The format of $wgValidSkinNames has been changed. Previously it had been `$wgValidSkinNames[key] = name;` but now it's `$wgValidSkinNames[key] = ClassNamePostfix;` In essence the code that creates a skin class has now been changed to try to create a class named "Skin{$wgValidSkinNames[$key]}". This change is because of a bug with skins that are autoloaded. Previously when you defined a skin like `$wgValidSkinNames["bluebook"] = "BlueBook";` MW would try to load SkinBluebook rather than SkinBlueBook. This worked in core because we didn't autoload skins and instead did a `require_once( "{$wgStyleDirectory}/{$wgValidSkinNames[$key]}.php" );`, because php's class system is case-insensitive SkinMonoBook always loaded fine, however this wasn't the case for extension based skins which used our case-sensitive autoloader. Keep this in mind when making autoloaded skins if you want pre-1.18 compatibility you may have to add two autoloader lines, one for SkinBlueBook and another for SkinBluebook.

Legacy skins are depreciated. The old skin system inside 'Skin' that powered the old skins CologneBlue, Nostalgia, and Standard/Classic has been dropped and replaced by a deprecated SkinLegacy system based mostly on SkinTemplate. New skins should all be SkinTemplate based, SkinLegacy only exists to support the 3 core skins that were ported, it may be eliminated from core in the near future along with the legacy skins. Note that this means a lot of methods like Skin::editThisPage() that were never meant to be used by SkinTemplate are no longer available, if you used $sk-> methods check over your skin to make sure it's not throwing errors because you were using outdated methods.

We now have a context system, if building a skin for 1.18+ please ensure that you use ->getUser(), ->getLang(), ->getRequest(), and ->getOutput(), instead of $wgUser, $wgLang, $wgRequest, and $wgOut.

The linker is now static, skins wishing to use linker methods should migrate away from calling them on $sk-> and use Linker:: properly. Note that doEditSectionLink is now explicitly part of Skin, it's no longer a Linker method, if you're using it take note of that. As a result of this and some parser changes skins can now customize the editsection link within their own skin by overloading the doEditSectionLink method. Note that if you did this before 1.18 you would pollute the cache and end up with other skins having your customizations sometimes, and your skin losing it's customization sometime. Make note of that if you override doeEditSectionLink as you may want to include a conditional to leave it alone if your skin is used in a release before 1.18.

We have two new pieces of information for skin, a relevant title and relevant user. Relevant title is used when doing things like generating tabs, special pages like Special:Movepage use it to make skins display the tabs for pages they are relevant to instead of making them suddenly disappear on the user (1.19 or later may have a more robust way of handling tabs though). Relevant user is similar, pages like Special:Contributions use it so things like the block link in the toolbar are the same as when visiting a userpage.

The specialpageattributes key is no longer needed in your skin if it's meant for 1.18+, there's better code in core now handling lang/dir for the body.

The printfooter and debughtml have been pulled out of bodytext and are now in separate printfooter and debughtml keys (I think I need to make not of that in my own skins). ((I have some issues with this change (not mine), the situation may change a little before release if I try to backport something))

The "Login / create account" link can now be split into two separate "Login" and "Create account" links by user configuration using $wgUseCombinedLoginLink. For now it defaults to the same behavior as before. Skins which have a reason to need one behavior or another (eg: turning the links into buttons and wanting to make sure they're both there) can override the useCombinedLoginLink method and return either true (combined) or false (split) to override the configuration.

A great one now. Sort of replacing content_actions we have a new content_navigation tplkey. The Vector code generating it's own hierarchical content_actions has been pulled out of vector and merged into SkinTemplate, any skin that wants to take advantage of the better organized namespace/variants/views/actions categorization of our tabs can now use content_navigation to take advantage of them. Skins using content_actions will still work, the content_actions array is created based on content_navigation now, the content_navigation arrays are annotated with information like 'primary' (vector uses this to stop collapsing of tabs into the menu on small screens) and 'redundant' for tabs like 'read' which tells the content_actions code that the tab is redundant and shouldn't be included in content_actions. Extensions which used SkinTemplateTabs and didn't add a SkinTemplateNavigation hook will stop working as the SkinTemplateNavigation hook has completely replaced SkinTemplateTabs (ok, I admit I think there's an old SkinLegacy hack that still uses SkinTemplateTabs for the tabs in legacy code). Extensions that had issues with vector's code not including replacements for the SkinTemplateBuildContentActionUrlsAfterSpecialPage and SkinTemplateContentActions hooks will be happy to know that content_actions now has equivalent replacement hooks SkinTemplateNavigation::SpecialPage and SkinTemplateNavigation::Universal which you can add. If you use these hooks in new code, and don't need pre-1.18-non-vector compat, and aren't worrying about SkinLegacy still using a SkinTemplateTabs hack you don't need to include the old hooks since content_actions is extracted from content_navigation.

