Commit 71acbe37 authored by webchick's avatar webchick

Issue #2216549 by jhodgdon, steveoliver: Fill in @defgroup/topic docs for Render overview.

parent b20ae794
......@@ -585,12 +585,73 @@
* @defgroup theme_render Theme system and Render API
* @{
* Overview of the theme system and render API
* @todo write this
* Additional documentation paragraphs need to be written, and functions,
* classes, and interfaces need to be added to this topic.
* Overview of the Theme system and Render API.
* The main purpose of Drupal's Theme system is to give themes complete control
* over the appearance of the site, which includes the markup returned from HTTP
* requests and the CSS files used to style that markup. In order to ensure that
* a theme can completely customize the markup, module developers should avoid
* directly writing HTML markup for pages, blocks, and other user-visible output
* in their modules, and instead return structured "render arrays" (described
* below). Doing this also increases usability, by ensuring that the markup used
* for similar functionality on different areas of the site is the same, which
* gives users fewer user interface patterns to learn.
* The core structure of the Render API is the render array, which is a
* hierarchical associative array containing data to be rendered and properties
* describing how the data should be rendered. A render array that is returned
* by a function to specify markup to be sent to the web browser or other
* services will eventually be rendered by a call to drupal_render(), which will
* recurse through the render array hierarchy if appropriate, making calls into
* the theme system to do the actual rendering. If a function or method actually
* needs to return rendered output rather than a render array, the best practice
* would be to create a render array, render it by calling drupal_render(), and
* return that result, rather than writing the markup directly. See the
* documentation of drupal_render() for more details of the rendering process.
* Each level in the hierarchy of a render array (including the outermost array)
* has one or more array elements. Array elements whose names start with '#' are
* known as "properties", and the array elements with other names are "children"
* (constituting the next level of the hierarchy); the names of children are
* flexible, while property names are specific to the Render API and the
* particular type of data being rendered. A special case of render arrays is a
* form array, which specifies the form elements for an HTML form; see the
* @link form_api Form generation topic @endlink for more information on forms.
* Render arrays (at each level in the hierarchy) will usually have one of the
* following three properties defined:
* - #type: Specifies that the array contains data and options for a particular
* type of "render element" (examples: 'form', for an HTML form; 'textfield',
* 'submit', and other HTML form element types; 'table', for a table with
* rows, columns, and headers). Modules define render elements by implementing
* hook_element_info(), which specifies the properties that are used in render
* arrays to provide the data and options, and default values for these
* properties. Look through implementations of hook_element_info() to discover
* what render elements are available.
* - #theme: Specifies that the array contains data to be themed by a particular
* theme hook. Modules define theme hooks by implementing hook_theme(), which
* specifies the input "variables" used to provide data and options; if a
* hook_theme() implementation specifies variable 'foo', then in a render
* array, you would provide this data using property '#foo'. Modules
* implementing hook_theme() also need to provide a default implementation for
* each of their theme hooks, normally in a Twig file. For more information
* and to discover available theme hooks, see the documentation of
* hook_theme() and the
* @link themeable Default theme implementations topic. @endlink
* - #markup: Specifies that the array provides HTML markup directly. Unless the
* markup is very simple, such as an explanation in a paragraph tag, it is
* normally preferable to use #theme or #type instead, so that the theme can
* customize the markup.
* For further information on the Theme and Render APIs, see:
* -
* -
* -
* -
* -
* @todo Check these links. Some are for Drupal 7, and might need updates for
* Drupal 8.
* @}
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