views.api.php

<?php


/**
 * @file
 * Describe hooks provided by the Views module.
 */

/**
 * @mainpage Views 3 API Manual
 *
 * Much of this information is actually stored in the advanced help; please
 * check the API topic. This help will primarily be aimed at documenting
 * classes and function calls.
 *
 * Topics:
 * - @link views_lifetime The life of a view @endlink
 * - @link views_hooks Views hooks @endlink
 * - @link views_handlers About Views handlers @endlink
 * - @link views_plugins About Views plugins @endlink
 * - @link views_templates Views template files @endlink
 * - @link views_module_handlers Views module handlers @endlink
 */

/**
 * @defgroup views_lifetime The life of a view
 * @{
 * This page explains the basic cycle of a view and what processes happen.
 *
 * @todo .
 * @}
 */

/**
 * @defgroup views_handlers About Views handlers
 * @{
 * In Views, a handler is an object that is part of the view and is part of the
 * query building flow.
 *
 * Handlers are objects; much of the time, the base handlers will work, but
 * often you'll need to override the handler to achieve something meaningful.
 * One typical handler override will be views_handler_filter_operator_in which
 * allows you to have a filter select from a list of options; you'll need to
 * override this to provide your list.
 *
 * Handlers have two distinct code flows; the UI flow and the view building
 * flow.
 *
 * For the query flow:
 * - handler->construct()
 *   - Create the initial handler; at this time it is not yet attached to a
 *     view. It is here that you can set basic defaults if needed, but there
 *     will be no knowledge of the environment yet.
 * - handler->set_definition()
 *   - Set the data from hook_views_data() relevant to the handler.
 * - handler->init()
 *   - Attach the handler to a view, and usually provides the options from the
 *     display.
 * - handler->pre_query()
 *   - Run prior to the query() stage to do early processing.
 * - handler->query()
 *   - Do the bulk of the work this handler needs to do to add itself to the
 *     query.
 *
 * Fields, being the only handlers concerned with output, also have an extended
 * piece of the flow:
 *
 * - handler->pre_render(&$values)
 *   - Called prior to the actual rendering, this allows handlers to query for
 *     extra data; the entire resultset is available here, and this is where
 *     items that have "multiple values" per record can do their extra query for
 *     all of the records available. There are several examples of this at work
 *     in the code, see for example views_handler_field_user_roles.
 * - handler->render()
 *   - This does the actual work of rendering the field.
 *
 * Most handlers are just extensions of existing classes with a few tweaks that
 * are specific to the field in question. For example,
 * views_handler_filter_in_operator provides a simple mechanism to set a
 * multiple-value list for setting filter values. Below,
 * views_handler_filter_node_type overrides the list options, but inherits
 * everything else.
 *
 * @code
 * class views_handler_filter_node_type extends views_handler_filter_in_operator {
 *   function get_value_options() {
 *     if (!isset($this->value_options)) {
 *       $this->value_title = t('Node type');
 *       $types = node_get_types();
 *       foreach ($types as $type => $info) {
 *         $options[$type] = $info->name;
 *       }
 *       $this->value_options = $options;
 *     }
 *   }
 * }
 * @endcode
 *
 * Handlers are stored in their own files and loaded on demand. Like all other
 * module files, they must first be registered through the module's info file.
 * For example:
 *
 * @code
 * name = Example module
 * description = "Gives an example of a module."
 * core = 7.x
 * files[] = example.module
 * files[] = example.install
 *
 * ; Views handlers
 * files[] = includes/views/handlers/example_handler_argument_string.inc
 * @endcode
 *
 * The best place to learn more about handlers and how they work is to explore
 * @link views_handlers Views' handlers @endlink and use existing handlers as a
 * guide and a model. Understanding how views_handler and its child classes work
 * is handy but you can do a lot just following these models. You can also
 * explore the views module directory, particularly node.views.inc.
 *
 * Please note that while all handler names in views are prefixed with views_,
 * you should use your own module's name to prefix your handler names in order
 * to ensure namespace safety. Note that the basic pattern for handler naming
 * goes like this:
 *
 * [module]_handler_[type]_[tablename]_[fieldname].
 *
 * Sometimes table and fieldname are not appropriate, but something that
 * resembles what the table/field would be can be used.
 *
 * See also:
 * - @link views_field_handlers Views field handlers @endlink
 * - @link views_sort_handlers Views sort handlers @endlink
 * - @link views_filter_handlers Views filter handlers @endlink
 * - @link views_argument_handlers Views argument handlers @endlink
 * - @link views_relationship_handlers Views relationship handlers @endlink
 * - @link views_area_handlers Views area handlers @endlink
 * @}
 */

