The Block Hooks mechanism was previously extended to allow insertion of a block as a Navigation block's first or last child. This was implemented by storing the `ignoredHookedBlocks` array in the corresponding `wp_navigation` post's post meta (instead of a metadata attribute on the anchor block).
This changeset extends that mechanism to Template Part blocks, by storing said metadata in the corresponding `wp_template_part` post's post meta, thus allowing extenders to use Block Hooks to insert a block as a Template Part block's first or last child, respectively.
Props tomjcafferkey, bernhard-reiter.
Fixes#60854.
Built from https://develop.svn.wordpress.org/trunk@58614
git-svn-id: http://core.svn.wordpress.org/trunk@58047 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Replaces `trigger_error()` with `wp_trigger_error()`.
The usage of `wp_trigger_error()` avoids generating `E_USER` family errors unless `WP_DEBUG` is on. In doing so, users should not see these messages in normal production.
Notes:
* Removes `E_USER_NOTICE` when passed as an argumnent, as it's the default error level.
* An empty string is passed for the function name when its name is already in the error message or does not add value to the error message.
* Externally maintained libraries are not included.
Follow-up to [55204], [25956], [29630], [38883], [52062], [52049], [54272], [38883], [55245], [51599], [14452], [38883], [24976].
Props prasadkarmalkar, rajinsharwar, thelovekesh, hellofromTonya, swissspidy.
Fixes#59652.
Built from https://develop.svn.wordpress.org/trunk@58409
git-svn-id: http://core.svn.wordpress.org/trunk@57858 1a063a9b-81f0-0310-95a4-ce76da25c4cd
As of [57790], the Templates endpoint uses the `rest_pre_insert_*` filter to inject the `ignoredHookedBlocks` metadata attribute into anchor blocks, prior to persisting a template or template part to the database. The same principle was implemented for the Navigation endpoint (where additionally, first and last child blocks added at the top level are store in the `wp_navigation` post object's post meta). The required logic was added to the Navigation block's code, i.e. inside the Gutenberg code repository, and then synchronized to Core.
In order to harmonize the code between the two endpoints, this changeset introduces a new `update_ignored_hooked_blocks_postmeta` function, which is based on the Navigation block's `block_core_navigation_update_ignore_hooked_blocks_meta`, alongside a few helper functions, and hooks it to the `rest_pre_insert_wp_navigation` filter hook. (The Navigation block has been prepared in [58275] to add an additional conditional to check for the new `update_ignored_hooked_blocks_postmeta` filter so there won't be any collisions.)
Eventually, this will allow to deprecate `block_core_navigation_update_ignore_hooked_blocks_meta` (and some related functions), and remove the relevant code from the Navigation block. It also paves the way for some other future changes, such as inserting a hooked block as a Template Part block's first or last child (#60854).
Props tomjcafferkey, bernhard-reiter.
Fixes#60759.
Built from https://develop.svn.wordpress.org/trunk@58291
git-svn-id: http://core.svn.wordpress.org/trunk@57751 1a063a9b-81f0-0310-95a4-ce76da25c4cd
The Block Hooks UI relies on the `ignoredHookedBlocks` metadata when determining whether to show the toggle in the Site Editor. The problem is that for uncustomized templates we don't add this metadata.
Currently the visitor functions have a default callback of `insert_hooked_blocks` and we only add the metadata when we're writing to the database via an available filter in the template controller.
This changeset creates a new callback which both inserts the hooked blocks and adds the `ignoredHookedBlocks` metadata to the anchor block, and uses this new callback explicitly in the visitor functions that are run upon reading from the database.
We continue to set the `ignoredHookedBlocks` metadata when writing to the database, i.e. this operation happens twice. Although not ideal, this is necessary to cover the following scenarios:
* When the user adds an anchor block within the editor, we still need to add the `ignoredHookedBlocks` meta to it to prevent hooked blocks hooking on to it unexpectedly on the frontend. This is required to keep parity between the frontend and editor.
* When a user writes template data to the database directly through the API (instead of the editor), we need to again ensure we're not inserting hooked blocks unexpectedly.
