CommonMark

Block Rendering

Block renderers are responsible for converting the parsed AST elements into their HTML representation.

All block renderers should implement BlockRendererInterface and its render() method:

render()

The HtmlRenderer will call this method whenever a supported block element is encountered in the AST being rendered.

If the method can only handle certain block types, be sure to verify that you’ve been passed the correct type.

Parameters

Return value

The method must return the final HTML representation of the block and any of its contents. This can be an HtmlElement object (preferred; castable to a string), a string of raw HTML, or null if it could not render (and perhaps another renderer should give it a try).

You are responsible for handling any escaping that may be necessary.

Designating Block Renderers

When registering your render, you must tell the Environment which block element class your renderer should handle. For example:

<?php

$environment = Environment::createCommonMarkEnvironment();

// First param - the block class type that should use our renderer
// Second param - instance of the block renderer
$environment->addBlockRenderer(League\CommonMark\Block\Element\FencedCode::class, new MyCustomCodeRenderer());

A single renderer could even be used for multiple block types:

<?php

$environment = Environment::createCommonMarkEnvironment();

$myRenderer = new MyCustomCodeRenderer();

$environment->addBlockRenderer(League\CommonMark\Block\Element\FencedCode::class, $myRenderer, 10);
$environment->addBlockRenderer(League\CommonMark\Block\Element\IndentedCode::class, $myRenderer, 20);

Multiple renderers can be added per element type - when this happens, we use the result from the highest-priority renderer that returns a non-null result.

Example

Here’s a custom renderer which renders thematic breaks as text (instead of <hr>):

<?php

class TextDividerRenderer implements BlockRendererInterface
{
    public function render(AbstractBlock $block, ElementRendererInterface $htmlRenderer, $inTightList = false)
    {
        return new HtmlElement('pre', ['class' => 'divider'], '==============================');
    }
}

$environment = Environment::createCommonMarkEnvironment();
$environment->addBlockRenderer('League\CommonMark\Block\Element\ThematicBreak', new TextDividerRenderer());

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