. added generic item editing

[roundup.git] / doc / customizing.txt

===================
Customising Roundup
===================

:Version: $Revision: 1.33 $

.. This document borrows from the ZopeBook section on ZPT. The original is at:
   http://www.zope.org/Documentation/Books/ZopeBook/current/ZPT.stx

.. contents::
   :depth: 1

What You Can Do
===============

Customisation of Roundup can take one of five forms:

1. `tracker configuration`_ file changes
2. database, or `tracker schema`_ changes
3. "definition" class `database content`_ changes
4. behavioural changes, through detectors_
5. `access controls`_

The third case is special because it takes two distinctly different forms
depending upon whether the tracker has been initialised or not. The other two
may be done at any time, before or after tracker initialisation. Yes, this
includes adding or removing properties from classes.


Trackers in a Nutshell
======================

Trackers have the following structure:

=================== ========================================================
Tracker File        Description
=================== ========================================================
config.py           Holds the basic `tracker configuration`_                 
dbinit.py           Holds the `tracker schema`_                              
interfaces.py       Defines the Web and E-Mail interfaces for the tracker    
select_db.py        Selects the database back-end for the tracker            
db/                 Holds the tracker's database                             
db/files/           Holds the tracker's upload files and messages            
detectors/          Auditors and reactors for this tracker                   
html/               Web interface templates, images and style sheets         
=================== ======================================================== 

Tracker Configuration
=====================

The config.py located in your tracker home contains the basic
configuration for the web and e-mail components of roundup's interfaces. This
file is a Python module. The configuration variables available are:

**TRACKER_HOME** - ``os.path.split(__file__)[0]``
 The tracker home directory. The above default code will automatically
 determine the tracker home for you.

**MAILHOST** - ``'localhost'``
 The SMTP mail host that roundup will use to send e-mail.

**MAIL_DOMAIN** - ``'your.tracker.email.domain.example'``
 The domain name used for email addresses.

**DATABASE** - ``os.path.join(TRACKER_HOME, 'db')``
 This is the directory that the database is going to be stored in. By default
 it is in the tracker home.

**TEMPLATES** - ``os.path.join(TRACKER_HOME, 'html')``
 This is the directory that the HTML templates reside in. By default they are
 in the tracker home.

**TRACKER_NAME** - ``'Roundup issue tracker'``
 A descriptive name for your roundup tracker. This is sent out in e-mails and
 appears in the heading of CGI pages.

**TRACKER_EMAIL** - ``'issue_tracker@%s'%MAIL_DOMAIN``
 The email address that e-mail sent to roundup should go to. Think of it as the
 tracker's personal e-mail address.

**TRACKER_WEB** - ``'http://your.tracker.url.example/'``
 The web address that the tracker is viewable at. This will be included in
 information sent to users of the tracker.

**ADMIN_EMAIL** - ``'roundup-admin@%s'%MAIL_DOMAIN``
 The email address that roundup will complain to if it runs into trouble.

**MESSAGES_TO_AUTHOR** - ``'yes'`` or``'no'``
 Send nosy messages to the author of the message.

**ADD_AUTHOR_TO_NOSY** - ``'new'``, ``'yes'`` or ``'no'``
 Does the author of a message get placed on the nosy list automatically?
 If ``'new'`` is used, then the author will only be added when a message
 creates a new issue. If ``'yes'``, then the author will be added on followups
 too. If ``'no'``, they're never added to the nosy.

**ADD_RECIPIENTS_TO_NOSY** - ``'new'``, ``'yes'`` or ``'no'``
 Do the recipients (To:, Cc:) of a message get placed on the nosy list?
 If ``'new'`` is used, then the recipients will only be added when a message
 creates a new issue. If ``'yes'``, then the recipients will be added on
 followups too. If ``'no'``, they're never added to the nosy.

**EMAIL_SIGNATURE_POSITION** - ``'top'``, ``'bottom'`` or ``'none'``
 Where to place the email signature in messages that Roundup generates.

**EMAIL_KEEP_QUOTED_TEXT** - ``'yes'`` or ``'no'``
 Keep email citations. Citations are the part of e-mail which the sender has
 quoted in their reply to previous e-mail.

**EMAIL_LEAVE_BODY_UNCHANGED** - ``'no'``
 Preserve the email body as is. Enabiling this will cause the entire message
 body to be stored, including all citations and signatures. It should be
 either ``'yes'`` or ``'no'``.

