============
VTK Backplot
============

The VTK Backplot is a very fast plot renderer and is the recommended one to use.

This example is using the :doc:`../tutorials/vcp_template` to create a blank
screen.

.. image:: images/backplot-01.png
   :align: center

Add a `Frame` and select frameShape `Box` then drag another `Frame` inside the
first one and select frameShape `Box` and drag a `VTKBackPlot` into the first
frame and save your work.

.. image:: images/backplot-02.png
   :align: center

Drag a couple of `Push Buttons` into the second frame. Right click inside the
first frame and select `Lay Out Vertically`.

.. image:: images/backplot-03.png
   :align: center

Double click on the first button and change the name to `P`, next change the
objectName to `plotP`. In the Signal/Slot Editor tab left click on the green
plus symbol to create a new Signal/Slot.

.. image:: images/backplot-04.png
   :align: center

Set the sender to `plotP`, set the Signal to `clicked()`, set the Receiver to
`vtkbackplot` and set the Slot to `setViewP()`. Now when we run the example
the first button will set the view to Isometric Projection.

.. image:: images/backplot-05.png
   :align: center

Controlling the display of the boundries and axes information can be done in the
configuration ini file located in `username/linuxcnc/configs/configuration_name`.
Descriptions of the options for the ini file are in 
:doc:`../configuration/ini_options`.

Turning off everything except `machine boundry` in the ini file.

.. image:: images/backplot-06.png
   :align: center

And the result.

.. image:: images/backplot-07.png
   :align: center

In the same mannor as before we can drag more buttons into the frame and set the
views for `X, Y, Z and Path`.

.. image:: images/backplot-08.png
   :align: center

Touch screens only have the left mouse button and the default action for the
left mouse button is to roll the disply. In order to pan the display we need to
add a button for Pan/Roll. Make sure to check off `checkable` so the function
will work.

The big difference with this buttons signal is it must be `clicked(bool)` for
the `enable_panning` slot to show up.

To change the text of the button to reflect the current status we need to do a
bit of python. Open the 
`username/configuration_name/configuration_name/mainwindow.py` file. Add the
`connect` line to tie the clicked action to the function. Then add the
`toggleRollPan` function.

::

  class MyMainWindow(VCPMainWindow):
	  """Main window class for the VCP."""
	  def __init__(self, *args, **kwargs):
		  super(MyMainWindow, self).__init__(*args, **kwargs)

		  self.plotRPBtn.clicked.connect(self.toggleRollPan)

	  def toggleRollPan(self):
		  if self.plotRPBtn.isChecked():
			  self.plotRPBtn.setText('Pan')
		  else:
			  self.plotRPBtn.setText('Roll')

Add a new signal with the sender plotRPBtn, signal clicked(bool), receiver
vtkbqackplot, slot enable_panning(bool).

.. image:: images/backplot-09.png
   :align: center

When we run the example and click or press the `Roll` button it toggles to the
`Pan` function and using a touch screen you can now pan the backplot.

.. image:: images/backplot-10.png
   :align: center