There is new message fallback code in the i18n system. Many of the messages for tabs like 'move' can be overridden per-skin with messages like 'vector-action-move', 'modern-action-move', etc... If not defined they will fallback to the normal message. Vector had some message customizations before because of changes from monobook in how it handled tabs so this was added so we'd have a way to keep those without doing it in an ugly hacky way. Other skins can now include similar customizations and individual wiki can include per-skin message overrides if there are things like the edit button you want to customize the message for but have an issue where it looks fine in one skin but messes up the intuitiveness of another.

Skin QuickTemplates now have a $this->getSkin() method they can use instead of fumbling around with $this->data['skin'].

We have a new BaseTemplate class that extends QuickTemplate, it includes a number of helpers for skins and you can start to take advantage of them in a 1.18 skin by extending from BaseTemplate instead of directly from QuickTemplate. This can kill a lot of ugly boilerplate from skins like the huge boilerplate for personal_urls and content_{actions,navigation}. Links and list items for many of the common tpl key arrays we have (ie: content_{actions,navigation}, etc...) where there are arrays like personal_urls that aren't in a format these helpers can handle we have helpers like getPersonalTools that will give you an array in the right format. The search input and search button have helpers to simplify them too (I couldn't come up with a good helper for the search form opening code though). You can replace the mess of bottomscripts, reporttime, and debug trail in your skin now with a simple `$this->printTrail();`. And those remembering my footerlinks and footericons code just introduced in 1.17 will be happy to know there are helpers here to simplify the boilerplate for those. Also that horrible ugly massive boilerplate for the toolbox you have to copy into any skin, we now have a getToolbox helper that returns an array that will work with the mageListItem helper, it also has a new hook BaseTemplateToolbox that will work on that rather than have you output raw html not customized by skin. So please do start using it in skins, it would be nice to deprecate those html hooks and have extensions stop using them. ---- 1.19 is in active development so there isn't much added yet, but I do have a nice quick note on what is in there now.

Vector contains a pile of css for content styling which was basically copied from Monobook and modified slightly. That css has now been stripped out and put into three stylesheets in common/: commonElements.css: This stylesheet contains all your basic elements; Paragraphs, Links, Headers, etc... If you want anything from the common styles you'll want this at least. commonContent.css: This stylesheet contains more complex things which are contained within the content area, right now it contains things like the TOC and the frames that are wrapped around images. These are things you might not want default styles for in your skin and might want to customize in ways that having pre-existing styles could get in the way of (it's easier to override simple styles by commonElements than it is do undo the styling of the entire toc for example). commonInterface.css: This stylesheet contains some extra common stuff between MonoBook and Vector. These are tied to patterns in ids and classes for things like the usermessage, catlinks, etc... which are outside of the bodytext and the skin may decide on the ids and classes for. If you're making a skin that sticks with the MonoBook/Vector patterns of laying out and id/classing the content area you can include this stylesheet to get some of the common styles. There are a few notes on opting-in to this in your skins: - I haven't figured out how to deal with the icons for external links (the https, audio, etc... icons) yet, MonoBook and Vector use different icons so while the pattern is common the images aren't. So they aren't actually the same stylesheet wise. This may end up as a separate to include stylesheet later on. - When opting in you'll need to add a class="mw-body" somewhere into your skin to define the area where content css stylings for things like links will apply. In MonoBook this is on the same element as #bodyContent and in Vector it's #content. - To use these stylesheets include them into your ResourceLoader 'styles' array, that way it all gets combined into a single css file for your skin. -- I didn't make this a separate module because we include &skin=skinname into the /load.php call, that means that even if I make these modules they aren't reused between different skins. Hence there is no value in having them in a separate module and it's better to include them in the skin's own module where they'll be combined into a single css file. - With link styles and one or two minor changes from MonoBook to Vector the Vector difference was preferred since Vector has replaced MonoBook, MonoBook is now essentially outdated, and new skins will likely be Vector based rather than MonoBook based. If you want things to look a little more old and monobook like you may want to add some overriding css in your own styles like the rules that monobook adds in it's own css for links. - MonoBook and Vector use different bullet images for ul {}, since they're embedded images and would end up inlined in skins that might override them I opted out of including them in the elements stylesheet. If you want a list bullet image you'll have to embed one into your own stylesheet. We have an old .gif that looks like the one in MonoBook inside common, but the Vector one right now is only in vector. Though I may contemplate moving that to common.