..
   Copyright (c) 2018-2025 William Emerison Six

   Permission is granted to copy, distribute and/or modify this document
   under the terms of the GNU Free Documentation License, Version 1.3
   or any later version published by the Free Software Foundation;
   with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.

   A copy of the license is available at
   https://www.gnu.org/licenses/fdl-1.3.html.

***************************
Rotate the Square - Demo 12
***************************

Objective
^^^^^^^^^
Rotate the square around its origin.


.. figure:: static/screenshots/demo12.png
    :class: no-scale
    :align: center
    :alt: Demo 12
    :figclass: align-center

    Demo 12

How to Execute
^^^^^^^^^^^^^^

Load src/modelviewprojection/demo12.py in Spyder and hit the play button.


Move the Paddles using the Keyboard
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

==============  ==============================================
Keyboard Input  Action
==============  ==============================================
*w*             Move Left Paddle Up
*s*             Move Left Paddle Down
*k*             Move Right Paddle Down
*i*             Move Right Paddle Up

*d*             Increase Left Paddle's Rotation
*a*             Decrease Left Paddle's Rotation
*l*             Increase Right Paddle's Rotation
*j*             Decrease Right Paddle's Rotation

*UP*            Move the camera up, moving the objects down
*DOWN*          Move the camera down, moving the objects up
*LEFT*          Move the camera left, moving the objects right
*RIGHT*         Move the camera right, moving the objects left

*q*             Rotate the square around its center
==============  ==============================================

Description
^^^^^^^^^^^

Cayley Graph
^^^^^^^^^^^^


.. figure:: static/demo11.png
    :class: no-scale
    :align: center
    :alt: Demo 12
    :figclass: align-center

    Demo 12


Code
^^^^


Make a variable to determine the angle that the square will be rotated.

.. literalinclude:: ../../src/modelviewprojection/demo12.py
   :language: python
   :start-after: doc-region-begin define square rotation
   :end-before: doc-region-end define square rotation
   :linenos:
   :lineno-match:
   :caption: src/modelviewprojection/demo12.py


When 'q' is pressed, increase the angle.

.. literalinclude:: ../../src/modelviewprojection/demo12.py
   :language: python
   :start-after: doc-region-begin define handle input
   :end-before: doc-region-end define handle input
   :linenos:
   :lineno-match:
   :caption: src/modelviewprojection/demo12.py


::

    ...


Event Loop
~~~~~~~~~~

In the previous chapter, this was the rendering code for
the square.

.. literalinclude:: ../../src/modelviewprojection/demo11.py
   :language: python
   :start-after: doc-region-begin draw square
   :end-before: doc-region-end draw square
   :linenos:
   :lineno-match:
   :caption: src/modelviewprojection/demo11.py



Since we just want to add one rotation at the end of the sequence
of transformations from paddle 1 space to square space, just add
a rotate call at the top.



.. literalinclude:: ../../src/modelviewprojection/demo12.py
   :language: python
   :start-after: doc-region-begin draw square
   :end-before: doc-region-end draw square
   :linenos:
   :lineno-match:
   :caption: src/modelviewprojection/demo12.py


The author is getting really tired of having to look at all the different
transformation functions repeatedly defined for each object being drawn.