/**
 * @defgroup views_plugins About Views plugins
 *
 * In Views, a plugin is a bit like a handler, but plugins are not directly
 * responsible for building the query. Instead, they are objects that are used
 * to display the view or make other modifications.
 *
 * There are several types of plugins in Views:
 * - Display: Display plugins are responsible for controlling *where* a view
 *   lives; that is, how they are being exposed to other parts of Drupal. Page
 *   and block are the most common displays, as well as the ubiquitous 'master'
 *   (or 'default') display.
 * - Style: Style plugins control how a view is displayed. For the most part
 *   they are object wrappers around theme templates. Styles could for example
 *   be HTML lists or tables.
 * - Row style: Row styles handle each individual record from the main view
 *   table. The two included by default render the entire entity (nodes only),
 *   or selected fields.
 * - Argument default: Argument default plugins allow pluggable ways of
 *   providing default values for contextual filters (previously 'arguments').
 *   This is useful for blocks and other display types lacking a natural
 *   argument input. Examples are plugins to extract node and user IDs from the
 *   URL.
 * - Argument validator: Validator plugins can ensure arguments are valid, and
 *   even do transformations on the arguments. They can also provide replacement
 *   patterns for the view title. For example, the 'content' validator
 *   verifies verifies that the argument value corresponds to a node, loads
 *   that node and provides the node title as a replacement pattern.
 * - Access: Access plugins are responsible for controlling access to the view.
 *   Views includes plugins for checking user roles and individual permissions.
 * - Query: Query plugins generate and execute a query, so they can be seen as
 *   a data backend. The default implementation is using SQL. There are
 *   contributed modules reading data from other sources, see for example the
 *   Views XML Backend module.
 * - Cache: Cache plugins control the storage and loading of caches. Currently
 *   they can do both result and render caching, but maybe one day cache the
 *   generated query.
 * - Pager plugins: Pager plugins take care of everything regarding pagers.
 *   From getting and setting the total amount of items to render the pager and
 *   setting the global pager arrays.
 * - Exposed form plugins: Exposed form plugins are responsible for building,
 *   rendering and controlling exposed forms. They can expose new parts of the
 *   view to the user and more.
 * - Localization plugins: Localization plugins take care how the view options
 *   are translated. There are example implementations for t(), 'no
 *   translation' and i18n.
 * - Display extenders: Display extender plugins allow scaling of views options
 *   horizontally. This means that you can add options and do stuff on all
 *   views displays. One theoretical example is metatags for views.
 *
 * Plugins are registered by implementing hook_views_plugins() in your
 * modulename.views.inc file and returning an array of data.
 * For examples please look at views_views_plugins() in
 * views/includes/plugins.inc as it has examples for all of them.
 *
 * Similar to handlers, make sure that you add your plugin files to the
 * module.info file.
 *
 * The array defining plugins will look something like this:
 * @code
 * return array(
 *   'display' => array(
 *     // ... list of display plugins,
 *    ),
 *   'style' => array(
 *     // ... list of style plugins,
 *    ),
 *   'row' => array(
 *     // ... list of row style plugins,
 *    ),
 *   'argument default' => array(
 *     // ... list of argument default plugins,
 *    ),
 *   'argument validator' => array(
 *     // ... list of argument validator plugins,
 *    ),
 *    'access' => array(
 *     // ... list of access plugins,
 *    ),
 *    'query' => array(
 *      // ... list of query plugins,
 *     ),,
 *    'cache' => array(
 *      // ... list of cache plugins,
 *     ),,
 *    'pager' => array(
 *      // ... list of pager plugins,
 *     ),,
 *    'exposed_form' => array(
 *      // ... list of exposed_form plugins,
 *     ),,
 *    'localization' => array(
 *      // ... list of localization plugins,
 *     ),
 *    'display_extender' => array(
 *      // ... list of display extender plugins,
 *     ),
 * );
 * @endcode
 *
 * Each plugin will be registered with an identifier for the plugin, plus a
 * fairly lengthy list of items that can define how and where the plugin is
 * used. Here is an example of a row style plugin from Views core:
 * @code
 *     'node' => array(
 *       'title' => t('Node'),
 *       'help' => t('Display the node with standard node view.'),
 *       'handler' => 'views_plugin_row_node_view',
 *       // Not necessary for most modules.
 *       'path' => drupal_get_path('module', 'views') . '/modules/node',
 *       'theme' => 'views_view_row_node',
 *       // Only works with 'node' as base.
 *       'base' => array('node'),
 *       'uses options' => TRUE,
 *       'type' => 'normal',
 *     ),
 * @endcode
 *
 * Of particular interest is the *path* directive, which works a little
 * differently from handler registration; each plugin must define its own path,
 * rather than relying on a global info for the paths. For example:
 * @code
 *    'feed' => array(
 *      'title' => t('Feed'),
 *      'help' => t('Display the view as a feed, such as an RSS feed.'),
 *      'handler' => 'views_plugin_display_feed',
 *      'uses hook menu' => TRUE,
 *      'use ajax' => FALSE,
 *      'use pager' => FALSE,
 *      'accept attachments' => FALSE,
 *      'admin' => t('Feed'),
 *      'help topic' => 'display-feed',
 *     ),
 * @endcode
 *
 * Please be sure to prefix your plugin identifiers with your module name to
 * ensure namespace safety; after all, two different modules could try to
 * implement the 'grid2' plugin, and that would cause one plugin to completely
 * fail.
 *
 * @todo Finish this document.
 *
 * See also:
 * - @link views_display_plugins Views display plugins @endlink
 * - @link views_style_plugins Views style plugins @endlink
 * - @link views_row_plugins Views row plugins @endlink
 */

/**
 * @defgroup views_hooks Views hooks
 * @{
 * Hooks that can be implemented by other modules in order to implement the
 * Views API.
 */

