Restore extruder_offset, init more simply

Marlin/Configuration.h

 // This defines the number of extruders
 #define EXTRUDERS 1
 
+// Offset of the extruders (uncomment if using more than one and relying on firmware to position when changing).
+// The offset has to be X=0, Y=0 for the extruder 0 hotend (default extruder).
+// For the other hotends it is their distance from the extruder 0 hotend.
+#define EXTRUDER_OFFSET_X {0.0, 20.00} // (in mm) for each extruder, offset of the hotend on the X axis
+#define EXTRUDER_OFFSET_Y {0.0, 5.00}  // (in mm) for each extruder, offset of the hotend on the Y axis
+
 //// The following define selects which power supply you have. Please choose the one that matches your setup
 // 1 = ATX
 // 2 = X-Box 360 203Watts (the blue wire connected to PS_ON and the red wire to VCC)
 #define DEFAULT_RETRACT_ACCELERATION  3000   // E acceleration in mm/s^2 for retracts
 #define DEFAULT_TRAVEL_ACCELERATION   3000    // X, Y, Z acceleration in mm/s^2 for travel (non printing) moves
 
-// Offset of the extruders (uncomment if using more than one and relying on firmware to position when changing).
-// The offset has to be X=0, Y=0 for the extruder 0 hotend (default extruder).
-// For the other hotends it is their distance from the extruder 0 hotend.
-// #define EXTRUDER_OFFSET_X {0.0, 20.00} // (in mm) for each extruder, offset of the hotend on the X axis
-// #define EXTRUDER_OFFSET_Y {0.0, 5.00}  // (in mm) for each extruder, offset of the hotend on the Y axis
-
 // The speed change that does not require acceleration (i.e. the software might assume it can be done instantaneously)
 #define DEFAULT_XYJERK                20.0    // (mm/sec)
 #define DEFAULT_ZJERK                 0.4     // (mm/sec)

Marlin/Marlin_main.cpp

 float max_pos[3] = { X_MAX_POS, Y_MAX_POS, Z_MAX_POS };
 bool axis_known_position[3] = { false };
 
-// Extruder offset
+// Extruder offsets
 #if EXTRUDERS > 1
   #ifndef EXTRUDER_OFFSET_X
     #define EXTRUDER_OFFSET_X { 0 }
   #ifndef EXTRUDER_OFFSET_Y
     #define EXTRUDER_OFFSET_Y { 0 }
   #endif
-  #ifndef DUAL_X_CARRIAGE
-    #define NUM_EXTRUDER_OFFSETS 2 // only in XY plane
-  #else
-    #define NUM_EXTRUDER_OFFSETS 3 // supports offsets in XYZ plane
-  #endif
-  float extruder_offset[EXTRUDERS][NUM_EXTRUDER_OFFSETS];
+  float extruder_offset[][EXTRUDERS] = {
+    EXTRUDER_OFFSET_X,
+    EXTRUDER_OFFSET_Y
+    #ifdef DUAL_X_CARRIAGE
+      , { 0 } // supports offsets in XYZ plane
+    #endif
+  };
 #endif
 
 uint8_t active_extruder = 0;
 
 void setup()
 {
-  #if EXTRUDERS > 1
-    float offset[3][EXTRUDERS] = { EXTRUDER_OFFSET_X, EXTRUDER_OFFSET_Y, ARRAY_BY_EXTRUDERS(0,0,0,0) };
-    for (int e=0; e<EXTRUDERS; e++)
-      for (int i=0; i<NUM_EXTRUDER_OFFSETS; i++)
-        extruder_offset[e][i] = offset[i][e];
-  #endif
-
   setup_killpin();
   setup_filrunoutpin();
   setup_powerhold();
       // second X-carriage offset when homed - otherwise X2_HOME_POS is used.
       // This allow soft recalibration of the second extruder offset position without firmware reflash
       // (through the M218 command).
-      return (extruder_offset[1][X_AXIS] > 0) ? extruder_offset[1][X_AXIS] : X2_HOME_POS;
+      return (extruder_offset[X_AXIS][1] > 0) ? extruder_offset[X_AXIS][1] : X2_HOME_POS;
   }
 
