Here's an overview of the changes:
1) Multiple Input formats: they are complete filter configurations (what filters to use, in what order and with which settings). Input formats are admin-definable, and usage of them is role-dependant. For example, you can set it up so that regular users can only use limited HTML, while admins can free HTML without any tag limitations.
The input format can be chosen per content item (nodes, comments, blocks, ...) when you add/edit them. If only a single format is available, there is no choice, and nothing changes with before.
The default install (and the upgrade) contains a basic set of formats which should satisfy the average user's needs.
2) Filters have toggles
Because now you might want to enable a filter only on some input formats, an explicit toggle is provided by the filter system. Modules do not need to worry about it and filters that still have their own on/off switch should get rid of it.
3) Multiple filters per module
This was necessary to accomodate the next change, and it's also a logical extension of the filter system.
4) Embedded PHP is now a filter
Thanks to the multiple input formats, I was able to move the 'embedded PHP' feature from block.module, page.module and book.module into a simple filter which executes PHP code. This filter is part of filter.module, and by default there is an input format 'PHP', restricted to the administrator only, which contains this filter.
This change means that block.module now passes custom block contents through the filter system.
As well as from reducing code duplication and avoiding two type selectors for page/book nodes, you can now combine PHP code with other filters.
5) User-supplied PHP code now requires <?php ?> tags.
This is required for teasers to work with PHP code. Because PHP evaluation is now just another step in the filter process, we can't do this. Also, because teasers are generated before filtering, this would result in errors when the teaser generation would cut off a piece of PHP code.
Also, regular PHP syntax explicitly includes the <?php ?> tags for PHP files, so it makes sense to use the same convention for embedded PHP in Drupal.
6) Filter caching was added.
Benchmarking shows that even for a simple setup (basic html filtering + legacy URL rewriting), filtercache can offer speedups. Unlike the old filtercache, this uses the normal cache table.
7) Filtertips were moved from help into a hook_filter_tips(). This was required to accomodate the fact that there are multiple filters per module, and that filter settings are format dependant. Shoehorning filter tips into _help was ugly and silly. The display of the filter tips is done through the input format selector, so filter_tips_short() no longer exists.
8) A more intelligent linebreak convertor was added, which doesn't stop working if you use block-level tags and which adds <p> tags.
CHANGES
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+ Introduced tabs. First, we extended the menu system to support tabs. Next, a tab was added for every link that was (1) an administrative action other than the implicit 'view' (2) relevant to that particular page only. This is illustrated by the fact that all tabs are verbs and that clicking a page's tab leads you to a subpage of that page.
+ Flattened the administration menu. The tabs helped simplify the navigation menu as I could separate 'actions' from 'navigation'. In addition, I removed the 'administer > configuration'-menu, renamed 'blocks' to 'sidebars' which I hope is a bit more descriptive, and made a couple more changes. Earlier, we already renamed 'taxonomy' to 'categorization' and we move 'statistics' under 'logs'.
+ Grouped settings. All settings have been grouped under 'administer > settings'.
TODO
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+ Update core themes: only Xtemplate default supports tabs and even those look ugly. Need help.
+ Update contributed modules. The menu() hook changed drastically. Updating your code adhere the new menu() function should be 90% of the work. Moreover, ensure that your modue's admin links are still valid and that URLs to node get updated to the new scheme ('node/view/x' -> 'node/x').
administrators will be able to define a custom 403 page, just as they
can define 404 pages now.
This needs to be documented in the "Changes since / migrating to ..."
pages.
configurable! Menu items can be disabled, repositioned, added and
so on.
Upgrading to requires you to run update.php.
This functionality depricates some of the 'navigation modules' in the
contributions repository. Furthermore, modules can now 'suggest'
menu items and site adminstrators can choose to enable them. Modules
in the contributions repository should try to take advantage of this.
expected) and gives proper class names to the long and short tip list, so if
someone would like to reproduce the 'br' tagged version, he can do that with
some CSS styles easily. Assigned a dedicated class to the more-tips link, so it
can be differently stlyed (with a different bullet, different link color or
anyhow, as the theme designer desires).
+ Added drupal_http_request().
+ Replaced rssfeeds with OPML feed subscription list.
+ Added support for pubDate.
+ Added support for conditional gets using ETag and Last-Modified.
To do this cleanly, I reorganised some bits of system.module: there is now a generic handler available for simple variable-get/set based configuration pages. Look at filter_admin() or system_view() for example usage.
(based on the patch by Goba)
Steven Wittens
Dries Buytaert
Kjartan Mannes