/**
 * Describes data tables (or the equivalent) to Views.
 *
 * This hook should be placed in MODULENAME.views.inc and it will be auto
 * loaded. MODULENAME.views.inc must be in the directory specified by the 'path'
 * key returned by MODULENAME_views_api(), or the same directory as the .module
 * file, if 'path' is unspecified.
 *
 * @return array
 *   An associative array describing the data structure. Primary key is the
 *   name used internally by Views for the table(s) – usually the actual table
 *   name. The values for the key entries are described in detail below.
 */
function hook_views_data() {
    // This example describes how to write hook_views_data() for the following
    // table:
    //
    // CREATE TABLE example_table (
    //   nid INT(11) NOT NULL COMMENT 'Primary key; refers to {node}.nid.',
    //   plain_text_field VARCHAR(32) COMMENT 'Just a plain text field.',
    //   numeric_field INT(11) COMMENT 'Just a numeric field.',
    //   boolean_field INT(1) COMMENT 'Just an on/off field.',
    //   timestamp_field INT(8) COMMENT 'Just a timestamp field.',
    //   PRIMARY KEY(nid)
    // );
    // First, the entry $data['example_table']['table'] describes properties of
    // the actual table – not its content.
    // The 'group' index will be used as a prefix in the UI for any of this
    // table's fields, sort criteria, etc. so it's easy to tell where they came
    // from.
    $data['example_table']['table']['group'] = t('Example table');
    // Define this as a base table – a table that can be described in itself by
    // views (and not just being brought in as a relationship). In reality this
    // is not very useful for this table, as it isn't really a distinct object of
    // its own, but it makes a good example.
    $data['example_table']['table']['base'] = array(
        // This is the identifier field for the view.
'field' => 'nid',
        'title' => t('Example table'),
        'help' => t('Example table contains example content and can be related to nodes.'),
        'weight' => -10,
    );
    // This table references the {node} table. The declaration below creates an
    // 'implicit' relationship to the node table, so that when 'node' is the base
    // table, the fields are automatically available.
    $data['example_table']['table']['join'] = array(
        // Index this array by the table name to which this table refers.
'node' => array(
            // The primary key in the referenced table.
'left_field' => 'nid',
            // The foreign key in this table.
'field' => 'nid',
        ),
    );
    // Next, describe each of the individual fields in this table to Views. This
    // is done by describing $data['example_table']['FIELD_NAME']. This part of
    // the array may then have further entries:
    //   - title: The label for the table field, as presented in Views.
    //   - help: The description text for the table field.
    //   - relationship: A description of any relationship handler for the table
    //     field.
    //   - field: A description of any field handler for the table field.
    //   - sort: A description of any sort handler for the table field.
    //   - filter: A description of any filter handler for the table field.
    //   - argument: A description of any argument handler for the table field.
    //   - area: A description of any handler for adding content to header,
    //     footer or as no result behaviour.
    //
    // The handler descriptions are described with examples below.
    // Node ID table field.
    $data['example_table']['nid'] = array(
        'title' => t('Example content'),
        'help' => t('Some example content that references a node.'),
        // Define a relationship to the {node} table, so example_table views can
        // add a relationship to nodes. If you want to define a relationship the
        // other direction, use hook_views_data_alter(), or use the 'implicit' join
        // method described above.
'relationship' => array(
            // The name of the table to join with.
'base' => 'node',
            // The name of the field on the joined table.
'base field' => 'nid',
            // 'field' => 'nid' -- see hook_views_data_alter(); not needed here.
'handler' => 'views_handler_relationship',
            'label' => t('Default label for the relationship'),
            'title' => t('Title shown when adding the relationship'),
            'help' => t('More information on this relationship'),
        ),
    );
    // Example plain text field.
    $data['example_table']['plain_text_field'] = array(
        'title' => t('Plain text field'),
        'help' => t('Just a plain text field.'),
        'field' => array(
            'handler' => 'views_handler_field',
            // This is use by the table display plugin.
'click sortable' => TRUE,
        ),
        'sort' => array(
            'handler' => 'views_handler_sort',
        ),
        'filter' => array(
            'handler' => 'views_handler_filter_string',
        ),
        'argument' => array(
            'handler' => 'views_handler_argument_string',
        ),
    );
    // Example numeric text field.
    $data['example_table']['numeric_field'] = array(
        'title' => t('Numeric field'),
        'help' => t('Just a numeric field.'),
        'field' => array(
            'handler' => 'views_handler_field_numeric',
            'click sortable' => TRUE,
        ),
        'filter' => array(
            'handler' => 'views_handler_filter_numeric',
        ),
        'sort' => array(
            'handler' => 'views_handler_sort',
        ),
    );
    // Example boolean field.
    $data['example_table']['boolean_field'] = array(
        'title' => t('Boolean field'),
        'help' => t('Just an on/off field.'),
        'field' => array(
            'handler' => 'views_handler_field_boolean',
            'click sortable' => TRUE,
        ),
        'filter' => array(
            'handler' => 'views_handler_filter_boolean_operator',
            // Note that you can override the field-wide label.
'label' => t('Published'),
            // This setting is used by the boolean filter handler, as possible option.
'type' => 'yes-no',
            // Use boolean_field = 1 instead of boolean_field <> 0 in WHERE statement.
'use equal' => TRUE,
        ),
        'sort' => array(
            'handler' => 'views_handler_sort',
        ),
    );
    // Example timestamp field.
    $data['example_table']['timestamp_field'] = array(
        'title' => t('Timestamp field'),
        'help' => t('Just a timestamp field.'),
        'field' => array(
            'handler' => 'views_handler_field_date',
            'click sortable' => TRUE,
        ),
        'sort' => array(
            'handler' => 'views_handler_sort_date',
        ),
        'filter' => array(
            'handler' => 'views_handler_filter_date',
        ),
    );
    return $data;
}

/**
 * Alter table structure.
 *
 * You can add/edit/remove existing tables defined by hook_views_data().
 *
 * This hook should be placed in MODULENAME.views_default.inc and it will be
 * auto-loaded. MODULENAME.views_default.inc must be in the directory specified
 * by the 'path' key returned by MODULENAME_views_api(), or the same directory
 * as the .module file, if 'path' is unspecified.
 *
 * After adding this hook to an existing module, you will need to clear the
 * Drupal menu cache and the Views cache to have your default views be
 * recognized.
 *
 * @param array $data
 *   An array of all Views data, passed by reference. See hook_views_data() for
 *   structure.
 *
 * @see hook_views_data()
 */
function hook_views_data_alter(&$data) {
    // This example alters the title of the node:nid field in the Views UI.
    $data['node']['nid']['title'] = t('Node-Nid');
    // This example adds an example field to the users table.
    $data['users']['example_field'] = array(
        'title' => t('Example field'),
        'help' => t('Some example content that references a user'),
        'field' => array(
            'handler' => 'modulename_handler_field_example_field',
        ),
    );
    // This example changes the handler of the node title field.
    // In this handler you could do stuff, like preview of the node when clicking
    // the node title.
    $data['node']['title']['field']['handler'] = 'modulename_handler_field_node_title';
    // This example adds a relationship to table {foo}, so that 'foo' views can
    // add this table using a relationship. Because we don't want to write over
    // the primary key field definition for the {foo}.fid field, we use a
    // placeholder field name as the key.
    $data['foo']['sample_name'] = array(
        'title' => t('Example relationship'),
        'help' => t('Example help'),
        'relationship' => array(
            // Table we're joining to.
'base' => 'example_table',
            // Field on the joined table.
'base field' => 'eid',
            // Real field name on the 'foo' table.
'field' => 'fid',
            'handler' => 'views_handler_relationship',
            'label' => t('Default label for relationship'),
            'title' => t('Title seen when adding relationship'),
            'help' => t('More information about relationship.'),
        ),
    );
    // Note that the $data array is not returned – it is modified by reference.
}