   static int x_home_dir(int extruder) {
       if (active_extruder != 0) {
         current_position[X_AXIS] = x_home_pos(active_extruder);
                  min_pos[X_AXIS] = X2_MIN_POS;
-                 max_pos[X_AXIS] = max(extruder_offset[1][X_AXIS], X2_MAX_POS);
+                 max_pos[X_AXIS] = max(extruder_offset[X_AXIS][1], X2_MAX_POS);
         return;
       }
       else if (dual_x_carriage_mode == DXC_DUPLICATION_MODE) {
         float xoff = home_offset[X_AXIS];
         current_position[X_AXIS] = base_home_pos(X_AXIS) + xoff;
                  min_pos[X_AXIS] = base_min_pos(X_AXIS) + xoff;
-                 max_pos[X_AXIS] = min(base_max_pos(X_AXIS) + xoff, max(extruder_offset[1][X_AXIS], X2_MAX_POS) - duplicate_extruder_x_offset);
+                 max_pos[X_AXIS] = min(base_max_pos(X_AXIS) + xoff, max(extruder_offset[X_AXIS][1], X2_MAX_POS) - duplicate_extruder_x_offset);
         return;
       }
     }
   inline void gcode_M218() {
     if (setTargetedHotend(218)) return;
 
-    if (code_seen('X')) extruder_offset[tmp_extruder][X_AXIS] = code_value();
-    if (code_seen('Y')) extruder_offset[tmp_extruder][Y_AXIS] = code_value();
+    if (code_seen('X')) extruder_offset[X_AXIS][tmp_extruder] = code_value();
+    if (code_seen('Y')) extruder_offset[Y_AXIS][tmp_extruder] = code_value();
 
     #ifdef DUAL_X_CARRIAGE
-      if (code_seen('Z')) extruder_offset[tmp_extruder][Z_AXIS] = code_value();
+      if (code_seen('Z')) extruder_offset[Z_AXIS][tmp_extruder] = code_value();
     #endif
 
     SERIAL_ECHO_START;
     SERIAL_ECHOPGM(MSG_HOTEND_OFFSET);
     for (tmp_extruder = 0; tmp_extruder < EXTRUDERS; tmp_extruder++) {
       SERIAL_ECHO(" ");
-      SERIAL_ECHO(extruder_offset[tmp_extruder][X_AXIS]);
+      SERIAL_ECHO(extruder_offset[X_AXIS][tmp_extruder]);
       SERIAL_ECHO(",");
-      SERIAL_ECHO(extruder_offset[tmp_extruder][Y_AXIS]);
+      SERIAL_ECHO(extruder_offset[Y_AXIS][tmp_extruder]);
       #ifdef DUAL_X_CARRIAGE
         SERIAL_ECHO(",");
-        SERIAL_ECHO(extruder_offset[tmp_extruder][Z_AXIS]);
+        SERIAL_ECHO(extruder_offset[Z_AXIS][tmp_extruder]);
       #endif
     }
     SERIAL_EOL;
         SERIAL_ECHO_START;
         SERIAL_ECHOPGM(MSG_HOTEND_OFFSET);
         SERIAL_ECHO(" ");
-        SERIAL_ECHO(extruder_offset[0][X_AXIS]);
+        SERIAL_ECHO(extruder_offset[X_AXIS][0]);
         SERIAL_ECHO(",");
-        SERIAL_ECHO(extruder_offset[0][Y_AXIS]);
+        SERIAL_ECHO(extruder_offset[Y_AXIS][0]);
         SERIAL_ECHO(" ");
         SERIAL_ECHO(duplicate_extruder_x_offset);
         SERIAL_ECHO(",");
-        SERIAL_ECHOLN(extruder_offset[1][Y_AXIS]);
+        SERIAL_ECHOLN(extruder_offset[Y_AXIS][1]);
         break;
       case DXC_FULL_CONTROL_MODE:
       case DXC_AUTO_PARK_MODE:
 
           // apply Y & Z extruder offset (x offset is already used in determining home pos)
           current_position[Y_AXIS] = current_position[Y_AXIS] -
-                       extruder_offset[active_extruder][Y_AXIS] +
-                       extruder_offset[tmp_extruder][Y_AXIS];
+                       extruder_offset[Y_AXIS][active_extruder] +
+                       extruder_offset[Y_AXIS][tmp_extruder];
           current_position[Z_AXIS] = current_position[Z_AXIS] -
-                       extruder_offset[active_extruder][Z_AXIS] +
-                       extruder_offset[tmp_extruder][Z_AXIS];
+                       extruder_offset[Z_AXIS][active_extruder] +
+                       extruder_offset[Z_AXIS][tmp_extruder];
 
           active_extruder = tmp_extruder;
 
         #else // !DUAL_X_CARRIAGE
           // Offset extruder (only by XY)
           for (int i=X_AXIS; i<=Y_AXIS; i++)
-            current_position[i] += extruder_offset[tmp_extruder][i] - extruder_offset[active_extruder][i];
+            current_position[i] += extruder_offset[i][tmp_extruder] - extruder_offset[i][active_extruder];
           // Set the new active extruder and position
           active_extruder = tmp_extruder;
         #endif // !DUAL_X_CARRIAGE