It is worth noting that with this change, the first hooked block to insert relative to its anchor block will be accepted. Any additional blocks of the same type (e.g. a second `core/loginout` block) trying to hook onto the same anchor block will be ignored, irrespective of the position.
Props tomjcafferkey, bernhard-reiter, gziolo.
Fixes#59574.
Built from https://develop.svn.wordpress.org/trunk@58186
git-svn-id: http://core.svn.wordpress.org/trunk@57649 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Two `@since` PHPDoc fields, and the version argument to one `_deprecated_argument()` incorrectly stated 6.5.1 as the relevant WordPress version where a change was introduced.
This changeset fixes them by setting them to 6.5.3 instead.
Follow-up to [57919].
See #60754.
Built from https://develop.svn.wordpress.org/trunk@58042
git-svn-id: http://core.svn.wordpress.org/trunk@57508 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Currently, in blocks themes it's possible to use the ${type}_template_hierarchy filter to alter the template hierarchy. However, those filters are not taken into consideration by the Choose a pattern popup screen that appears when creating a new template in the Site Editor, causing a mismatch between the editor and the frontend.
Props aljullu, mukesh27, ntsekouras, jorgefilipecosta, gziolo.
Fixes#60846.
Built from https://develop.svn.wordpress.org/trunk@57944
git-svn-id: http://core.svn.wordpress.org/trunk@57441 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This adds an `is_dir()` check in `_get_block_templates_paths` before trying to run a `RecursiveDirectoryIterator` to avoid errors being reported in New Relic even thought the errors should be handled by a try/catch block.
Follow-up to [57215].
Props iCaleb, sean212, mukesh27, joemcgill.
Fixes#60915.
Built from https://develop.svn.wordpress.org/trunk@57928
git-svn-id: http://core.svn.wordpress.org/trunk@57429 1a063a9b-81f0-0310-95a4-ce76da25c4cd
The `$context` argument passed to filters such as `hooked_block_types`, `hooked_block`, and `hooked_block_{$hooked_block_type}` allows them to conditionally insert a hooked block. If the anchor block is contained in a template or template part, `$context` will be set to a `WP_Block_Template` object reflecting that template or part.
The aforementioned filters are applied when hooked block insertion is run upon reading a template (or part) from the DB (and before sending the template/part content with hooked blocks inserted over the REST API to the client), but also upon writing to the DB, as that's when the `ignoredHookedBlocks` metadata attribute is set.
Prior to this changeset, the `$context` passed to Block Hooks related filters in the latter case reflected the template/part that was already stored in the database (if any), which is a bug; instead, it needs to reflect the template/part that will result from the incoming `POST` network request that will trigger a database update.
Those incoming changes are encapsulated in the `$changes` argument passed to the `reset_pre_insert_template` and `reset_pre_insert_template_part` filters, respectively, and thus to the `inject_ignored_hooked_blocks_metadata_attributes` function that is hooked to them. `$changes` is of type `stdClass` and only contains the fields that need to be updated. That means that in order to create a `WP_Block_Template` object, a two-step process is needed:
- Emulate what the updated `wp_template` or `wp_template_part` post object in the database will look like by merging `$changes` on top of the existing `$post` object fetched from the DB, or from the theme's block template (part) file, if any.
- Create a `WP_Block_Template` from the resulting object.
To achieve the latter, a new helper method (`_build_block_template_object_from_post_object`) is extracted from the existing `_build_block_template_result_from_post` function. (The latter cannot be used directly as it includes a few database calls that will fail if no post object for the template has existed yet in the database.)
While somewhat complicated to implement, the overall change allows for better separation of concerns and isolation of entities. This is visible e.g. in the fact that `inject_ignored_hooked_blocks_metadata_attributes` no longer requires a `$request` argument, which is reflected by unit tests no longer needing to create a `$request` object to pass to it, thus decoupling the function from the templates endpoint controller.
Unit tests for `inject_ignored_hooked_blocks_metadata_attributes` have been moved to a new, separate file. Test coverage has been added such that now, all three relevant scenarios are covered:
- The template doesn't exist in the DB, nor is there a block theme template file for it.