/**
 * Override the default data for a Field API field.
 *
 * Field module's Implements hook_views_data() invokes this for each
 * field in the module that defines the field type (as declared in the field
 * array). It is not invoked in other modules.
 *
 * If no hook implementation exists, hook_views_data() falls back to
 * field_views_field_default_views_data().
 *
 * @param array $field
 *   A field definition array, as returned by field_info_fields().
 *
 * @return array
 *   An array of views data, in the same format as the return value of
 *   hook_views_data().
 *
 * @see field_views_data()
 * @see hook_field_views_data_alter()
 * @see hook_field_views_data_views_data_alter()
 */
function hook_field_views_data($field) {
    return array();
}

/**
 * Alter the views data for a single Field API field.
 *
 * This is called even if there is no hook_field_views_data() implementation for
 * the field, and therefore may be used to alter the default data that
 * field_views_field_default_views_data() supplies for the field.
 *
 * @param array $result
 *   An array of views table data provided for a single field. This has the same
 *   format as the return value of hook_views_data().
 * @param array $field
 *   A field definition array, as returned by field_info_fields().
 * @param string $module
 *   The module that defines the field type.
 *
 * @see field_views_data()
 * @see hook_field_views_data()
 * @see hook_field_views_data_views_data_alter()
 */
function hook_field_views_data_alter(&$result, $field, $module) {
}

/**
 * Alter the views data on a per field basis.
 *
 * Field module's Implements hook_views_data_alter() invokes this for
 * each field in the module that defines the field type (as declared in the
 * field array). It is not invoked in other modules.
 *
 * Unlike hook_field_views_data_alter(), this operates on the whole of the views
 * data. This allows a field module to add data that concerns its fields to
 * other tables, which would not yet be defined at the point when
 * hook_field_views_data() and hook_field_views_data_alter() are invoked. For
 * example, entityreference adds reverse relationships on the tables for the
 * entities which are referenced by entityreference fields.
 *
 * (Note: this is weirdly named so as not to conflict with
 * hook_field_views_data_alter().)
 *
 * @see hook_field_views_data()
 * @see hook_field_views_data_alter()
 * @see field_views_data_alter()
 */
function hook_field_views_data_views_data_alter(&$data, $field) {
    $field_name = $field['field_name'];
    $data_key = 'field_data_' . $field_name;
    // Views data for this field is in $data[$data_key].
}

/**
 * Describes plugins defined by the module.
 *
 * This hook should be placed in MODULENAME.views.inc and it will be
 * auto-loaded. MODULENAME.views.inc must be in the directory specified by the
 * 'path' key returned by MODULENAME_views_api(), or the same directory as the
 * .module file, if 'path' is unspecified. All plugin files need to be
 * referenced in MODULENAME.info with the files[] directive.
 *
 * @return array
 *   An array on the form $plugins['PLUGIN TYPE']['PLUGIN NAME']. The plugin
 *   must be one of row, display, display_extender, style, argument default,
 *   argument validator, access, query, cache, pager, exposed_form or
 *   localization. The plugin name should be prefixed with your module name.
 *   The value for each entry is an associative array that may contain the
 *   following entries:
 *   - Used by all plugin types:
 *     - title (required): The name of the plugin, as shown in Views. Wrap in
 *       t().
 *     - handler (required): The name of the file containing the class
 *       describing the handler, which must also be the name of the handler's
 *       class.
 *     - path: Path to the handler. Only required if the handler is not placed
 *       in the same folder as the .module file or in the subfolder 'views'.
 *     - parent: The name of the plugin this plugin extends. Since Drupal 7 this
 *       is no longer required, but may still be useful from a code readability
 *       perspective.
 *     - no ui: Set to TRUE to denote that the plugin doesn't appear to be
 *       selectable in the ui, though on the api side they still exists.
 *     - uses options: Set to TRUE to denote that the plugin has an additional
 *       options form.
 *     - help: A short help text, wrapped in t() used as description on the
 *       plugin settings form.
 *     - help topic: The name of an entry by advanced help for the plugin.
 *     - theme: The name of a theme suggestion to use for the display.
 *     - js: An array with paths to js files that should be included for the
 *       display. Note that the path should be relative Drupal root, not module
 *       root.
 *     - type: Each plugin can specify a type parameter to group certain
 *       plugins together. For example all row plugins related to feeds are
 *       grouped together, because a rss style plugin only accepts feed row
 *       plugins.
 *
 *   - Used by display plugins:
 *     - admin: The administrative name of the display, as displayed on the
 *       Views overview and also used as default name for new displays. Wrap in
 *       t().
 *     - no remove: Set to TRUE to make the display non-removable. (Basically
 *       only used for the master/default display.)
 *     - use ajax: Set to TRUE to allow AJAX loads in the display. If it's
 *       disabled there will be no ajax option in the ui.
 *     - use pager: Set to TRUE to allow paging in the display.
 *     - use more: Set to TRUE to allow the 'use more' setting in the display.
 *     - accept attachments: Set to TRUE to allow attachment displays to be
 *       attached to this display type.
 *     - contextual links locations: An array with places where contextual links
 *       should be added. Can for example be 'page' or 'block'. If you don't
 *       specify it there will be contextual links around the rendered view. If
 *       this is not set or regions have been specified, views will display an
 *       option to 'hide contextual links'. Use an empty array if you do not
 *       want this.
 *     - uses hook menu: Set to TRUE to have the display included by
 *       views_menu_alter(). views_menu_alter executes then execute_hook_menu
 *       on the display object.
 *     - uses hook block: Set to TRUE to have the display included by
 *       views_block_info().
 *     - theme: The name of a theme suggestion to use for the display.
 *     - js: An array with paths to js files that should be included for the
 *       display. Note that the path should be relative Drupal root, not module
 *       root.
 *
 *   - Used by style plugins:
 *     - uses row plugin: Set to TRUE to allow row plugins for this style.
 *     - uses row class: Set to TRUE to allow the CSS class settings for rows.
 *     - uses fields: Set to TRUE to have the style plugin accept field
 *       handlers.
 *     - uses grouping: Set to TRUE to allow the grouping settings for rows.
 *     - even empty: May have the value 'even empty' to tell Views that the
 *       style should be rendered even if there are no results.
 *
 *   - Used by row plugins:
 *     - uses fields: Set to TRUE to have the row plugin accept field handlers.
 */
function hook_views_plugins() {
    $plugins = array();
    $plugins['argument validator'] = array(
        'taxonomy_term' => array(
            'title' => t('Taxonomy term'),
            'handler' => 'views_plugin_argument_validate_taxonomy_term',
            // Declaring path explicitly not necessary for most modules.
'path' => drupal_get_path('module', 'views') . '/modules/taxonomy',
        ),
    );
    return array(
        // This just tells our themes are elsewhere.
'module' => 'views',
        'argument validator' => array(
            'taxonomy_term' => array(
                'title' => t('Taxonomy term'),
                'handler' => 'views_plugin_argument_validate_taxonomy_term',
                // Declaring path explicitly not necessary for most modules.
'path' => drupal_get_path('module', 'views') . '/modules/taxonomy',
            ),
        ),
        'argument default' => array(
            'taxonomy_tid' => array(
                'title' => t('Taxonomy term ID from URL'),
                'handler' => 'views_plugin_argument_default_taxonomy_tid',
                'path' => drupal_get_path('module', 'views') . '/modules/taxonomy',
                'parent' => 'fixed',
            ),
        ),
    );
}

