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Update documentation on accessing PVs in scripts #3648

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Update documentation on accessing PVs in scripts #3648

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19 changes: 15 additions & 4 deletions app/display/editor/doc/access_pv_in_script.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,17 @@ Access PV in Script
The input PVs for a script can be accessed in script via ``pvs`` object. The order of the input PVs in the
configuration list is preserved in ``pvs``. ``pvs[0]`` is the first input pv. If you have N input PVs, ``pvs[N-1]`` is the last input PV.

A button-type widget configured to execute script(s) should instead
reference pvs using ``widget.getPV()`` or ``widget.getPVByName(my_pv_name)``.
When using the ``pvs`` object, the display runtime will invoke the script once all PVs connected
and then whenever those marked as a "Trigger" change.
Scripts might also access PVs associated with a widget like this, but the preferred way
is using ``pvs`` for PVs listed as script inputs.

.. code-block:: python

from org.csstudio.display.builder.runtime.script import ScriptUtil
pv = ScriptUtil.getPrimaryPV(widget)
pvs = ScriptUtil.getPVs(widget)
pv = ScriptUtil.getPVByName(widget, "SomePVName")

You can read/write PV or get its timestamp or severity via the utility APIs provided in ``PVUtil``.

Expand All @@ -20,16 +29,18 @@ You can read/write PV or get its timestamp or severity via the utility APIs prov
.. code-block:: python

from org.csstudio.display.builder.runtime.script import PVUtil
value = PVUtil.getDouble(pvs[0]);
value = PVUtil.getDouble(pvs[0])

**Write PV Value**

While the ``pvs`` are configured as script inputs, they may also be used
as outputs by writing to them.
Several method argument types are supported, e.g. Double, Double[], Integer, String. If writing a PV is forbidden by
PV security, an exception will be thrown and shown in console.

.. code-block:: python

pvs[0].write(0);
pvs[0].write(0)

**Get severity of PV**

Expand Down