Hacking at 0300

Markdown Extra (including Parsedown Extra) allows for attributes to be applied to certain elements: headers, fenced code blocks, links, and images. I'd like to be able to apply them to any element. I'm going to use the syntax of Python Markdown attributes, but the attribute lists go before the elements. For block level elements, they go on their own line before the element.

My attribute lists start with {: (not just {) and end with }. Anything that would be legal in HTML (as is fine, since I didn't write my own parser. I just used DOMDocument. There are three special cases:

• .foo is changed to class="foo". Note that this is different from the Python code, which appends class names that start with .. Repeated attribute names in actual HTML are ignored, so to use two classes, use class="foo bar", not .foo .bar.
• #foo is changed to id="foo".
• Two letters alone are changed to lang=xx, since I use that attribute so much.

Continue reading ‘Extending Parsedown: attributes’ »

Continuing work on extending Parsedown.

See the actual code.

Adding block-level elements is not much different from adding inline elements. Kavanot.name originally used <footer> elements to indicate the source of a block quote:

<blockquote>
    Do or do not. There is no try.
  </blockquote>
  <footer>Yoda</footer>
</blockquote>

While marking blockquotes this way is now acceptable, for a long time it wasn't, and the recommended way was with <figure> and <figcaption>. KavanotParsedown uses the latter model:

<figure>
  <blockquote>
    Do or do not. There is no try.
  <figcaption>Yoda</figcaption>
<figure>

But I start with creating a <footer> and then modifying the DOM. So I want to have a block element that I will indicate with "--" at the start of the line.

function __construct(){
  $this->BlockTypes['-'][] = 'Source'; // only line needed to indicate a block level element
  // ... rest of the constructor
}

protected function blockSource($Line, $Block = null){
  if (preg_match('/^--[ ]*(.+)/', $Line['text'], $matches)) {
    return array(
      'element' => array(
        'name' => 'footer',
        'handler' => array(
          'function' => 'lineElements',
          'argument' => $matches[1],
          'destination' => 'elements'
        ),
        'attributes' => array('class' => 'source') // for styling, add a class automatically
      )
    );
  }
}

so

>Do or do not. There is no try.
--Yoda

becomes

<blockquote>
    Do or do not. There is no try.
  <footer class="source" >Yoda</footer>
</blockquote>

I realized that I might want to add an attribution to an image as well, without it being in a <blockquote>, as

<p>
  <img src=/blog/blogfiles/pdf/smiley.png alt="Smile!"/>
  <footer class="source" >Some file I found on the web</footer>
</p>

But as it stands,

[Smile!](/blog/blogfiles/pdf/smiley.png)
--Some file I found on the web

doesn't work; the <p> ends before the <footer> starts:

<p>
  <img src=/blog/blogfiles/pdf/smiley.png alt="Smile!"/>
</p>
<footer class="source" >Some file I found on the web</footer>

so we need to check that the previous block wasn't a paragraph. If it was, then parse this line and add it to the paragraph as an internal element:

protected function blockSource($Line, $Block = null){
  if (preg_match('/^--[ ]*(.+)/', $Line['text'], $matches)) {
    if ($Block && $Block['type'] === 'Paragraph'){
      $Block['element']['handler']['argument'] .= "\n".$this->element($this->blockSource($Line)['element']);
      return $Block;
    }
    return array(
      'element' => array(
        'name' => 'footer',
        'handler' => array(
          'function' => 'lineElements',
          'argument' => $matches[1],
          'destination' => 'elements'
        ),
        'attributes' => array('class' => 'source') // for styling, add a class automatically
      )
    );
  }
}

and now it works, except that the footer is a child of the <p> instead of the <blockquote>. We'll have to fix that.

Extending Parsedown involves adding elements to the $InlineTypes and $BlockTypes arrays, then adding methods to handle them.

See the actual code.