- The template doesn't exist in the DB, but there is a block theme template file for it.
- The template already exists in the DB.
Those scenarios also correspond to the logical branching inside `WP_REST_Templates_Controller::prepare_item_for_database`, which is where `inject_ignored_hooked_blocks_metadata_attributes` gets its data from.
Props tomjcafferkey, bernhard-reiter, gziolo, swissspidy.
Fixes#60754.
Built from https://develop.svn.wordpress.org/trunk@57919
git-svn-id: http://core.svn.wordpress.org/trunk@57420 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This changeset adds a new `rest_pre_insert_{$this->post_type}` filter in the `WP_REST_Templates_Controller`, where it is applied to the return value of the `prepare_item_for_database` method. (This is consistent with the `WP_REST_Post_Controller`, where that filter has existed before.)
The new filter is then used to inject hooked blocks into the template (or template part) content received via the endpoint, prior to persisting it to the database.
This supersedes the previous mechanism, which was using the `rest_after_insert_{$this->post_type}` ''action'', from which it performed an additional `wp_update_post` call to update the template (part) content with the hooked blocks injected. The new technique eschews that additional call and the resulting extra revision it created, as well as a problem with regard to duplicated escaping and sanitization, which had caused some special characters to be garbled.
Props tomjcafferkey, gziolo, swissspidy, karolmanijak.
Fixes#60671.
Built from https://develop.svn.wordpress.org/trunk@57790
git-svn-id: http://core.svn.wordpress.org/trunk@57291 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Decouple hooked blocks insertion from setting the `metadata.ignoredHookedBlocks` attribute on anchor blocks, and perform the latter step upon saving a template or template part to the database. This ensures that anchor blocks that have been newly added to a template (or part) on the client side will also get `ignoredHookedBlocks` metadata set correctly, thus preserving editor/front-end parity. Hooked block insertion, on the other hand, will continue to happen upon ''reading'' a template (or part).
Props gziolo, tomjcafferkey.
Fixes#60506.
Built from https://develop.svn.wordpress.org/trunk@57627
git-svn-id: http://core.svn.wordpress.org/trunk@57128 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Using the new technique introduced in [57157] of using a `metadata.ignoredHookedBlocks` attribute in the anchor block to store information about whether or not a hooked block should be considered for injection, extend said injection to encompass ''modified'' templates and parts.
Fixes#59646.
Props gziolo, matveb.
Built from https://develop.svn.wordpress.org/trunk@57594
git-svn-id: http://core.svn.wordpress.org/trunk@57095 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This avoids redundant recursive lookups for block template paths in the same base directory by implementing a static cache. It also replaces an potentially expensive `file_exists` call in favor of doing recursive iteration of files inside a try/catch block.
Props thekt12, spacedmonkey, flixos90, mukesh27, joemcgill.
Fixes#58196.
Built from https://develop.svn.wordpress.org/trunk@57215
git-svn-id: http://core.svn.wordpress.org/trunk@56721 1a063a9b-81f0-0310-95a4-ce76da25c4cd
The recently introduced Block Hooks API exposes a filter (`hooked_block_types`) which is given a `$context` argument, among others. If the filter is called on a block that's part of a template or template part, `$context` is set to the corresponding `WP_Block_Template` object.
However, that object's `$content` property is currently ''not'' exposed to the filter. This changeset amends that shortcoming.
This is useful for callbacks that might want to detect the presence of a serialized block instance (or potentially in the future utilize the HTML API) to restrict where the block is injected (before the template is rendered).
Addressing this also achieves parity with the structure of `$context` when it represents a pattern (where pattern serialized content is present).
Props nerrad.
Fixes#59882.
Built from https://develop.svn.wordpress.org/trunk@57118
git-svn-id: http://core.svn.wordpress.org/trunk@56629 1a063a9b-81f0-0310-95a4-ce76da25c4cd
It was found that Template Part blocks were broken in the Site Editor, showing the `Template part has been deleted or is unavailable` message, due to a missing `theme` attribute.