/**
 * Alter existing plugins data, defined by modules.
 *
 * @see hook_views_plugins()
 */
function hook_views_plugins_alter(&$plugins) {
    // Add apachesolr to the base of the node row plugin.
    $plugins['row']['node']['base'][] = 'apachesolr';
}

/**
 * Alter existing plugin option definitions.
 *
 * This can be used to edit default or add new option definitions to existing
 * plugins. The reason for doing this is that only overriding the relevent form
 * with hook_form_alter() is insufficent because submitted form values will be
 * ignored if they haven't been declared as an available option.
 *
 * An alternative approach you could also take is to extend each plugin
 * individually. However if your goal is to override many, or even all plugins,
 * this results in a lot of additional code and files. This makes it a lot more
 * troublesome to maintain the codebase, as well as interoperability with other
 * modules.
 *
 * @param array $options
 *   The option definitions to be altered.
 * @param $plugin
 *   A views object of the plugin where the default options are defined.
 *
 * @see views_object::option_definition()
 * @see hook_views_handler_option_definition_alter()
 * @see hook_form_alter()
 */
function hook_views_plugin_option_definition_alter(&$options, $plugin) {
    // Add a new option definition.
    $options['option_name'] = array(
        'default' => '',
    );
}

/**
 * Alter existing handler option definitions.
 *
 * This can be used to edit default or add new option definitions to existing
 * handlers. The reason for doing this is that only overriding the relevent form
 * with hook_form_alter() is insufficent because submitted form values will be
 * ignored if they haven't been declared as an available option.
 *
 * An alternative approach you could also take is to extend each handler
 * individually. However if your goal is to override many, or even all handlers,
 * this results in a lot of additional code and files. This makes it a lot more
 * troublesome to maintain the codebase, as well as interoperability with other
 * modules.
 *
 * @param array $options
 *   The option definitions to be altered.
 * @param $handler
 *   A views object of the handler where the default options are defined.
 *
 * @see views_handler::option_definition()
 * @see hook_views_plugin_option_definition_alter()
 * @see hook_form_alter()
 */
function hook_views_handler_option_definition_alter(&$options, $handler) {
    // Add a new option definition.
    $options['option_name'] = array(
        'default' => '',
    );
}

/**
 * Register View API information.
 *
 * This is required for your module to have its include files loaded; for
 * example, when implementing hook_views_default_views().
 *
 * @return array
 *   An array with the following possible keys:
 *   - api: (required) The version of the Views API the module implements.
 *   - path: (optional) If includes are stored somewhere other than within the
 *     root module directory, specify its path here.
 *   - template path: (optional) A path where the module has stored its views
 *     template files. When you have specified this key views automatically
 *     uses the template files for the views. You can use the same naming
 *     conventions like for normal views template files.
 */
function hook_views_api() {
    return array(
        'api' => 3,
        'path' => drupal_get_path('module', 'example') . '/includes/views',
        'template path' => drupal_get_path('module', 'example') . '/themes',
    );
}

/**
 * Allows modules to provide their own views.
 *
 * These can either be used as-is or as a "starter" for users to build from.
 *
 * This hook should be placed in MODULENAME.views_default.inc and it will be
 * auto-loaded. MODULENAME.views_default.inc must be in the directory specified
 * by the 'path' key returned by MODULENAME_views_api(), or the same directory
 * as the .module file, if 'path' is unspecified.
 *
 * The $view->disabled boolean flag indicates whether the View should be
 * enabled (FALSE) or disabled (TRUE) by default.
 *
 * @return array
 *   An associative array containing the structures of views, as generated from
 *   the Export tab, keyed by the view name. A best practice is to go through
 *   and add t() to all title and label strings, with the exception of menu
 *   strings.
 */
function hook_views_default_views() {
    // Begin copy and paste of output from the Export tab of a view.
    $view = new view();
    $view->name = 'frontpage';
    $view->description = 'Emulates the default Drupal front page; you may set the default home page path to this view to make it your front page.';
    $view->tag = 'default';
    $view->base_table = 'node';
    $view->human_name = 'Front page';
    $view->core = 0;
    $view->api_version = '3.0';
    $view->disabled = FALSE;
    
