[wp-trac] [WordPress Trac] #18698: Use body class in custom background callback

[WordPress Trac]

#18698: Use body class in custom background callback
-------------------------+-----------------------------
 Reporter:  GaryJ        |      Owner:
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  General      |    Version:  3.2.1
 Severity:  normal       |   Keywords:
-------------------------+-----------------------------
 When themes want to include an alternative color scheme, they might make
 use of a body class, added via a choice on a theme settings page. They can
 then do:
 {{{
 body {
     background: red;
 }
 ...
 body.grunge { // or .grunge
     background: black url(images/grunge.png);
 }
 }}}

 The problem comes when the theme also adds support for custom backgrounds.

 The lowest selector specificity score an alternative color scheme could
 have using this method would be 11 (`body.grunge`) or 10 (`.grunge`).

 The default custom callback CSS just uses `body` (specificity score of 1),
 which means even though it's an internal style sheet, and later in the
 cascade, it doesn't override the external style sheet.

 There are two options:

 1) Have all themes that want to use custom backgrounds and alternative
 color schemes define two extra functions - one that adds a body class `if
 ( get_background_image() || get_background_color() )` is true, and a
 second which duplicates all of the `_custom_background_cb()` function with
 a tweak of the output selector to include this new class, and then use
 that as the admin callback.

 2) Have WP add a 'custom-background' class within `get_body_class()` and
 use that within `_custom_background_cb()`.

 Certainly 1) is possible now without any changes to core code, but it does
 mean duplications of core code, just to change the CSS output (perhaps a
 filter on the selector, default `'body'` might work instead here?), and
 that, along with a filter to add a body class, seem redundant when it
 could be done in core. Most of the default body classes are content-
 related (type of page, template used, queried object etc.), but there are
 ones that are feature-related (admin-bar, logged-in), so custom-background
 isn't something too different.

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Ticket URL: <http://core.trac.wordpress.org/ticket/18698>
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