This bug seems to have been introduced by [56896], whose goal was to only inject that attribute into the markup returned by the templates and patterns REST API endpoints but not on the frontend, in order to improve performance. It has been demonstrated locally that reverting that changeset fixes the bug.
Reverts [56896].
Props mmcalister, swisspidy, thelovelist, hellofromTonya, pbiron, Pauthake015, richtabor, nicolefurlan, huzaifaalmesbah, annezazu, kafleg, aegkr, sunitarai, shresthaaman, andraganescu, onemaggie, gziolo.
Fixes#59629.
Built from https://develop.svn.wordpress.org/trunk@56960
git-svn-id: http://core.svn.wordpress.org/trunk@56471 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Having the patterns registry inject the `theme` attribute into all Template Part blocks inside every pattern was found to negatively impact performance. It turns out that it's only required for the editor (i.e. in the REST API) but not on the frontend; there, it's instead possible to fall back to the currently active theme.
The latter change was made to the Pattern and Template Part blocks in https://github.com/WordPress/gutenberg/pull/55217, which was sync'ed to Core in [56849]. Consequently, this changeset removes `theme` attribute insertion from the frontend.
Props flixos90, gziolo, dmsnell, hellofromtonya.
Fixes#59583.
Built from https://develop.svn.wordpress.org/trunk@56896
git-svn-id: http://core.svn.wordpress.org/trunk@56407 1a063a9b-81f0-0310-95a4-ce76da25c4cd
The Template and Template Part REST API controllers have unique characteristics compared to other post type REST API controllers. They do not rely on integer IDs to reference objects; instead, they use a combination of the theme name and slug of the template, like 'twentytwentyfour//home.' Consequently, when the post types template and template part were introduced in [52062], it led to the registration of REST API endpoints for autosaves and revisions with invalid URL structures.
In this commit, we introduce new functionality to enable custom autosave and revisions endpoints to be registered at the post type level. Similar to the 'rest_controller_class' parameter, developers can now define 'revisions_rest_controller' and 'autosave_rest_controller.' This empowers developers to create custom controllers for these functionalities. Additionally, we introduce a 'late_route_registration' parameter, which proves helpful when dealing with custom URL patterns and regex pattern matching issues.
This commit registers new classes for template and template part autosave and revisions controllers, differentiating them from standard controllers in the following ways:
* The response shape now matches that of the template controller.
* Permission checks align with the template controller.
* A custom URL pattern is introduced to support slug-based identification of templates.
Furthermore, we've updated the utility function '_build_block_template_result_from_post' to support passing revision post objects. This enhancement ensures compatibility with the custom revisions controller.
Props spacedmonkey, revgeorge, andraganescu, hellofromTonya, antonvlasenko, kadamwhite, ironprogrammer, costdev, mukesh27, timothyblynjacobs, adamsilverstein.
Fixes 56922.
Built from https://develop.svn.wordpress.org/trunk@56819
git-svn-id: http://core.svn.wordpress.org/trunk@56331 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Prior to this changeset, `get_hooked_blocks` was called four times ''for every parsed block'' in each template, template part, and pattern. With this changeset applied, `get_hooked_blocks` is called only once per template, template part, or pattern.
Additionally, `get_hooked_blocks` is called only once when returning the list of all registered patterns. (The latter modification brings the implementation closer to its state prior to Block Hooks.)
Finally, when there are no registered hooked blocks or `hooked_block_types` filters, parsing, hooked block insertion, and re-serializing is skipped altogether.
Props gziolo, flixos90, joemcgill, dmsnell, spacedmonkey, hellofromtonya.
Fixes#59383.
Built from https://develop.svn.wordpress.org/trunk@56805
git-svn-id: http://core.svn.wordpress.org/trunk@56317 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Introduce a `_remove_theme_attribute_from_template_part_block()` function that can be used as a callback argument for `traverse_and_serialize_block(s)` on a parsed block tree in order to remove the `theme` attribute from all Template Part blocks found therein, and deprecate `_remove_theme_attribute_in_block_template_content()`.
