[wp-trac] [WordPress Trac] #34675: Introduce action hooks inside of do_meta_boxes()

[WordPress Trac]

#34675: Introduce action hooks inside of do_meta_boxes()
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 Reporter:  nikolov.tmw         |      Owner:
     Type:  feature request     |     Status:  new
 Priority:  normal              |  Milestone:  Awaiting Review
Component:  Options, Meta APIs  |    Version:
 Severity:  normal              |   Keywords:
  Focuses:  administration      |
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 Background:
 I want to add new fields to a meta box registered by a plugin. In this
 particular case, the plugin made it easy(I can filter the parameters
 passed to `add_meta_box()`), but even if it didn't, I can still modify the
 meta box in question.

 To make this more abstract, let's assume that I want to actually add
 something to a WordPress metabox( the Page Attributes one for instance ).
 In order to achieve that, I'd have to do something like this:

 {{{#!php
 <?php
 function myplugin_add_meta_boxes() {
     remove_meta_box( 'pageparentdiv', 'page', 'core' );
     add_meta_box( 'pageparentdiv', __( 'Page Attributes', 'myplugin' ),
 'myplugin_render_pageattr_meta_box', 'page', 'side', 'core' );
 }
 add_action( 'add_meta_boxes_post',  'wpse39446_add_meta_boxes' );

 function myplugin_render_pageattr_meta_box( $post ) {
     page_attributes_meta_box( $post ); ?>
     <p>Some more information/options about page attributes</p>
     <?php
 }
 }}}

 That will work just fine, until another plugin(or the theme) decides to do
 the same thing. Since I don't think there is an easy way to keep track of
 changes to meta boxes(and therefore be aware of someone else changing
 things around), it would now be a matter of which piece of code used a
 later priority(or registered it's action hook later on during execution).

 Possible solutions to that problem:

  - Create your own meta boxes in the first place. Fair point, but I
 believe that in some cases being able to add more code to an existing meta
 box would be useful(and the better approach).
  - Have core and all plugins add their own action calls. While this has
 the benefit of a better implementation(since some plugins wrap their code
 in additional div tags, that add tabs, or other visual elements), it means
 a lot of work would have to go into it(plus, it's more than likely that
 very few plugins would do that).
  - Add two new action hooks before and after the call to
 [https://github.com/WordPress/WordPress/blob/4.3-branch/wp-
 admin/includes/template.php#L1090 call_user_func($box...].

 I'm proposing the third solution as it would give reasonable flexibility,
 while reducing the chances of code collisions. It would also be easiest to
 implement, without a negative impact.

 The patch would be pretty straight-forward, but I'd like to get some
 opinions on the topic first.

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Ticket URL: <https://core.trac.wordpress.org/ticket/34675>
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