[wp-trac] [WordPress Trac] #19342: Call to undefined function convert_to_screen when using plugins with custom meta boxes

[WordPress Trac]

#19342: Call to undefined function convert_to_screen when using plugins with custom
meta boxes
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 Reporter:  jackdewey         |       Owner:  rboren
     Type:  defect (bug)      |      Status:  closed
 Priority:  normal            |   Milestone:  3.3
Component:  Template          |     Version:  3.3
 Severity:  major             |  Resolution:  fixed
 Keywords:  has-patch commit  |
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Comment (by dd32):

 > While add_meta_box() is not one of them, some of the functions in /wp-
 admin/includes/template.php can be useful outside the admin. Are you
 saying that require_once() is bad for this specific file, or for any file
 within /wp-admin?

 In general, for any admin file, outside of an admin context is bad
 practice, you shouldn't need to include files, except for certain files
 which are not normally loaded, such as wp-admin/includes/upgrade.php

 > I ask this more specifically because we currently have a plugin that
 uses require_once() to load /wp-admin/includes/image.php because we need
 to use wp_crop_image(), and also /wp-admin/includes/upgrade.php because we
 need to use dbDelta().

 upgrade.php is a special one, since it's not generally loaded, and should
 only ever be included when needed, and only within an admin context.

 image.php is a silly one, The image manipulation functions shouldn't
 really be in admin includes IMO, and as you know, if you need to do image
 alterations outside of the admin, you currently need to include it.
 Hopefully that can change whenever media is touched again.

 That being said, You certainly shouldn't be performing image manipulation
 or database schema alterations in a front end request, it should be
 deferred until the admin is viewed, or to a cron entry or similar.. for
 the simple reason that multiple requests could cause a server overload
 very fast when you consider that many image functions in PHP require >100M
 of memory, and DB alterations can cause the same thing.

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Ticket URL: <http://core.trac.wordpress.org/ticket/19342#comment:11>
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