**MAIL_DEFAULT_CLASS** - ``'issue'`` or ``''``
 Default class to use in the mailgw if one isn't supplied in email
 subjects. To disable, comment out the variable below or leave it blank.

The default config.py is given below - as you
can see, the MAIL_DOMAIN must be edited before any interaction with the
tracker is attempted.::

    # roundup home is this package's directory
    TRACKER_HOME=os.path.split(__file__)[0]

    # The SMTP mail host that roundup will use to send mail
    MAILHOST = 'localhost'

    # The domain name used for email addresses.
    MAIL_DOMAIN = 'your.tracker.email.domain.example'

    # This is the directory that the database is going to be stored in
    DATABASE = os.path.join(TRACKER_HOME, 'db')

    # This is the directory that the HTML templates reside in
    TEMPLATES = os.path.join(TRACKER_HOME, 'html')

    # A descriptive name for your roundup tracker
    TRACKER_NAME = 'Roundup issue tracker'

    # The email address that mail to roundup should go to
    TRACKER_EMAIL = 'issue_tracker@%s'%MAIL_DOMAIN

    # The web address that the tracker is viewable at
    TRACKER_WEB = 'http://your.tracker.url.example/'

    # The email address that roundup will complain to if it runs into trouble
    ADMIN_EMAIL = 'roundup-admin@%s'%MAIL_DOMAIN

    # Send nosy messages to the author of the message
    MESSAGES_TO_AUTHOR = 'no'           # either 'yes' or 'no'

    # Does the author of a message get placed on the nosy list automatically?
    # If 'new' is used, then the author will only be added when a message
    # creates a new issue. If 'yes', then the author will be added on followups
    # too. If 'no', they're never added to the nosy.
    ADD_AUTHOR_TO_NOSY = 'new'          # one of 'yes', 'no', 'new'

    # Do the recipients (To:, Cc:) of a message get placed on the nosy list?
    # If 'new' is used, then the recipients will only be added when a message
    # creates a new issue. If 'yes', then the recipients will be added on followups
    # too. If 'no', they're never added to the nosy.
    ADD_RECIPIENTS_TO_NOSY = 'new'      # either 'yes', 'no', 'new'

    # Where to place the email signature
    EMAIL_SIGNATURE_POSITION = 'bottom' # one of 'top', 'bottom', 'none'

    # Keep email citations
    EMAIL_KEEP_QUOTED_TEXT = 'no'       # either 'yes' or 'no'

    # Preserve the email body as is
    EMAIL_LEAVE_BODY_UNCHANGED = 'no'   # either 'yes' or 'no'

    # Default class to use in the mailgw if one isn't supplied in email
    # subjects. To disable, comment out the variable below or leave it blank.
    # Examples:
    MAIL_DEFAULT_CLASS = 'issue'   # use "issue" class by default
    #MAIL_DEFAULT_CLASS = ''        # disable (or just comment the var out)

Tracker Schema
==============

Note: if you modify the schema, you'll most likely need to edit the
      `web interface`_ HTML template files and `detectors`_ to reflect
      your changes.

A tracker schema defines what data is stored in the tracker's database.
The
schemas shipped with Roundup turn it into a typical software bug tracker or
help desk.

XXX make sure we ship the help desk

Schemas are defined using Python code in the ``dbinit.py`` module of your
tracker. The "classic" schema looks like this::

    pri = Class(db, "priority", name=String(), order=String())
    pri.setkey("name")
    pri.create(name="critical", order="1")
    pri.create(name="urgent", order="2")
    pri.create(name="bug", order="3")
    pri.create(name="feature", order="4")
    pri.create(name="wish", order="5")

    stat = Class(db, "status", name=String(), order=String())
    stat.setkey("name")
    stat.create(name="unread", order="1")
    stat.create(name="deferred", order="2")
    stat.create(name="chatting", order="3")
    stat.create(name="need-eg", order="4")
    stat.create(name="in-progress", order="5")
    stat.create(name="testing", order="6")
    stat.create(name="done-cbb", order="7")
    stat.create(name="resolved", order="8")

    keyword = Class(db, "keyword", name=String())
    keyword.setkey("name")

    user = Class(db, "user", username=String(), password=String(),
        address=String(), realname=String(), phone=String(),
        organisation=String())
    user.setkey("username")
    user.create(username="admin", password=adminpw,
        address=config.ADMIN_EMAIL)

    msg = FileClass(db, "msg", author=Link("user"), recipients=Multilink
        ("user"), date=Date(), summary=String(), files=Multilink("file"))

    file = FileClass(db, "file", name=String(), type=String())

    issue = IssueClass(db, "issue", assignedto=Link("user"),
        topic=Multilink("keyword"), priority=Link("priority"), status=Link
        ("status"))
    issue.setkey('title')