Counterpart to `_inject_theme_attribute_in_template_part_block` from #59338 (which superseded `_inject_theme_attribute_in_block_template_content`, deprecated in #59452).
Props mukesh27.
Fixes#59460.
Built from https://develop.svn.wordpress.org/trunk@56724
git-svn-id: http://core.svn.wordpress.org/trunk@56236 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Move the now-deprecated function `_inject_theme_attribute_in_block_template_content` from `wp-includes/block-template-utils.php` to `wp-includes/deprecated.php`.
Follow-up [56719].
Props spacedmonkey, davidbaumwald, mukesh27.
See #59452.
Built from https://develop.svn.wordpress.org/trunk@56722
git-svn-id: http://core.svn.wordpress.org/trunk@56234 1a063a9b-81f0-0310-95a4-ce76da25c4cd
It can be replaced by passing `_inject_theme_attribute_in_template_part_block` as second argument to `traverse_and_serialize_blocks()`.
Per WordPress 6.4 Beta 1, there aren't going to be any more calls in Core to `_inject_theme_attribute_in_block_template_content()`.
Note that `_inject_theme_attribute_in_block_template_content` has always had `@access private` set in its PHPDoc.
Props gziolo.
Fixes#59452.
Built from https://develop.svn.wordpress.org/trunk@56719
git-svn-id: http://core.svn.wordpress.org/trunk@56231 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Block Hooks allow a third-party block to specify a position relative to a given block into which it will then be automatically inserted (e.g. a "Like" button block can ask to be inserted after the Post Content block, or an eCommerce shopping cart block can ask to be inserted after the Navigation block).
The underlying idea is to provide an extensibility mechanism for Block Themes, in analogy to WordPress' [https://developer.wordpress.org/plugins/hooks/ Hooks] concept that has allowed extending Classic Themes through filters and actions.
The two core tenets for Block Hooks are:
1. Insertion into the frontend should happen right after a plugin containing a hooked block is activated (i.e. the user isn't required to insert the block manually in the editor first); similarly, disabling the plugin should remove the hooked block from the frontend.
2. The user has the ultimate power to customize that automatic insertion: The hooked block is also visible in the editor, and the user's decision to persist, dismiss (i.e. remove), customize, or move it will be respected (and reflected on the frontend).
To account for both tenets, the **tradeoff** was made to limit automatic block insertion to unmodified templates (and template parts, respectively). The reason for this is that the simplest way of storing the information whether a block has been persisted to (or dismissed from) a given template (or part) is right in the template markup.
To accommodate for that tradeoff, [https://github.com/WordPress/gutenberg/pull/52969 UI controls (toggles)] are being added to increase visibility of hooked blocks, and to allow for their later insertion into templates (or parts) that already have been modified by the user.
For hooked blocks to appear both in the frontend and in the editor (see tenet number 2), they need to be inserted into both the frontend markup and the REST API (templates and patterns endpoints) equally. As a consequence, this means that automatic insertion couldn't (only) be implemented at block ''render'' stage, as for the editor, the ''serialized'' (but ''unrendered'') markup needs to be modified.
Furthermore, hooked blocks also have to be inserted into block patterns. Since practically no filters exist for the patterns registry, this has to be done in the registry's `get_registered` and `get_all_registered` methods.
Props gziolo.
Fixes#59313.
Built from https://develop.svn.wordpress.org/trunk@56649
git-svn-id: http://core.svn.wordpress.org/trunk@56161 1a063a9b-81f0-0310-95a4-ce76da25c4cd
During work on #59399, it was discovered that ''sibling'' block insertion wasn't likely going to work the way it was planned, which required devising an alternative solution. This new solution requires some changes to `traverse_and_serialize_block(s)`:
- Change the signature of the existing callback such that:
- the return value is a string that will be prepended to the result of the inner block traversal and serialization;
- the function arguments are: a ''reference'' to the current block (so it can be modified inline, which is important e.g. for `theme` attribute insertion), the parent block, and the previous block (instead of the block index and chunk index).
- Add a second callback argument to `traverse_and_serialize_block(s)`, which is called ''after'' the block is traversed and serialized.
