=========
latex2dnd
=========

Generate an edX drag-and-drop problem, complete with draggable labels, problem image, and
solution image, from an input latex file.

Installation
============

    pip install -e git+https://github.com/mitocw/latex2dnd.git#egg=latex2dnd

Note that pdftoppm is needed.  With osX and macbrew:

    brew install netpbm poppler

A working latex installation is also required.

Usage
=====

Usage: latex2dnd [options] filename.tex

Options:

  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -v, --verbose         verbose messages
  -V, --very-verbose    very verbose messages
  -C, --can-reuse-labels
                        allow draggable labels to be reusable
  -s, --skip-latex-compilation
                        skip latex compilation
  -d OUTPUT_DIR, --output-directory=OUTPUT_DIR
                        Directory name for output PNG files
  -c CONFIG_FILE, --config-file=CONFIG_FILE
                        configuration file to load
  -r RESOLUTION, --resolution=RESOLUTION
                        Resolution of PNG files in DPI

Example
=======

Get quadratic.tex from the latex2dnd/testtex directory, and run this:

  latex2dnd quadratic.tex -r 220 -v

this will generate 220dpi images, with the files:

    quadratic_dnd.xml -- edX drag-and-drop question XML
    ./quadratic_dnd.png -- dnd problem image
    ./quadratic_dnd_sol.png -- dnd problem solution image
    9 dnd draggable image labels:
        ./quadratic_dnd_label1.png -- label '1'
        ./quadratic_dnd_label2.png -- label '2'
        ./quadratic_dnd_label3.png -- label '3'
        ./quadratic_dnd_label4.png -- label '4'
        ./quadratic_dnd_label5.png -- label '5'
        ./quadratic_dnd_label6.png -- label '6'
        ./quadratic_dnd_label7.png -- label '7'
        ./quadratic_dnd_label8.png -- label '8'
        ./quadratic_dnd_label9.png -- label '9'

Insert this into your course with (if you're using https://github.com/mitocw/latex2edx):

    \begin{edXproblem}{Latex to drag and drop test}{}
    
    \edXinclude{quadratic_dnd.xml}
    
    \end{edXproblem}    

and copy the png files to /static/images/quadratic/

LaTeX Macros
============

latex2dnd works by introducing three important new macros:

1. \DDlabel{label_name}{label_contents}  
    -- label_name = alphanumeric name (no spaces) for the draggable label
    -- label_contents = latex string for contents of label (math ok, e.g. $\sqrt{a+b}$)

2. \DDBox{box_name}{width}{height}{label_name}
    -- box_name = alphanumeric name (no spaces) for the target box
    -- width, height = size of target box
    -- label_name = name of label which gives correct label to go in this box (the answer)

3. \writeDDlabels[height]
    -- height = optional argument which specifies the height of the labels (widths are automatic)

Here is an example, giving the LaTeX code for a drag-and-drop question asking for the
quadratic equation roots formula to be filled in:

    \documentclass{article}
    \input{latex2dnd}
    
    \begin{document}
    
    % define drag-drop labels
    \DDlabel{term1}{$-b$}
    \DDlabel{term1p}{$+b$}
    \DDlabel{term2}{$b^2$}
    \DDlabel{dubexp}{$b^{2^\alpha}$}
    \DDlabel{dubsub}{$b_{2_\alpha}$}
    \DDlabel{fac}{$-4ac$}
    \DDlabel{facp}{$+4ac$}
    \DDlabel{ta}{$+2a$}
    \DDlabel{tam}{$-2a$}
    
    % shorthand macro to make all boxes the same size (6 by 4)
    \newcommand\DDB[2]{\DDbox{#1}{6ex}{4ex}{#2}}
    
    % the formula with boxes
    $$\lambda = \frac{\DDB{1}{term1}\pm \sqrt{\DDB{2}{term2}\DDB{3}{fac}}}{\DDB{4}{ta}}$$
    
    % output labels, with fixed box heights
    \writeDDlabels[4.3ex]
    