Italics

I use <i> a lot, to indicate transliterated words. So I use could use "/" to indicate that:
/Shabbat/ is a Hebrew word becomes <i>Shabbat</i> is a Hebrew word. To do that:
do

class myParsedown extends Parsedown{
  function __construct(){
    $this->InlineTypes['/'] []= 'Italic';
    // after adding all the new inline types, create the list of characters
    $this->inlineMarkerList = implode ('', array_keys($this->InlineTypes));
    // allow the character to be escaped by '\'
    $this->specialCharacters []= '/';
  }

  protected function inlineItalic($excerpt){
    if (preg_match('#^/(.+?)/#', $excerpt['text'], $matches)) {
      return array(
        'extent' => strlen($matches[0]), 
        'element' => array(
          'name' => 'i',
          'handler' => array(
            'function' => 'lineElements',
            'argument' => $matches[1],
            'destination' => 'elements'
          )
        )
      );
    }
}

Now, my transliterated words are almost always Hebrew, so I can automatically add the lang=he attribute:

  protected function inlineItalic($excerpt){
    if (preg_match('#^/(.+?)/#', $excerpt['text'], $matches)) {
      return array(
        'extent' => strlen($matches[0]), 
        'element' => array(
          'name' => 'i',
          'handler' => array(
            'function' => 'lineElements',
            'argument' => $matches[1],
            'destination' => 'elements'
          ),
          'attributes' => array('lang' => 'he') // Add attributes
        )
      );
    }
}

and now /Shabbat/ is a Hebrew word becomes <i lang=he>Shabbat</i> is a Hebrew word.

Cite

I also use the <cite>. I'm running out of single characters to indicate elements, so I'm going to redefine "-". I don't need two different markers for <em>.

  function __construct(){
    $this->InlineTypes['_'] = ['Cite']; // redefinition; I am replacing the old array (which was ['Emphasis'])
    // ... rest of the constructor as above
  }

  protected function inlineCite($excerpt){
    if (preg_match('#^_(.+?)_#', $excerpt['text'], $matches)) {
      return array(
        'extent' => strlen($matches[0]), 
        'element' => array(
          'name' => 'cite',
          'handler' => array(
            'function' => 'lineElements',
            'argument' => $matches[1],
            'destination' => 'elements'
          )
        )
      );
    }

And now _A Tale of Two Cities_ becomes <cite>A Tale of Two Cities</cite>

Working with Parsedown, I want to string manipulation but only in certain parts. For instance, on text not in HTML tags or not in quotes. The right way to do that is with a real parser. The easy way is by removing the unwanted strings, replacing them with a marker that won't come up in normal text, doing the manipulation, then replacing the markers (it is the replacement step that requires "a marker that won't come up in normal text"; you don't want to replace text that was present in the original).

I would use a marker that can't be typed but still is legal HTML; turns out that U+FFFC (OBJECT REPLACEMENT CHARACTER, ) is perfect for that. So I made a pair of functions, `StringReplace\remove` and `StringReplace\restore` to make that easy.

StringReplace\remove ($re, $target)

Any string that matches the regular expression $re in $target is replaced by a numbered marker, "{number}". The new string is returned. So for instance,

$rawtext = StringReplace\remove ('#</?[^>]*>#', $html);

will remove tags.

StringReplace\restore ($target)

Returns a string with the markers replaced by their original versions.

The code

namespace StringReplace;

define ('OBJECT_REPLACEMENT_CHARACTER', '');
define ('RE_REPLACEMENT', '/'.OBJECT_REPLACEMENT_CHARACTER.'(\d+)'.OBJECT_REPLACEMENT_CHARACTER.'/');

$strings = array();

$remover = function ($matches){
  global $strings;
  $strings []= $matches[0];
  return OBJECT_REPLACEMENT_CHARACTER.count($strings).OBJECT_REPLACEMENT_CHARACTER;
};

$replacer = function ($matches){
  global $strings;
  return $strings[$matches[1]-1];
};

function remove ($re, $target){
  global $remover;
  return preg_replace_callback ($re, $remover, $target);
}

function restore ($target){
  global $replacer;
  return preg_replace_callback (RE_REPLACEMENT, $replacer, $target);
}

I've been spending all my intellectual free time on working on my Kavanot site, so I haven't been doing any independent programming. But that site uses raw HTML, which is a pain to type. So I decided to start using Markdown to make writing easier. After a little trial and error, I decided to use Parsedown with Parsedown Extra.

See the code.

Continue reading ‘Extending Parsedown’ »