- Its function arguments are a reference to the current block, the parent block, and the next block.
Props gziolo.
Fixes#59412. See #59313.
Built from https://develop.svn.wordpress.org/trunk@56644
git-svn-id: http://core.svn.wordpress.org/trunk@56156 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This commit enhances the performance of the get_block_theme_folders function by introducing a new method called get_block_template_folders within the WP_Theme class. Previously, this function suffered from poor performance due to repeated file lookups using file_exists. The new method implements basic caching, storing the result in the theme's cache, similar to how block themes are cached in the block_theme property (see [55236]).
Additionally, this change improves error handling by checking if a theme exists before attempting to look up the file. It also enhances test coverage.
Props spacedmonkey, thekt12, swissspidy, flixos90, costdev, mukesh27.
Fixes#58319.
Built from https://develop.svn.wordpress.org/trunk@56621
git-svn-id: http://core.svn.wordpress.org/trunk@56133 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Introduces two new functions `traverse_and_serialize_blocks` and `traverse_and_serialize_block` with the additional `$callback` argument. It is possible to pass parent block, block index, chunk index to the callback argument.
Reverts changes applied to `serialize_blocks` and `serialize_block` in #59327 with [56557].
Props ockham, mukesh27.
See #59313.
Built from https://develop.svn.wordpress.org/trunk@56620
git-svn-id: http://core.svn.wordpress.org/trunk@56132 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Rather than using `_inject_theme_attribute_in_block_template_content` to inject the `theme` attribute into all Template Part blocks found in a given file-based Block Template, introduce a new function called `_inject_theme_attribute_in_template_part_block`, and use that as second argument to `serialize_blocks()` (introduced in [56557]) in order to inject said attribute during tree traversal for serialization.
This allows for a more modular approach that will eventually be extended to implement automatic insertion of hooked blocks.
Note that we're guarding `_build_block_template_result_from_file()` (i.e. the callsite of `_inject_theme_attribute_in_template_part_block` and previously of `_inject_theme_attribute_in_block_template_content`) against regressions through additional unit test coverage added in [56562].
Props @gziolo.
Fixes#59338. See #59313.
Built from https://develop.svn.wordpress.org/trunk@56578
git-svn-id: http://core.svn.wordpress.org/trunk@56090 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Adds a new public function, `wp_get_theme_data_custom_templates` that returns the `customTemplates` defined by the active theme from `theme.json`. It also substitutes the usage of private APIs by this new
API.
Props johnbillion, audrasjb.
Fixes#59137
Built from https://develop.svn.wordpress.org/trunk@56413
git-svn-id: http://core.svn.wordpress.org/trunk@55925 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Adds a new public function, `wp_get_theme_data_template_parts` that returns the `templateParts` defined by the active theme from `theme.json`. It also substitutes the usage of private APIs by this new API.
Props felixarntz.
Fixes#59003
Built from https://develop.svn.wordpress.org/trunk@56385
git-svn-id: http://core.svn.wordpress.org/trunk@55897 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This changeset adds context to various strings:
- `'Background'` string when referring to Custom Background appearance screens
- `'Header'` string when referring to Custom Header appearance screens
- `'General'`, `'Header'` and `'Footer'` strings when referring to template part areas
Props gonzomir, SergeyBiryukov, mukesh27, costdev, ankitmaru.
Fixes#58424.
Built from https://develop.svn.wordpress.org/trunk@55881
git-svn-id: http://core.svn.wordpress.org/trunk@55393 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Pass false to the `lazy_load_term_meta` parameter given to the `WP_Query` found in `get_block_templates`. Template post types only ever have one term assigned to them. So priming term meta, does not help performance as lazy loading term meta is only useful if loading multiple terms. As `get_block_templates` is run multiple times on a block theme request, this saves processing time.
Props spacedmonkey, andraganescu, ntsekouras, oandregal, westonruter.
Fixes#58230.
Built from https://develop.svn.wordpress.org/trunk@55817
git-svn-id: http://core.svn.wordpress.org/trunk@55329 1a063a9b-81f0-0310-95a4-ce76da25c4cd