I have a site with multiple authors.
I would like to allow authors who create a post or a page to give rights to other authors.
For now, only administrator and editor can do that.
Is there a solution?

Yep, totally doable. By default, Co-Authors Plus defaults to ‘edit_others_posts’ as the required cap for changing co-authors. With the following code snippet in your theme’s functions.php file, you can make that cap ‘publish_posts’ instead (which authors and above usually have).

/**
 * Filter the Co-Authors Plus current_user_can_set_authors() function
 * so that users with 'publish_posts' can set Co-Authors
 *
 * @author danielbachhuber
 *
 * @see https://github.com/danielbachhuber/Co-Authors-Plus/issues/8
 * @see http://wordpress.org/support/topic/plugin-co-authors-plus-allow-authors-post-to-give-access-to-other-authors
 */
add_filter( 'coauthors_plus_edit_authors', 'db_filter_coauthors_edit_cap' );
function db_filter_coauthors_edit_cap( $cap_result ) {
	global $coauthors_plus;

	$post_type = $coauthors_plus->get_current_post_type();
	if( ! $post_type ) return false;
	
	$post_type_object = get_post_type_object( $post_type );
	return current_user_can( $post_type_object->cap->publish_posts );
}

In preparing this snippet, I also opened a couple of issues in Github:

• Allow authors to set co-authors by default – I’m not sure why we restricted it to editors and admins originally. Also, the existing filter could use cleanup.
• Don’t show search box if user doesn’t have capability to change co-authors – We should have a “locked” UI if the user doesn’t have the appropriate cap

• Sortable authors — drag and drop the order of the authors as you’d like them to appear
• Search for authors by display name so you can easily add bylines by first or last name
• Option to remove the first author when there are two or more listed
• More reliably generates the published post count for each user

Thanks to those in the forum who provided feedback and special thanks to Russell Heimlich for his contributions with sortable authors. If you feel like giving back, there are a few tickets open we’d love patches for. In particular, guest bylines would be pretty neat. I have a possible direction you can go if you’re looking for inspiration.

For our WordPress.com VIPs, this release will be available in the shared plugins directory in just a moment.

/**
* Register token search values with Post Author Box
*/
function db_add_pab_search_values( $tokens ) {
$tokens[] = '%coauthors%';
$tokens[] = '%coauthors_posts_links%';
$tokens[] = '%coauthors_firstnames%';
return $tokens;
}
add_filter( 'pab_search_values', 'db_add_pab_search_values' );
/**
* Set replacement values for specific tokens with Post Author Box
*/
function db_add_pab_replace_values( $tokens ) {
if ( !function_exists( 'coauthors' ) )
return $tokens;
$tokens['%coauthors%'] = coauthors( null, null, null, null, false );
$tokens['%coauthors_posts_links%'] = coauthors_posts_links( null, null, null, null, false );
$tokens['%coauthors_firstnames%'] = coauthors_firstnames( null, null, null, null, false );
return $tokens;
}
add_filter( 'pab_replace_values', 'db_add_pab_replace_values' );

Basically, what you need to do is register the additional tokens on the “pab_search_values” filter, and then set values for each token on the “pab_replace_values” filter.

Feel free to put this in your theme’s functions.php file, or create an MU plugin for it.

“Each plugin speaks with it’s own voice,” says Wes. Sometimes they can produced cluttered and confused experiences for your users. The framework they’ve chosen as it relates to plugins is use, patch or build.

• “Use” means they install the plugin, activate it, and it’s live. They may make minimal modifications with CSS, but it’s generally fine to go out of the box.
• “Patch” means they may make minor modifications to the codebase, through hooks or actually changing core, and then try to push the improvements they made back upstream.
• “Build” means they take ideas and inspiration from other options in the WordPress plugin directory, and roll their own plugin.

Example: Navis Slideshow

The Argo team decided to build a photo slideshow plugin that leveraged WordPress’ built in gallery functionality, and looked and worked as a standard slideshow.

Their functional starting point was the Slides for WordPress plugin. Wes downloaded and activated the plugin, and made basic presentation tweaks with CSS and Javascript. Unfortunately, there were other behavioral changes they wanted too. They thought about patching but then realized it would too much work. So they went around to rolling their own plugin.

Two improvements worth mentioning are conditionally loading images and Javascript. For the first, the problem to solve is reporters that like 60+ image photo galleries. If you load all of these images on page load, it increases your bandwidth costs and load time for end users. The solution is to reference the image URLs in a storage div, and then only load them when the user is getting close to viewing them. For the second, there’s a global variable on every page load for marking whether a WordPress gallery was included in the post. If so, the Javascript gets added to the footer.

Improvements included reducing the footprint of the plugin from 39k/895 lines to 8k/244 lines.

Example: Jiffy Posts

To make their content more engaging, Argo wanted it to make it easy for their reporters to embed rich media. Initially, this looked like Embedly or oEmbed but they didn’t want to cede control of what was embedded to the content provider.

Solution: A custom post type called Jiffy Posts. Reporters could create a new post with a title, short comment, link to the referenced media, and can include source attribution. Doing it this way, instead of having reporters embed rich media in the post, ensures there’s presentation consistency from post to post and content type to content type.

Ultimate takeaway: The decisions and opinions of plugin authors can directly impact the user experience of your website. Think about this more holistically, beyond just reviewing whether the code is clean.

The slides from the presentation are available on Slideshare and download as a PDF.