Possible implementation. Needs tests.

farmbot_core/lib/farmbot_core/asset/point.ex

@@ -24,6 +24,7 @@ defmodule FarmbotCore.Asset.Point do
     field(:z, :float)
     field(:tool_id, :integer)
     field(:discarded_at, :utc_datetime)
+    field(:gantry_mounted, :boolean, default: false)
     field(:monitor, :boolean, default: true)
     timestamps()
   end

farmbot_core/priv/asset/migrations/20200219001135_add_gantry_mounted_fields.exs

@@ -0,0 +1,14 @@
+defmodule FarmbotCore.Asset.Repo.Migrations.AddGantryMountedFields do
+  use Ecto.Migration
+
+  def change do
+    alter table(:points) do
+      add(:gantry_mounted, :boolean, default: false)
+    end
+
+    # Invalidate cache of local device resource:
+    execute("UPDATE points SET updated_at = \"1970-11-07 16:52:31.618000\"")
+  end
+end
+# farmbot_core/priv/asset/migrations/20190926161914_add_point_discarded_at.exs
+# farmbot_core/priv/repo/migrations/20200219001135_add_gantry_mounted_fields.exs

farmbot_os/lib/farmbot_os/sys_calls/point_lookup.ex

@@ -2,6 +2,8 @@ defmodule FarmbotOS.SysCalls.PointLookup do
   @moduledoc false
 
   alias FarmbotCore.Asset
+  alias FarmbotOS.SysCalls.Movement
+
   require Logger
 
   def point(kind, id) do
@@ -11,15 +13,6 @@ defmodule FarmbotOS.SysCalls.PointLookup do
     end
   end
 
-  def get_toolslot_for_tool(id) do
-    with %{id: ^id} <- Asset.get_tool(id: id),
-         %{name: name, x: x, y: y, z: z} <- Asset.get_point(tool_id: id) do
-      %{name: name, x: x, y: y, z: z}
-    else
-      nil -> {:error, "Could not find point for tool by id: #{id}"}
-    end
-  end
-
   def get_point_group(id) when is_number(id) do
     case Asset.get_point_group(id: id) do
       nil -> {:error, "Could not find PointGroup.#{id}"}
@@ -35,4 +28,28 @@ defmodule FarmbotOS.SysCalls.PointLookup do
       %{id: id}, acc -> %{acc | point_ids: [id | acc.point_ids]}
     end)
   end
+
+  def get_toolslot_for_tool(id) do
+    tool = Asset.get_tool(id: id)
+    p = Asset.get_point(tool_id: id)
+
+    with %{id: ^id} <- tool,
+         %{name: name, x: x, y: y, z: z, gantry_mounted: mounted} <- p do
+      maybe_adjust_coordinates(%{
+        name: name,
+        x: x,
+        y: y,
+        z: z,
+        gantry_mounted: mounted
+      })
+    else
+      nil -> {:error, "Could not find point for tool by id: #{id}"}
+    end
+  end
+
+  defp maybe_adjust_coordinates(%{gantry_mounted: true} = point) do
+    %{point | x: Movement.get_current_x()}
+  end
+
+  defp maybe_adjust_coordinates(point), do: point
 end

farmbot_os/test/farmbot_os/syscalls/point_lookup_test.exs

@@ -39,13 +39,15 @@ defmodule FarmbotOS.SysCalls.PointLookupTest do
 
   test "PointLookup.get_toolslot_for_tool/1" do
     Repo.delete_all(Point)
+    Repo.delete_all(Tool)
     t = tool(%{name: "moisture probe"})
 
     important_part = %{
       name: "Tool Slot",
       x: 1.9,
       y: 2.9,
-      z: 3.9
+      z: 3.9,
+      gantry_mounted: false
     }
 
     other_stuff = %{