    /* Edit this to true to make a default view disabled initially */
    
    /* Display: Master */
    $handler = $view->new_display('default', 'Master', 'default');
    $handler->display->display_options['access']['type'] = 'none';
    $handler->display->display_options['cache']['type'] = 'none';
    $handler->display->display_options['query']['type'] = 'views_query';
    $handler->display->display_options['query']['options']['query_comment'] = FALSE;
    $handler->display->display_options['exposed_form']['type'] = 'basic';
    $handler->display->display_options['pager']['type'] = 'full';
    $handler->display->display_options['style_plugin'] = 'default';
    $handler->display->display_options['row_plugin'] = 'node';
    
    /* Sort criterion: Content: Sticky */
    $handler->display->display_options['sorts']['sticky']['id'] = 'sticky';
    $handler->display->display_options['sorts']['sticky']['table'] = 'node';
    $handler->display->display_options['sorts']['sticky']['field'] = 'sticky';
    $handler->display->display_options['sorts']['sticky']['order'] = 'DESC';
    
    /* Sort criterion: Content: Post date */
    $handler->display->display_options['sorts']['created']['id'] = 'created';
    $handler->display->display_options['sorts']['created']['table'] = 'node';
    $handler->display->display_options['sorts']['created']['field'] = 'created';
    $handler->display->display_options['sorts']['created']['order'] = 'DESC';
    
    /* Filter criterion: Content: Promoted to front page */
    $handler->display->display_options['filters']['promote']['id'] = 'promote';
    $handler->display->display_options['filters']['promote']['table'] = 'node';
    $handler->display->display_options['filters']['promote']['field'] = 'promote';
    $handler->display->display_options['filters']['promote']['value'] = '1';
    $handler->display->display_options['filters']['promote']['group'] = 0;
    $handler->display->display_options['filters']['promote']['expose']['operator'] = FALSE;
    
    /* Filter criterion: Content: Published */
    $handler->display->display_options['filters']['status']['id'] = 'status';
    $handler->display->display_options['filters']['status']['table'] = 'node';
    $handler->display->display_options['filters']['status']['field'] = 'status';
    $handler->display->display_options['filters']['status']['value'] = '1';
    $handler->display->display_options['filters']['status']['group'] = 0;
    $handler->display->display_options['filters']['status']['expose']['operator'] = FALSE;
    
    /* Display: Page */
    $handler = $view->new_display('page', 'Page', 'page');
    $handler->display->display_options['path'] = 'frontpage';
    
    /* Display: Feed */
    $handler = $view->new_display('feed', 'Feed', 'feed');
    $handler->display->display_options['defaults']['title'] = FALSE;
    $handler->display->display_options['title'] = 'Front page feed';
    $handler->display->display_options['pager']['type'] = 'some';
    $handler->display->display_options['style_plugin'] = 'rss';
    $handler->display->display_options['row_plugin'] = 'node_rss';
    $handler->display->display_options['path'] = 'rss.xml';
    $handler->display->display_options['displays'] = array(
        'default' => 'default',
        'page' => 'page',
    );
    $handler->display->display_options['sitename_title'] = '1';
    // (Export ends here.)
    // Add view to list of views to provide.
    $views[$view->name] = $view;
    // Repeat all of the above for each view the module should provide. At the
    // end, return array of default views.
    return $views;
}

/**
 * Alter default views defined by other modules.
 *
 * This hook is called right before all default views are cached to the
 * database. It takes a keyed array of views by reference.
 *
 * Example usage to add a field to a view:
 * @code
 *   $handler =& $view->display['DISPLAY_ID']->handler;
 *   // Add the user name field to the view.
 *   $handler->display->display_options['fields']['name']['id'] = 'name';
 *   $handler->display->display_options['fields']['name']['table'] = 'users';
 *   $handler->display->display_options['fields']['name']['field'] = 'name';
 *   $handler->display->display_options['fields']['name']['label'] = 'Author';
 *   $handler->display->display_options['fields']['name']['link_to_user'] = 1;
 * @endcode
 */
function hook_views_default_views_alter(&$views) {
    if (isset($views['taxonomy_term'])) {
        $views['taxonomy_term']->display['default']->display_options['title'] = 'Categories';
    }
}

/**
 * Performs replacements in the query before being performed.
 *
 * @param object $view
 *   The View being executed.
 *
 * @return array
 *   An array with keys being the strings to replace, and the values the strings
 *   to replace them with. The strings to replace are often surrounded with
 *   '***', as illustrated in the example implementation.
 */
function hook_views_query_substitutions($view) {
    // Example from views_views_query_substitutions().
    global $language_content;
    return array(
        '***CURRENT_VERSION***' => VERSION,
        '***CURRENT_TIME***' => REQUEST_TIME,
        '***CURRENT_LANGUAGE***' => $language_content->language,
        '***DEFAULT_LANGUAGE***' => language_default('language'),
    );
}

/**
 * This hook is called to get a list of placeholders and their substitutions.
 *
 * Used when preprocessing a View with form elements.
 *
 * @return array
 *   An array with keys being the strings to replace, and the values the strings
 *   to replace them with.
 */
function hook_views_form_substitutions() {
    return array(
        '<!--views-form-example-substitutions-->' => 'Example Substitution',
    );
}

/**
 * Allows altering a view at the very beginning of processing a preview.
 *
 * Occurs before anything is done.
 *
 * This hook is only triggered when the one of the following are invoked:
 * - $view->execute_display()
 * - $view->preview()
 *
 * As such code placed in this hook will not fire during:
 * - $view->build()
 * - $view->execute()
 * - $view->render()
 *
 * Likely, hook_views_pre_build() or hook_views_pre_execute() are much better
 * choices for most use cases since they are always invoked, not just when
 * previewing a display.
 *
 * Adding output to the view can be accomplished by placing text on
 * $view->attachment_before and $view->attachment_after.
 *
 * @param object $view
 *   The view object about to be processed.
 * @param string $display_id
 *   The machine name of the active display.
 * @param array $args
 *   An array of arguments passed into the view.
 */
function hook_views_pre_view(&$view, &$display_id, &$args) {
    // Change the display if the acting user has 'administer site configuration'
    // permission, to display something radically different.
    // (Note that this is not necessarily the best way to solve that task. Feel
    // free to contribute another example!)
    if ($view->name == 'my_special_view' && user_access('administer site configuration') && $display_id == 'public_display') {
        $view->set_display('private_display');
    }
}