XXX security definitions

Classes and Properties - creating a new information store
---------------------------------------------------------

In the tracker above, we've defined 7 classes of information:

  priority
      Defines the possible levels of urgency for issues.

  status
      Defines the possible states of processing the issue may be in.

  keyword
      Initially empty, will hold keywords useful for searching issues.

  user
      Initially holding the "admin" user, will eventually have an entry for all
      users using roundup.

  msg
      Initially empty, will all e-mail messages sent to or generated by
      roundup.

  file
      Initially empty, will all files attached to issues.

  issue
      Initially empty, this is where the issue information is stored.

We define the "priority" and "status" classes to allow two things: reduction in
the amount of information stored on the issue and more powerful, accurate
searching of issues by priority and status. By only requiring a link on the
issue (which is stored as a single number) we reduce the chance that someone
mis-types a priority or status - or simply makes a new one up.

Class and Items
~~~~~~~~~~~~~~~

A Class defines a particular class (or type) of data that will be stored in the
database. A class comprises one or more properties, which given the information
about the class items.
The actual data entered into the database, using class.create() are called
items. They have a special immutable property called id. We sometimes refer to
this as the itemid.

Properties
~~~~~~~~~~

A Class is comprised of one or more properties of the following types:

* String properties are for storing arbitrary-length strings.
* Password properties are for storing encoded arbitrary-length strings. The
  default encoding is defined on the roundup.password.Password class.
* Date properties store date-and-time stamps. Their values are Timestamp
  objects.
* Number properties store numeric values.
* Boolean properties store on/off, yes/no, true/false values.
* A Link property refers to a single other item selected from a specified
  class. The class is part of the property; the value is an integer, the id
  of the chosen item.
* A Multilink property refers to possibly many items in a specified class.
  The value is a list of integers.

FileClass
~~~~~~~~~

FileClasses save their "content" attribute off in a separate file from the rest
of the database. This reduces the number of large entries in the database,
which generally makes databases more efficient, and also allows us to use
command-line tools to operate on the files. They are stored in the files sub-
directory of the db directory in your tracker.

IssueClass
~~~~~~~~~~

IssueClasses automatically include the "messages", "files", "nosy", and
"superseder" properties.
The messages and files properties list the links to the messages and files
related to the issue. The nosy property is a list of links to users who wish to
be informed of changes to the issue - they get "CC'ed" e-mails when messages
are sent to or generated by the issue. The nosy reactor (in the detectors
directory) handles this action. The superceder link indicates an issue which
has superceded this one.
They also have the dynamically generated "creation", "activity" and "creator"
properties.
The value of the "creation" property is the date when an item was created, and
the value of the "activity" property is the date when any property on the item
was last edited (equivalently, these are the dates on the first and last
records in the item's journal). The "creator" property holds a link to the user
that created the issue.

setkey(property)
~~~~~~~~~~~~~~~~

Select a String property of the class to be the key property. The key property
muse be unique, and allows references to the items in the class by the content
of the key property. That is, we can refer to users by their username, e.g.
let's say that there's an issue in roundup, issue 23. There's also a user,
richard who happens to be user 2. To assign an issue to him, we could do either
of::

     roundup-admin set issue assignedto=2

or::

     roundup-admin set issue assignedto=richard

Note, the same thing can be done in the web and e-mail interfaces.

create(information)
~~~~~~~~~~~~~~~~~~~

Create an item in the database. This is generally used to create items in the
"definitional" classes like "priority" and "status".


Examples of adding to your schema
---------------------------------

TODO


Detectors - adding behaviour to your tracker
============================================
.. _detectors:

The detectors in your tracker fire before (*auditors*) and after (*reactors*)
changes to the contents of your database. They are Python modules that sit in
your tracker's ``detectors`` directory. You will have some installed by
default - have a look. You can write new detectors or modify the existing
ones. The existing detectors installed for you are:

**nosyreaction.py**
  This provides the automatic nosy list maintenance and email sending. The nosy
  reactor (``nosyreaction``) fires when new messages are added to issues.
  The nosy auditor (``updatenosy``) fires when issues are changed and figures
  what changes need to be made to the nosy list (like adding new authors etc)
**statusauditor.py**
  This provides the ``chatty`` auditor which changes the issue status from
  ``unread`` or ``closed`` to ``chatting`` if new messages appear. It also
  provides the ``presetunread`` auditor which pre-sets the status to
  ``unread`` on new items if the status isn't explicitly defined.

