MQTT: (WIP) Fix OpenSSL linking.
Pages, Jumps and HMI_NODE relativity
====================================
Pages are full screen. Only one page is displayed at the same time.
Page change is triggered by ``HMI:Jump`` and ``HMI:Back``, or by changing ``/CURRENTPAGE_N``.
.. code-block:: text
HMI:Page:PageName[@RootPath]
HMI:Jump:PageName[@RelativePath]
HMI:Back
Absolute and relative pages
---------------------------
When ``[@RootPath]`` is given, page is relative.
When using ``HMI:Jump`` to reach a relative page, a compatible
``[@RelativePath]`` may be provided.
To be compatible, ``RootPath`` and ``RelativePath`` must both point to
HMI tree nodes of type ``HMI_NODE`` instanciated from same POU.
Every widget using a path descendant of ``RootPath`` in a relative
page is relative. Relative widgets get the ``RootPath`` section of
their path replaced by ``RelativePath``.
Relative page label::
HMI:Page:PageName
Absolute page label::
HMI:Page:PageName@RootPath
Example::
HMI:Page:PumpControl@/PUMP0
.. image:: svghmi_relative.svg
Jumps
-----
``HMI:Jump`` can have ``inactive``, ``active`` and ``disabled`` labeled children:
* ``inactive`` is shown when target page is not currently displayed
* ``active`` is shown when target page is currently displayed
* ``disabled`` is shown when relative page's RootPath is set to 0, disabling jump.
Relative page label::
HMI:Jump:PageName@RelativePath
Absolute page label::
HMI:Jump:PageName
Example::
HMI:Jump:PumpControl@/PUMP7
Back: Jump to previous page
----------------------------
``HMI:Back`` takes no parameter and goes back one step in page change history when clicked.
Special ``/CURRENT_PAGE_n`` variable
-----------------------------------
Each SVGHMI instance have its own ``/CURRENT_PAGE_n``, with ``n`` being the position of SVGHMI instance in Configuration Tree.
By reading ``/CURRENT_PAGE_n`` value, PLC knows last page being displayed in HMI. Variable is of type STRING, and formatted as follows::
PageName
..
TODO
Overlapping geometry
--------------------
If widget's bounding box is included in page bounding box, then widget is part of page.
..
TODO
Discarded element
-----------------
References frames
-----------------
References frames help to unclutter page and widgets.
..
TODO
Screensaver
-----------
..
TODO
Fading
------
..
TODO
Go full screen
--------------
..
TODO