.. _manual_enable_alter_motion:

enable_alter_motion (Manual Mode)
------------------------------------------
This section explains how to use :ref:`enable_alter_motion <enable_alter_motion>` during **Manual (Teach)** operations.  
It activates alter motion mode, which lets you apply small trajectory corrections while a task-space motion command (for example ``movel``) is running. Joint-space motions such as ``movej`` cannot be altered; ``alter_motion`` calls during them are refused.
This is especially useful for **fine-tuning approach paths**, adjusting tool orientation during contact,  
or visually correcting the TCP position under camera guidance.

**Typical usage**

- Enable before running a fine manual adjustment loop (using :ref:`alter_motion <manual_alter_motion>`).  
- Define movement limits for both **position** and **orientation** to ensure safe manual control.  
- Commonly used in precision teaching tasks such as welding start-point tuning or surface touch alignment.

.. Note::

    - Must be called in **user thread** before any alter commands.  
    - It remains active until disable_alter_motion is called or the robot enters EMERGENCY_STOP, SAFE_OFF or SAFE_OFF2; after that, call enable_alter_motion again after servo on.
    - The set limits prevent excessive tool displacement or orientation changes.

**Example: Enable Alter Motion with Safety Boundaries**

.. code-block:: cpp

   // Step 1: Ensure robot is connected and in Manual Mode
   // (Assume servo ON and safe workspace conditions)

   // Step 2: Define safety limits for manual correction
   float fLimitDpos[2]     = {5.0f, 3.0f};   // ±5 mm (position), ±3° (rotation)
   float fLimitDposPer[2]  = {-10000.f, -10000.f};  // no per-cycle limit

   // Step 3: Enable alter motion to allow micro path correction
   drfl.enable_alter_motion(5, PATH_MODE_DPOS, COORDINATE_SYSTEM_BASE,
                            fLimitDpos, fLimitDposPer);

   printf("Alter motion enabled. You can now apply small path adjustments.\n");

**Tips**

- Ideal to call just before visual or tactile alignment.  
- The accumulated amount or the increment amount is not limited if both elements of ``fLimitDpos`` or ``fLimitDposPer`` are ``-10000``.
- Once alignment is done, use :ref:`disable_alter_motion <manual_disable_alter_motion>` to finalize the pose.