_POINT, middle[HOTENDS] = NOZZLE_CLEAN_CIRCLE_MIDDLE;
 
     if (pattern == 2) {
       if (!(cleans & (_BV(X_AXIS) | _BV(Y_AXIS)))) {
         SERIAL_ECHOLNPGM("Warning : Clean Circle requires XY");
         return;
       }
-      constexpr xyz_pos_t middle NOZZLE_CLEAN_CIRCLE_MIDDLE;
-      end = middle;
     }
     else {
-      if (!TEST(cleans, X_AXIS)) start.x = end.x = current_position.x;
-      if (!TEST(cleans, Y_AXIS)) start.y = end.y = current_position.y;
+      if (!TEST(cleans, X_AXIS)) start[active_extruder].x = end[active_extruder].x = current_position.x;
+      if (!TEST(cleans, Y_AXIS)) start[active_extruder].y = end[active_extruder].y = current_position.y;
     }
-    if (!TEST(cleans, Z_AXIS)) start.z = end.z = current_position.z;
+    if (!TEST(cleans, Z_AXIS)) start[active_extruder].z = end[active_extruder].z = current_position.z;
 
     switch (pattern) {
-       case 1: zigzag(start, end, strokes, objects); break;
-       case 2: circle(start, end, strokes, radius);  break;
-      default: stroke(start, end, strokes);
+       case 1: zigzag(start[active_extruder], end[active_extruder], strokes, objects); break;
+       case 2: circle(start[active_extruder], middle[active_extruder], strokes, radius);  break;
+      default: stroke(start[active_extruder], end[active_extruder], strokes);
     }
   }
 

Marlin/src/module/tool_change.cpp

       fanmux_switch(active_extruder);
     #endif
 
+    #ifdef EVENT_GCODE_AFTER_TOOLCHANGE
+      gcode.process_subcommands_now_P(EVENT_GCODE_AFTER_TOOLCHANGE);
+    #endif
+
     SERIAL_ECHO_START();
     SERIAL_ECHOLNPAIR(MSG_ACTIVE_EXTRUDER, int(active_extruder));