See the detectors section in the `design document`__ for details of the
interface for detectors.

__ design.html

Sample additional detectors that have been found useful will appear in the
``detectors`` directory of the Roundup distribution:

**newissuecopy.py**
  This detector sends an email to a team address whenever a new issue is
  created. The address is hard-coded into the detector, so edit it before you
  use it (look for the text 'team@team.host') or you'll get email errors!

  The detector code::

    from roundup import roundupdb

    def newissuecopy(db, cl, nodeid, oldvalues):
        ''' Copy a message about new issues to a team address.
        '''
        # so use all the messages in the create
        change_note = cl.generateCreateNote(nodeid)

        # send a copy to the nosy list
        for msgid in cl.get(nodeid, 'messages'):
            try:
                # note: last arg must be a list
                cl.send_message(nodeid, msgid, change_note, ['team@team.host'])
            except roundupdb.MessageSendError, message:
                raise roundupdb.DetectorError, message

    def init(db):
        db.issue.react('create', newissuecopy)


Database Content
================

Note: if you modify the content of definitional classes, you'll most likely
       need to edit the tracker `detectors`_ to reflect your changes.

Customisation of the special "definitional" classes (eg. status, priority,
resolution, ...) may be done either before or after the tracker is
initialised. The actual method of doing so is completely different in each
case though, so be careful to use the right one.

**Changing content before tracker initialisation**
    Edit the dbinit module in your tracker to alter the items created in using
    the create() methods.

**Changing content after tracker initialisation**
    Use the roundup-admin interface's create, set and retire methods to add,
    alter or remove items from the classes in question.

XXX example


Web Interface
=============

.. contents::
   :local:
   :depth: 1

The web is provided by the roundup.cgi.client module and is used by
roundup.cgi, roundup-server and ZRoundup.
In all cases, we determine which tracker is being accessed
(the first part of the URL path inside the scope of the CGI handler) and pass
control on to the tracker interfaces.Client class - which uses the Client class
from roundup.cgi.client - which handles the rest of
the access through its main() method. This means that you can do pretty much
anything you want as a web interface to your tracker.

Repurcussions of changing the tracker schema
---------------------------------------------

If you choose to change the `tracker schema`_ you will need to ensure the web
interface knows about it:

1. Index, item and search pages for the relevant classes may need to have
   properties added or removed,
2. The "page" template may require links to be changed, as might the "home"
   page's content arguments.

How requests are processed
--------------------------

The basic processing of a web request proceeds as follows:

1. figure out who we are, defaulting to the "anonymous" user
2. figure out what the request is for - we call this the "context"
3. handle any requested action (item edit, search, ...)
4. render a template, resulting in HTML output

In some situations, exceptions occur:

- HTTP Redirect  (generally raised by an action)
- SendFile       (generally raised by determine_context)
  here we serve up a FileClass "content" property
- SendStaticFile (generally raised by determine_context)
  here we serve up a file from the tracker "html" directory
- Unauthorised   (generally raised by an action)
  here the action is cancelled, the request is rendered and an error
  message is displayed indicating that permission was not
  granted for the action to take place
- NotFound       (raised wherever it needs to be)
  this exception percolates up to the CGI interface that called the client

Determining web context
-----------------------

To determine the "context" of a request, we look at the URL and the special
request variable ``:template``. The URL path after the tracker identifier
is examined. Typical URL paths look like:

1.  ``/tracker/issue``
2.  ``/tracker/issue1``
3.  ``/tracker/_file/style.css``
4.  ``/cgi-bin/roundup.cgi/tracker/file1``
5.  ``/cgi-bin/roundup.cgi/tracker/file1/kitten.png``

where the "tracker identifier" is "tracker" in the above cases. That means
we're looking at "issue", "issue1", "_file/style.css", "file1" and
"file1/kitten.png" in the cases above. The path is generally only one
entry long - longer paths are handled differently.

a. if there is no path, then we are in the "home" context.
b. if the path starts with "_file" (as in example 3,
   "/tracker/_file/style.css"), then the additional path entry,
   "style.css" specifies the filename of a static file we're to serve up
   from the tracker "html" directory. Raises a SendStaticFile
   exception.
c. if there is something in the path (as in example 1, "issue"), it identifies
   the tracker class we're to display.
d. if the path is an item designator (as in examples 2 and 4, "issue1" and
   "file1"), then we're to display a specific item.
e. if the path starts with an item designator and is longer than
   one entry (as in example 5, "file1/kitten.png"), then we're assumed
   to be handling an item of a
   FileClass, and the extra path information gives the filename
   that the client is going to label the download with (ie
   "file1/kitten.png" is nicer to download than "file1"). This
   raises a SendFile exception.

