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Nov 14th, 2022
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Do to 
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* Brief introduction to beamer class, https://www.overleaf.com/learn/latex/Beamer
* More thorough treatments starts here, https://www.overleaf.com/learn/latex/Beamer_Presentations%3A_A_Tutorial_for_Beginners_(Part_1)%E2%80%94Getting_Started
* Beamer ``pause, overlay``, 
  
.. .. note:: 

..     I apologize for the missing images below. Please use https://www.overleaf.com/read/pnjfsjgwjnyv (under the beamer example folder) for the reference of images. 

Beamer Overlay
----------------

These notes are based on https://www.overleaf.com/learn/latex/Beamer_Presentations%3A_A_Tutorial_for_Beginners_(Part_4)%E2%80%94Getting_Started. 

Recall that the page unit in the Beamer class is a frame. 
Sometimes, we want to present information dynamically, meaning display part of the frame before displaying the whole frame. 
There are a few ways to do this with the Beamer class. 
They are often called ``overlay`` and Overleaf provides a good explanation. 
Below is the list of commands for overlay.

**Overlay**
  * ``\pause``
  * ``\item<n>``
  * ``\overlay``
  * ``\only``

.. note:: 

    When using this commands, the outcome file becomes big quickly. 
    When you want framewise outcomes, use the option ``handout`` instead of deleting or commenting out overlay commands. E.g., 

    ``\documentclass[handouts]{beamer}``

pause
~~~~~~~~~~~

The ``\pause`` commands simply pauses where it is placed and continues. The following code will produce the following outcomes

.. code-block:: latex
  :caption: Beamer pause example

  \begin{frame}{pause example}
  First slide 
  \pause
  Next slide
  \end{frame}

You may place ``\pause`` as many time as you like.

item<n->
~~~~~~~~~~~

Unlike the ``article`` or ``amsart`` classes, the ``itemize`` and ``enumerate`` commands in the ``beamer`` class have additional features for overlay. Here are some of the ways to use them.

.. code-block:: latex
  :caption: Beamer item<n-> example

  \begin{frame}{itemize example}
  \begin{itemize}
    \item<1> something      % shows this item only on slide 1
    \item<2> something      % shows this item only on slide 2
    \item<1-2> something    % shows this item only on slides 1,2
    \item<1-3> something    % shows this item only on slides 1,2,3
    \item<2-> something     % shows this item from on slide 2 to the last one.
    \item<1,3-> something   % shows this item only on slide 1 and slide 3 to the last one.
  \end{itemize}
  \end{frame}

overlay
~~~~~~~

The ``overlay`` command works the same as itemize. 
The only difference is that one does not need to use ``itemize`` or ``enuemrate`` but needs to include them in the parenthesis.

.. code-block:: latex
  :caption: Beamer overlay example

  \begin{frame}{itemize example}
  \overlay<1>{something}      % shows this item only on slide 1
  \overlay<2>{something}      % shows this item only on slide 2
  \overlay<1-2>{something}    % shows this item only on slides 1,2
  \overlay<1-3>{something}    % shows this item only on slides 1,2,3
  \overlay<2->{something}     % shows this item from on slide 2 to the last one.
  \overlay<1,3->{something}   % shows this item only on slide 1 and slide 3 to the last one.
  \end{frame}

.. note:: 

  One can use the same option for the block environments 

  .. code-block:: latex 
    :caption: Beamer overlay theorem example

    \begin{theorem}<1>
    My theorem
    \end{theorem}
  

only
~~~~

As the name says, ``\only<1>{something}`` displays the item on slide 1 only. 
Only works differently compared to the rest as it does not keep its place when not used. 
That is, the following code will create three slides where the position of each line is the same. 

.. code-block:: latex
  :caption: Beamer only example

  \begin{frame}{itemize example}
  \only<1>{something1} 
  \only<2>{something2} 
  \only<3>{something3} 
  \end{frame}

Options
~~~~~~~~

When using the overlay commands, sometimes it is hard to remember. 
Play with the following options to see which one works the best for your presentation. 

.. code-block:: latex

  \begin{frame}{itemize example}
  \setbeamercovered{invisible}    % default option
  \setbeamercovered{visible}      
  \setbeamercovered{transparent}  
  \end{frame}