/**
 * Called after the display's pre_execute phase but before the build process.
 *
 * Adding output to the view can be accomplished by placing text on
 * $view->attachment_before and $view->attachment_after.
 *
 * @param object $view
 *   The view object about to be processed.
 */
function hook_views_pre_build(&$view) {
    // Because of some inexplicable business logic, we should remove all
    // attachments from all views on Mondays.
    // (This alter could be done later in the execution process as well.)
    if (date('D') == 'Mon') {
        unset($view->attachment_before);
        unset($view->attachment_after);
    }
}

/**
 * This hook is called right after the build process.
 *
 * The query is now fully built, but it has not yet been run through
 * db_rewrite_sql.
 *
 * Adding output to the view can be accomplished by placing text on
 * $view->attachment_before and $view->attachment_after.
 *
 * @param object $view
 *   The view object about to be processed.
 */
function hook_views_post_build(&$view) {
    // If the exposed field 'type' is set, hide the column containing the content
    // type. (Note that this is a solution for a particular view, and makes
    // assumptions about both exposed filter settings and the fields in the view.
    // Also note that this alter could be done at any point before the view being
    // rendered.)
    if ($view->name == 'my_view' && isset($view->exposed_raw_input['type']) && $view->exposed_raw_input['type'] != 'All') {
        // 'Type' should be interpreted as content type.
        if (isset($view->field['type'])) {
            $view->field['type']->options['exclude'] = TRUE;
        }
    }
}

/**
 * This hook is called right before the execute process.
 *
 * The query is now fully built, but it has not yet been run through
 * db_rewrite_sql.
 *
 * Adding output to the view can be accomplished by placing text on
 * $view->attachment_before and $view->attachment_after.
 *
 * @param object $view
 *   The view object about to be processed.
 */
function hook_views_pre_execute(&$view) {
    // Whenever a view queries more than two tables, show a message that notifies
    // view administrators that the query might be heavy.
    // (This action could be performed later in the execution process, but not
    // earlier.)
    if (count($view->query->tables) > 2 && user_access('administer views')) {
        drupal_set_message(t('The view %view may be heavy to execute.', array(
            '%view' => $view->name,
        )), 'warning');
    }
}

/**
 * This hook is called right after the execute process.
 *
 * The query has been executed, but the pre_render() phase has not yet happened
 * for handlers.
 *
 * Adding output to the view can be accomplished by placing text on
 * $view->attachment_before and $view->attachment_after. Altering the content
 * can be achieved by editing the items of $view->result.
 *
 * @param object $view
 *   The view object about to be processed.
 */
function hook_views_post_execute(&$view) {
    // If there are more than 100 results, show a message that encourages the user
    // to change the filter settings.
    // (This action could be performed later in the execution process, but not
    // earlier.)
    if ($view->total_rows > 100) {
        drupal_set_message(t('You have more than 100 hits. Use the filter settings to narrow down your list.'));
    }
}

/**
 * This hook is called right before the render process.
 *
 * The query has been executed, and the pre_render() phase has already happened
 * for handlers, so all data should be available.
 *
 * Adding output to the view can be accomplished by placing text on
 * $view->attachment_before and $view->attachment_after. Altering the content
 * can be achieved by editing the items of $view->result.
 *
 * This hook can be utilized by themes.
 *
 * @param object $view
 *   The view object about to be processed.
 */
function hook_views_pre_render(&$view) {
    // Scramble the order of the rows shown on this result page.
    // Note that this could be done earlier, but not later in the view execution
    // process.
    shuffle($view->result);
}

/**
 * Post process any rendered data.
 *
 * This can be valuable to be able to cache a view and still have some level of
 * dynamic output. In an ideal world, the actual output will include HTML
 * comment based tokens, and then the post process can replace those tokens.
 *
 * Example usage. If it is known that the view is a node view and that the
 * primary field will be a nid, you can do something like this:
 *
 * <!--post-FIELD-NID-->
 *
 * And then in the post render, create an array with the text that should
 * go there:
 *
 * strtr($output, array('<!--post-FIELD-1-->' => 'output for FIELD of nid 1');
 *
 * All of the cached result data will be available in $view->result, as well,
 * so all ids used in the query should be discoverable.
 *
 * This hook can be utilized by themes.
 *
 * @param object $view
 *   The view object about to be processed.
 * @param string $output
 *   A flat string with the rendered output of the view.
 * @param array $cache
 *   The cache settings.
 */
function hook_views_post_render(&$view, &$output, &$cache) {
    // When using full pager, disable any time-based caching if there are less
    // then 10 results.
    if ($view->query->pager instanceof views_plugin_pager_full && $cache->options['type'] == 'time' && count($view->result) < 10) {
        $cache['options']['results_lifespan'] = 0;
        $cache['options']['output_lifespan'] = 0;
    }
}

/**
 * Alter the query before executing the query.
 *
 * This hook should be placed in MODULENAME.views.inc and it will be
 * auto-loaded. MODULENAME.views.inc must be in the directory specified by the
 * 'path' key returned by MODULENAME_views_api(), or the same directory as the
 * .module file, if 'path' is unspecified.
 *
 * @param object $view
 *   The view object about to be processed.
 * @param object $query
 *   An object describing the query.
 *
 * @see hook_views_query_substitutions()
 */
function hook_views_query_alter(&$view, &$query) {
    // (Example assuming a view with an exposed filter on node title.)
    // If the input for the title filter is a positive integer, filter against
    // node ID instead of node title.
    if ($view->name == 'my_view' && is_numeric($view->exposed_raw_input['title']) && $view->exposed_raw_input['title'] > 0) {
        // Traverse through the 'where' part of the query.
        foreach ($query->where as &$condition_group) {
            foreach ($condition_group['conditions'] as &$condition) {
                // If this is the part of the query filtering on title, change the
                // condition to filter on node ID.
                if ($condition['field'] == 'node.title') {
                    $condition = array(
                        'field' => 'node.nid',
                        'value' => $view->exposed_raw_input['title'],
                        'operator' => '=',
                    );
                }
            }
            unset($condition);
        }
        unset($condition_group);
    }
}