Both b. and e. stop before we bother to
determine the template we're going to use. That's because they
don't actually use templates.

The template used is specified by the ``:template`` CGI variable,
which defaults to:

- only classname suplied:          "index"
- full item designator supplied:   "item"


Performing actions in web requests
----------------------------------

When a user requests a web page, they may optionally also request for an
action to take place. As described in `how requests are processed`_, the
action is performed before the requested page is generated. Actions are
triggered by using a ``:action`` CGI variable, where the value is one of:

**login**
 Attempt to log a user in.
**logout**
 Log the user out - make them "anonymous".
**register**
 Attempt to create a new user based on the contents of the form and then log
 them in.
**edit**
 Perform an edit of an item in the database. There are some special form
 elements you may use:

 :link=designator:property and :multilink=designator:property
  The value specifies an item designator and the property on that
  item to add _this_ item to as a link or multilink.
 :note
  Create a message and attach it to the current item's
  "messages" property.
 :file
  Create a file and attach it to the current item's
  "files" property. Attach the file to the message created from
  the :note if it's supplied.
 :required=property,property,...
  The named properties are required to be filled in the form.

**new**
 Add a new item to the database. You may use the same special form elements
 as in the "edit" action.

**editCSV**
 Performs an edit of all of a class' items in one go. See also the
 *class*.csv templating method which generates the CSV data to be edited, and
 the "_generic.index" template which uses both of these features.

**search**
 Mangle some of the form variables.

 Set the form ":filter" variable based on the values of the
 filter variables - if they're set to anything other than
 "dontcare" then add them to :filter.

 Also handle the ":queryname" variable and save off the query to
 the user's query list.

Each of the actions is implemented by a corresponding *actionAction* (where
"action" is the name of the action) method on
the roundup.cgi.Client class, which also happens to be in your tracker as
interfaces.Client. So if you need to define new actions, you may add them
there (see `defining new web actions`_).

Each action also has a corresponding *actionPermission* (where
"action" is the name of the action) method which determines
whether the action is permissible given the current user. The base permission
checks are:

**login**
 Determine whether the user has permission to log in.
 Base behaviour is to check the user has "Web Access".
**logout**
 No permission checks are made.
**register**
 Determine whether the user has permission to register
 Base behaviour is to check the user has "Web Registration".
**edit**
 Determine whether the user has permission to edit this item.
 Base behaviour is to check the user can edit this class. If we're
 editing the "user" class, users are allowed to edit their own
 details. Unless it's the "roles" property, which requires the
 special Permission "Web Roles".
**new**
 Determine whether the user has permission to create (edit) this item.
 Base behaviour is to check the user can edit this class. No
 additional property checks are made. Additionally, new user items
 may be created if the user has the "Web Registration" Permission.
**editCSV**
 Determine whether the user has permission to edit this class.
 Base behaviour is to check the user can edit this class.
**search**
 Determine whether the user has permission to search this class.
 Base behaviour is to check the user can view this class.


Default templates
-----------------

Most customisation of the web view can be done by modifying the templates in
the tracker **html** directory. There are several types of files in there:

**page**
  This template defines the overall look of your tracker. When you
  view an issue, it appears inside this template. When you view an index, it
  also appears inside this template. It will have a ``tal:content`` or
  ``tal:replace`` command with the expression ``structure content`` which
  will show the issue, list of issues or whatever.
**home**
  the default page displayed when no other page is indicated by the user
**home.classlist**
  a special version of the default page that lists the classes in the tracker
**classname.item**
  displays an item of the *classname* class
**classname.index**
  displays a list of *classname* items
**classname.search**
  displays a search page for *classname* items
**_generic.index**
  used to display a list of items where there is no *classname*.index available
**_generic.help**
  used to display a "class help" page where there is no *classname*.help
**user.register**
  a special page just for the user class that renders the registration page
**style.css**
  a static file that is served up as-is

How the templates work
----------------------

Roundup's templates consist of special attributes on your template tags. These
attributes form the Template Attribute Language, or TAL. The commands are:


**tal:define="variable expression; variable expression; ..."**
   Define a new variable that is local to this tag and its contents. For
   example::

      <html tal:define="title request/description">
       <head><title tal:content="title"></title></head>
      </html>

   In the example, the variable "title" is defined as being the result of the
   expression "request/description". The tal:content command inside the <html>
   tag may then use the "title" variable.

