Notice when HTTP_USER_AGENT not set

[scribu]

In [18975], yet another global was introduced: $wp_htmltag_class.

Unlike the other globals ($is_winIE, $is_opera etc.), it doesn't check if $_SERVER['HTTP_USER_AGENT'] exists, causing a notice.

[scribu]

While attempting to fix this, I noticed two things:

• $wp_htmltag_class is only used once per page load, so having it as a global doesn't help performance at all
• the beginning HTML for all the places where it's used is the same.

Hence, the _wp_admin_html_begin() function in 18966.diff​.

[azaozz]

Yes, the patch makes sense. We could probably use it for other HTML headers in the admin too. The $wp_htmltag_class was set as global to give access to plugins to modify it just like $is_IE, $is_Gecko, etc. but we can add a hook later if that's necessary.

[scribu]

Most of the pages are handled in admin-header.php.

In 18966.2.diff​, network/sites.php and upgrade.php are covered.

All the rest (install, setup-config and repair) don't seem to have the function available.

[nacin]

Per IRC, let's go with the initial patch here, 18966.diff​, but modify it so it uses boilerplate-like conditionals.

Other pages covered in 18966.2.diff are fine as well, but I don't really like the network admin conditional. Why not always use the root blog?

[scribu]

I don't like the conditional either, but was trying to stick to what was there.

[azaozz]

When using IE conditional tags we have to call do_action('admin_xml_ns'); and language_attributes(); twice, see 18966-3.patch. It's probably a tiny bit faster to check $_SERVER['HTTP_USER_AGENT'] although not as precise.

[azaozz]

In [18982]:

Use IE conditionals when adding the ie8 class, introduce _wp_admin_html_begin(), props scribu, fixes #18966