/**
 * Alter the information box that (optionally) appears with a view preview.
 *
 * Includes query and performance statistics.
 *
 * This hook should be placed in MODULENAME.views.inc and it will be
 * auto-loaded. MODULENAME.views.inc must be in the directory specified by the
 * 'path' key returned by MODULENAME_views_api(), or the same directory as the
 * .module file, if 'path' is unspecified.
 *
 * Warning: $view is not a reference in PHP4 and cannot be modified here. But it
 * IS a reference in PHP5, and can be modified. Please be careful with it.
 *
 * @param array $rows
 *   An associative array with two keys:
 *   - query: An array of rows suitable for theme('table'), containing
 *     information about the query and the display title and path.
 *   - statistics: An array of rows suitable for theme('table'), containing
 *     performance statistics.
 * @param object $view
 *   The view object.
 *
 * @see theme_table()
 */
function hook_views_preview_info_alter(&$rows, $view) {
    // Adds information about the tables being queried by the view to the query
    // part of the info box.
    $rows['query'][] = array(
        t('<strong>Table queue</strong>'),
        count($view->query->table_queue) . ': (' . implode(', ', array_keys($view->query->table_queue)) . ')',
    );
}

/**
 * This hooks allows to alter the links at the top of the view edit form.
 *
 * Some modules might want to add links there.
 *
 * @param array $links
 *   An array of links which will be displayed at the top of the view edit form.
 *   Each entry should be on a form suitable for theme('link').
 * @param object $view
 *   The full view object which is currently edited.
 * @param string $display_id
 *   The current display id which is edited. For example that's 'default' or
 *   'page_1'.
 */
function hook_views_ui_display_top_links_alter(&$links, $view, $display_id) {
    // Put the export link first in the list.
    if (isset($links['export'])) {
        $links = array(
            'export' => $links['export'],
        ) + $links;
    }
}

/**
 * This hooks allows you to alter the ajax form definitions for the sub-forms
 * that handle the editing of the different pieces of a view, for example
 * adding or editing fields or filters.
 *
 * Other modules may want to change existing form callbacks or add their own
 * new forms.
 *
 * @param array $forms
 *   An array of forms where the keys are keys, that are passed in via the url
 *   and are used to identify the forms, and the values are arrays of
 *   information defining the form, including the form id and the arguments.
 *
 * @see views_ui_ajax_forms()
 */
function hook_views_ui_ajax_forms_alter(&$forms) {
    // Add a new custom form for categorizing fields, filters, etc. attached to
    // the view. You would then implement the form function
    // mymodule_views_categorize_fields_form($form, &$form_state) and $form_state
    // would contain $form_state['type'] and $form_state['id'].
    // The urls that would call this form would be (both nojs and ajax versions):
    // admin/structure/views/nojs/categorise-item/<view_name>/<display_name>/<type>/<id>
    // admin/structure/views/ajax/categorise-item/<view_name>/<display_name>/<type>/<id>.
    $forms['categorise-item'] = array(
        'form_id' => 'mymodule_views_categorize_fields_form',
        'args' => array(
            'type',
            'id',
        ),
    );
    // Modify the add-item form callback.
    // You would then implement the form function
    // mymodule_add_item_form_custom(), which would override the existing
    // views_ui_add_item_form().
    // Note that you would likely use hook_form_alter() in this case instead of
    // doing this, this is just an example.
    $forms['add-item']['form_id'] = 'mymodule_add_item_form_custom';
}

/**
 * Allows altering the commands which are used on a views AJAX request.
 *
 * @param array $commands
 *   An array of ajax commands.
 * @param object $view
 *   The view which is requested.
 */
function hook_views_ajax_data_alter(&$commands, $view) {
    // Replace Views' method for scrolling to the top of the element with your
    // custom scrolling method.
    foreach ($commands as &$command) {
        if ($command['command'] == 'viewsScrollTop') {
            $command['command'] .= 'myScrollTop';
        }
    }
    unset($command);
}

/**
 * Allow modules to respond to the Views cache being invalidated.
 *
 * This hook should fire whenever a view is enabled, disabled, created,
 * updated, or deleted.
 *
 * @param string $cid
 *   The cache identifier that is being cleared.
 *
 * @see views_invalidate_cache()
 */
function hook_views_invalidate_cache($cid) {
    cache_clear_all('views:*', 'cache_mymodule', TRUE);
}

/**
 * Allow modules to alter a view prior to being saved.
 */
function hook_views_view_presave($view) {
    // Do some adjustments to the view. Handle with care.
    if (mymodule_check_view($view)) {
        mymodule_do_some_voodoo($view);
    }
}

/**
 * Allow modules to respond to a view being saved.
 */
function hook_views_view_save($view) {
    // Make a watchdog entry.
    watchdog('views', 'The view @name was deleted by @user at @time', array(
        '@name' => $view->name,
        '@user' => $GLOBALS['user']->name,
        '@time' => format_date(time()),
    ));
}

/**
 * Allow modules to respond to a view being deleted or reverted.
 */
function hook_views_view_delete($view) {
    // Make a watchdog entry.
    watchdog('views', 'The view @name was deleted by @user at @time', array(
        '@name' => $view->name,
        '@user' => $GLOBALS['user']->name,
        '@time' => format_date(time()),
    ));
}

/**
 * @}
 */

/**
 * @defgroup views_module_handlers Views module handlers
 * @{
 * Handlers exposed by various modules to Views.
 * @}
 */