**tal:condition="expression"**
   Only keep this tag and its contents if the expression is true. For example::

     <p tal:condition="python:request.user.hasPermission('View', 'issue')">
      Display some issue information.
     </p>

   In the example, the <p> tag and its contents are only displayed if the
   user has the View permission for issues. We consider the number zero, a
   blank string, an empty list, and the built-in variable nothing to be false
   values. Nearly every other value is true, including non-zero numbers, and
   strings with anything in them (even spaces!).

**tal:repeat="variable expression"**
   Repeat this tag and its contents for each element of the sequence that the
   expression returns, defining a new local variable and a special "repeat"
   variable for each element. For example::

     <tr tal:repeat="u user/list">
      <td tal:content="u/id"></td>
      <td tal:content="u/username"></td>
      <td tal:content="u/realname"></td>
     </tr>

   The example would iterate over the sequence of users returned by
   "user/list" and define the local variable "u" for each entry.

**tal:replace="expression"**
   Replace this tag with the result of the expression. For example::

    <span tal:replace="request/user/realname"></span>

   The example would replace the <span> tag and its contents with the user's
   realname. If the user's realname was "Bruce" then the resultant output
   would be "Bruce".

**tal:content="expression"**
   Replace the contents of this tag with the result of the expression. For
   example::

    <span tal:content="request/user/realname">user's name appears here</span>

   The example would replace the contents of the <span> tag with the user's
   realname. If the user's realname was "Bruce" then the resultant output
   would be "<span>Bruce</span>".

**tal:attributes="attribute expression; attribute expression; ..."**
   Set attributes on this tag to the results of expressions. For example::

     <a tal:attributes="href string:user${request/user/id}">My Details</a>

   In the example, the "href" attribute of the <a> tag is set to the value of
   the "string:user${request/user/id}" expression, which will be something
   like "user123".

**tal:omit-tag="expression"**
   Remove this tag (but not its contents) if the expression is true. For
   example::

      <span tal:omit-tag="python:1">Hello, world!</span>

   would result in output of::

      Hello, world!

Note that the commands on a given tag are evaulated in the order above, so
*define* comes before *condition*, and so on.

Additionally, a tag is defined, tal:block, which is removed from output. Its
content is not, but the tag itself is (so don't go using any tal:attributes
commands on it). This is useful for making arbitrary blocks of HTML
conditional or repeatable (very handy for repeating multiple table rows,
which would othewise require an illegal tag placement to effect the repeat).

The expressions you may use in the attibute values may be one of the following
three forms:

**Path Expressions** - eg. ``item/status/checklist``
   These are object attribute / item accesses. Roughly speaking, the path
   ``item/status/checklist`` is broken into parts ``item``, ``status``
   and ``checklist``. The ``item`` part is the root of the expression.
   We then look for a ``status`` attribute on ``item``, or failing that, a
   ``status`` item (as in ``item['status']``). If that
   fails, the path expression fails. When we get to the end, the object we're
   left with is evaluated to get a string - methods are called, objects are
   stringified. Path expressions may have an optional ``path:`` prefix, though
   they are the default expression type, so it's not necessary.

   XXX | components of expressions

   XXX "nothing" and "default"

**String Expressions** - eg. ``string:hello ${user/name}``
   These expressions are simple string interpolations (though they can be just
   plain strings with no interpolation if you want. The expression in the
   ``${ ... }`` is just a path expression as above.

**Python Expressions** - eg. ``python: 1+1``
   These expressions give the full power of Python. All the "root level"
   variables are available, so ``python:item.status.checklist()`` would be
   equivalent to ``item/status/checklist``, assuming that ``checklist`` is
   a method.

Information available to templates
----------------------------------

Note: this is implemented by roundup.cgi.templating.RoundupPageTemplate

The following variables are available to templates.

**context**
  The current context. This is either None, a
  `hyperdb class wrapper`_ or a `hyperdb item wrapper`_
**request**
  Includes information about the current request, including:
   - the url
   - the current index information (``filterspec``, ``filter`` args,
     ``properties``, etc) parsed out of the form. 
   - methods for easy filterspec link generation
   - *user*, the current user item as an HTMLItem instance
   - *form*
     The current CGI form information as a mapping of form argument
     name to value
**tracker**
  The current tracker
**db**
  The current database, through which db.config may be reached.
**nothing**
  This is a special variable - if an expression evaluates to this, then the
  tag (in the case of a tal:replace), its contents (in the case of
  tal:content) or some attributes (in the case of tal:attributes) will not
  appear in the the output. So for example::

    <span tal:attributes="class nothing">Hello, World!</span>

  would result in::

    <span>Hello, World!</span>

**default**
  Also a special variable - if an expression evaluates to this, then the
  existing HTML in the template will not be replaced or removed, it will
  remain. So::

    <span tal:replace="default">Hello, World!</span>

  would result in::

    <span>Hello, World!</span>

**utils**
  This variable makes available some utility functions like batching.

The context variable
~~~~~~~~~~~~~~~~~~~~

The *context* variable is one of three things based on the current context
(see `determining web context`_ for how we figure this out):

1. if we're looking at a "home" page, then it's None
2. if we're looking at a specific hyperdb class, it's a
   `hyperdb class wrapper`_.
3. if we're looking at a specific hyperdb item, it's a
   `hyperdb item wrapper`_.

If the context is not None, we can access the properties of the class or item.
The only real difference between cases 2 and 3 above are:

1. the properties may have a real value behind them, and this will appear if
   the property is displayed through ``context/property`` or
   ``context/property/field``.
2. the context's "id" property will be a false value in the second case, but
   a real, or true value in the third. Thus we can determine whether we're
   looking at a real item from the hyperdb by testing "context/id".

Hyperdb class wrapper
:::::::::::::::::::::

Note: this is implemented by the roundup.cgi.templating.HTMLClass class.

This wrapper object provides access to a hyperb class. It is used primarily
in both index view and new item views, but it's also usable anywhere else that
you wish to access information about a class, or the items of a class, when
you don't have a specific item of that class in mind.

We allow access to properties. There will be no "id" property. The value
accessed through the property will be the current value of the same name from
the CGI form.

There are several methods available on these wrapper objects:

=========== =============================================================
Method      Description
=========== =============================================================
properties  return a `hyperdb property wrapper`_ for all of this class'
            properties.
list        lists all of the active (not retired) items in the class.
csv         return the items of this class as a chunk of CSV text.
propnames   lists the names of the properties of this class.
filter      lists of items from this class, filtered and sorted
            by the current *request* filterspec/filter/sort/group args
classhelp   display a link to a javascript popup containing this class'
            "help" template.
submit      generate a submit button (and action hidden element)
renderWith  render this class with the given template.
history     returns 'New node - no history' :)
is_edit_ok  is the user allowed to Edit the current class?
is_view_ok  is the user allowed to View the current class?
=========== =============================================================

Note that if you have a property of the same name as one of the above methods,
you'll need to access it using a python "item access" expression. For example::

   python:context['list']

will access the "list" property, rather than the list method.


Hyperdb item wrapper
::::::::::::::::::::

Note: this is implemented by the roundup.cgi.templating.HTMLItem class.

This wrapper object provides access to a hyperb item.

We allow access to properties. There will be no "id" property. The value
accessed through the property will be the current value of the same name from
the CGI form.

There are several methods available on these wrapper objects:

=============== =============================================================
Method          Description
=============== =============================================================
submit          generate a submit button (and action hidden element)
journal         return the journal of the current item (**not implemented**)
history         render the journal of the current item as HTML
renderQueryForm specific to the "query" class - render the search form for
                the query
hasPermission   specific to the "user" class - determine whether the user
                has a Permission
is_edit_ok      is the user allowed to Edit the current item?
is_view_ok      is the user allowed to View the current item?
=============== =============================================================


Note that if you have a property of the same name as one of the above methods,
you'll need to access it using a python "item access" expression. For example::

   python:context['journal']

will access the "journal" property, rather than the journal method.


Hyperdb property wrapper
::::::::::::::::::::::::

Note: this is implemented by subclasses roundup.cgi.templating.HTMLProperty
class (HTMLStringProperty, HTMLNumberProperty, and so on).

This wrapper object provides access to a single property of a class. Its
value may be either:

1. if accessed through a `hyperdb item wrapper`_, then it's a value from the
   hyperdb
2. if access through a `hyperdb class wrapper`_, then it's a value from the
   CGI form


The property wrapper has some useful attributes:

=============== =============================================================
Attribute       Description
=============== =============================================================
_name           the name of the property
_value          the value of the property if any
=============== =============================================================

There are several methods available on these wrapper objects:

=========== =============================================================
Method      Description
=========== =============================================================
plain       render a "plain" representation of the property
field       render a form edit field for the property
stext       only on String properties - render the value of the
            property as StructuredText (requires the StructureText module
            to be installed separately)
multiline   only on String properties - render a multiline form edit
            field for the property
email       only on String properties - render the value of the 
            property as an obscured email address
reldate     only on Date properties - render the interval between the
            date and now
pretty      only on Interval properties - render the interval in a
            pretty format (eg. "yesterday")
menu        only on Link and Multilink properties - render a form select
            list for this property
reverse     only on Multilink properties - produce a list of the linked
            items in reverse order
=========== =============================================================

The request variable
~~~~~~~~~~~~~~~~~~~~