    \end{document}

Note that more labels are defined than just the correct ones.  This is the XML generated from the above example:

    <span>
      <customresponse>
       <drag_and_drop_input img="/static/images/quadratic/quadratic_dnd.png" target_outline="false" one_per_target="true" no_labels="true" label_bg_color="rgb(222, 139, 238)">
          <draggable id="term1" icon="/static/images/quadratic/quadratic_dnd_label1.png"/>
          <draggable id="term1p" icon="/static/images/quadratic/quadratic_dnd_label2.png"/>
          <draggable id="term2" icon="/static/images/quadratic/quadratic_dnd_label3.png"/>
          <draggable id="dubexp" icon="/static/images/quadratic/quadratic_dnd_label4.png"/>
          <draggable id="dubsub" icon="/static/images/quadratic/quadratic_dnd_label5.png"/>
          <draggable id="fac" icon="/static/images/quadratic/quadratic_dnd_label6.png"/>
          <draggable id="facp" icon="/static/images/quadratic/quadratic_dnd_label7.png"/>
          <draggable id="ta" icon="/static/images/quadratic/quadratic_dnd_label8.png"/>
          <draggable id="tam" icon="/static/images/quadratic/quadratic_dnd_label9.png"/>
          <target id="1" x="70" y="19" w="123" h="74"/>
          <!-- answer=term1 -->
          <target id="2" x="283" y="19" w="123" h="74"/>
          <!-- answer=term2 -->
          <target id="3" x="427" y="19" w="122" h="74"/>
          <!-- answer=fac -->
          <target id="4" x="249" y="129" w="122" h="74"/>
          <!-- answer=ta -->
        </drag_and_drop_input>
        <answer>
    caset = [{'term1': '1'}, {'term2': '2'}, {'fac': '3'}, {'ta': '4'}]
    ca = [ {"draggables": ca.keys(),"targets": ca.values(),"rule":"exact"} for ca in caset ]
    if draganddrop.grade(submission[0], ca):
        correct = ["correct"]
    else:
        correct = ["incorrect"]
    </answer>
      </customresponse>
      <solution>
        <img src="/static/images/quadratic/quadratic_dnd_sol.png"/>
      </solution>
    </span>

Advanced usage
==============

Here are some additional useful macros:

\DDoptions{} -- extra configuration parameters, e.g. HIDE_FORMULA_INPUT, CAN_REUSE, and ALLOW_EMPTY

\DDformula{ pattern }{ samples }{ expected } -- use formula checking to test correctness of drag-and-drop response.  For example:

    \DDformula{ [1] * [2] * [3] / [4] }{ G,m_1,m_2,d@1,1,1,1:20,20,20,20\#40 }{G*m_1*m_2/d^2}{}

\DDtest{ correct | incorrect }{ answer_box_ids }{ draggable_ids } -- unit test to perform on DDformula expressions, e.g.

    \DDtest{correct}{1,2,3,4}{G,m2,m1,d2}
    \DDtest{incorrect}{1,2,3,4}{G,d2,m1,m2}

Notes
=====

latex2dnd uses the "-region" feature of imagemagick's convert command,
to white out solution boxes and generate the problem image.  Version
7.0.4 of imagemagick appears to have a bug in how it handles
"-region", causing the region specification to be ignored, and thus
producing blank problem images (everything whited out).  If you
encounter this problem, one workaround is to back out to version 6.9.1
of imagemagick.

History
=======

* v0.9.0: python package, with unit tests
*     .1: add -C (can_reuse) flag
*     .2: improved box alignment and pixel position computation
*     .3: center labels in boxes; custom code when can_reuse=true
*     .4: add formula grading and gravity.tex example
*     .5: add \DDoptions{HIDE_FORMULA_INPUT} handling to not display formula input
*     .6: add \DDoptins{CUSTOM_CFN=xxx} and --cfn=xxx command line for custom DND result check function
* v1.0.0: add unit tests for DDformula, which automatically verify expected response is checked properly
