Task list items (extension)
GFM enables the
tasklist extension, where an additional processing step is performed on list items.
A task list item is a list item where the first block in it is a paragraph which begins with a task list item marker and at least one whitespace character before any other content.
A task list item marker consists of an optional number of spaces, a left bracket (
[), either a whitespace character or the letter
x in either lowercase or uppercase, and then a right bracket (
When rendered, the task list item marker is replaced with a semantic checkbox element; in an HTML output, this would be an
<input type="checkbox"> element.
If the character between the brackets is a whitespace character, the checkbox is unchecked. Otherwise, the checkbox is checked.
This spec does not define how the checkbox elements are interacted with: in practice, implementors are free to render the checkboxes as disabled or inmutable elements, or they may dynamically handle dynamic interactions (i.e. checking, unchecking) in the final rendered document.
Task lists can be arbitrarily nested: