TODO List

= KEY ====================
    # Flagship
    - Regular
    ? Maybe I'll Do It
==========================

If no interest is expressed for a feature that may require a considerable
amount of effort to implement, it may get endlessly delayed. Do not be
afraid to cast your vote for the next feature to be implemented!

- Implement validation for query and for fragment
- Prevent percentages from being used in width/height attribute in images
- Maintain old attribute data in tokens (configurable?)
- Lazy update of token when validating attributes?
- Investigate how early internal structures can be accessed; this would
  prevent structures from being parsed and serialized multiple times.

FUTURE VERSIONS
---------------

3.2 release [It's All About Trust] (floating)
 # Implement untrusted, dangerous elements/attributes
    - Objects and Forms are especially wanted
 # Implement IDREF support (harder than it seems, since you cannot have
   IDREFs to non-existent IDs)
 # Frameset XHTML 1.0 and HTML 4.01 doctypes
 - Research and implement a "safe" version of the Object module

3.3 release [Error'ed]
 # Error logging for filtering/cleanup procedures
 - XSS-attempt detection--certain errors are flagged XSS-like

3.4 release [Do What I Mean, Not What I Say]
 # Additional support for poorly written HTML
    - Microsoft Word HTML cleaning (i.e. MsoNormal, but research essential!)
    - Friendly strict handling of <address> (block -> <br>)
 ? Remove redundant tags, ex. <u><u>Underlined</u></u>. Implementation notes:
    1. Analyzing which tags to remove duplicants
    2. Ensure attributes are merged into the parent tag
    3. Extend the tag exclusion system to specify whether or not the
    contents should be dropped or not (currently, there's code that could do
    something like this if it didn't drop the inner text too.)
 - Remove <span> tags that don't do anything (no attributes)
 - Remove empty inline tags<i></i>
 - Append something to duplicate IDs so they're still usable (impl. note: the
   dupe detector would also need to detect the suffix as well)
 - Externalize inline CSS to promote clean HTML, proposed by Sander Tekelenburg

4.0 release [Beyond HTML]
 # Legit token based CSS parsing (will require revamping almost every
   AttrDef class). Probably will use CSSTidy class?
 # More control over allowed CSS properties using a modularization
 # HTML 5 support
 # IRI support
 - Standardize token armor for all areas of processing
 - Convert RTL/LTR override characters to <bdo> tags, or vice versa on demand.
   Also, enable disabling of directionality

5.0 release [To XML and Beyond]
 - AllowedAttributes and ForbiddenAttributes step on the toes of XML by
   using periods; this needs to be changed.
 - Extended HTML capabilities based on namespacing and tag transforms (COMPLEX)
    - Hooks for adding custom processors to custom namespaced tags and
      attributes, offer default implementation
    - Lots of documentation and samples

Ongoing
 - More refactoring to take advantage of PHP5's facilities 
 - Refactor unit tests into lots of test methods
 - Plugins for major CMSes (COMPLEX)
    - phpBB
    - Drupal needs loving!
    - Phorum need loving!
    - more! (look for ones that use WYSIWYGs)
    - Also, maybe a FAQ for extension writers with HTML Purifier

AutoFormat
 - Smileys
 - Syntax highlighting (with GeSHi) with <pre> and possibly <?php
 - Look at http://drupal.org/project/Modules/category/63 for ideas

Optimizations
 - Reduce size of internal data-structures (esp. HTMLDefinition)
 - Research memory usage of objects versus arrays
 - Combine multiple strategies into a single, single-pass strategy
 - Get PH5P working with the latest versions of DOM, which have much more
   stringent error checking procedures. Maybe convert straight to tokens.
 - Get rid of set_include_path(). Save this for another major release.

Neat feature related
 ! Factor demo.php into a set of Printer classes, and then create a stub
   file for users here (inside the actual HTML Purifier library)
 ! Support exporting configuration, so users can easily tweak settings
   in the demo, and then copy-paste into their own setup
 - Advanced URI filtering schemes (see docs/proposal-new-directives.txt)
 - Allow scoped="scoped" attribute in <style> tags; may be troublesome
   because regular CSS has no way of uniquely identifying nodes, so we'd
   have to generate IDs
 - Explain how to use HTML Purifier in non-PHP languages / create
   a simple command line stub (or complicated?)
 - Fixes for Firefox's inability to handle COL alignment props (Bug 915)
 - Automatically add non-breaking spaces to empty table cells when
   empty-cells:show is applied to have compatibility with Internet Explorer
 - Table of Contents generation (XHTML Compiler might be reusable). May also
   be out-of-band information.
 - Full set of color keywords. Also, a way to add onto them without
   finalizing the configuration object.
 - Write a var_export and memcached DefinitionCache - Denis

Maintenance related (slightly boring)
 # CHMOD install script for PEAR installs
 ! Factor out command line parser into its own class, and unit test it
 ! Nested configuration namespaces
 - Distinguish between default settings and explicitly set settings, so
   configurations can be merged
 - Time PHPT tests

ChildDef related (very boring)
 - Abstract ChildDef_BlockQuote to work with all elements that only
   allow blocks in them, required or optional
 - Implement lenient <ruby> child validation

Wontfix
 - Non-lossy smart alternate character encoding transformations (unless
   patch provided)
 - Pretty-printing HTML: users can use Tidy on the output on entire page
 - Native content compression, whitespace stripping: use gzip if this is
   really important