Note: this is implemented by the roundup.cgi.templating.HTMLRequest class.

The request variable is packed with information about the current request.

.. taken from roundup.cgi.templating.HTMLRequest docstring

=========== ================================================================
Variable    Holds
=========== ================================================================
form        the CGI form as a cgi.FieldStorage
env         the CGI environment variables
url         the current URL path for this request
base        the base URL for this tracker
user        a HTMLUser instance for this user
classname   the current classname (possibly None)
template    the current template (suffix, also possibly None)
form        the current CGI form variables in a FieldStorage
=========== ================================================================

**Index page specific variables (indexing arguments)**

=========== ================================================================
Variable    Holds
=========== ================================================================
columns     dictionary of the columns to display in an index page
show        a convenience access to columns - request/show/colname will
            be true if the columns should be displayed, false otherwise
sort        index sort column (direction, column name)
group       index grouping property (direction, column name)
filter      properties to filter the index on
filterspec  values to filter the index on
search_text text to perform a full-text search on for an index
=========== ================================================================

There are several methods available on the request variable:

=============== ============================================================
Method          Description
=============== ============================================================
description     render a description of the request - handle for the page
                title
indexargs_form  render the current index args as form elements
indexargs_url   render the current index args as a URL
base_javascript render some javascript that is used by other components of
                the templating
batch           run the current index args through a filter and return a
                list of items (see `hyperdb item wrapper`_, and
                `batching`_)
=============== ============================================================

The db variable
~~~~~~~~~~~~~~~

Note: this is implemented by the roundup.cgi.templating.HTMLDatabase class.

Allows access to all hyperdb classes as attributes of this variable. If you
want access to the "user" class, for example, you would use::

  db/user
  python:db.user

The access results in a `hyperdb class wrapper`_.


The util variable
~~~~~~~~~~~~~~~~~

Note: this is implemented by the roundup.cgi.templating.TemplatingUtils class.

=============== ============================================================
Method          Description
=============== ============================================================
Batch           return a batch object using the supplied list
=============== ============================================================

Batching
::::::::

Use Batch to turn a list of items, or item ids of a given class, into a series
of batches. Its usage is::

    python:util.Batch(sequence, size, start, end=0, orphan=0, overlap=0)

or, to get the current index batch::

    request/batch

The parameters are:

========= ==================================================================
Parameter  Usage
========= ==================================================================
sequence  a list of HTMLItems
size      how big to make the sequence.
start     where to start (0-indexed) in the sequence.
end       where to end (0-indexed) in the sequence.
orphan    if the next batch would contain less items than this
          value, then it is combined with this batch
overlap   the number of items shared between adjacent batches
========= ==================================================================

All of the parameters are assigned as attributes on the batch object. In
addition, it has several more attributes:

=============== ============================================================
Attribute       Description
=============== ============================================================
start           indicates the start index of the batch. *Note: unlike the
                argument, is a 1-based index (I know, lame)*
first           indicates the start index of the batch *as a 0-based
                index*
length          the actual number of elements in the batch
sequence_length the length of the original, unbatched, sequence.
=============== ============================================================

And several methods:

=============== ============================================================
Method          Description
=============== ============================================================
previous        returns a new Batch with the previous batch settings
next            returns a new Batch with the next batch settings
propchanged     detect if the named property changed on the current item
                when compared to the last item
=============== ============================================================

An example of batching::

 <table class="otherinfo">
  <tr><th colspan="4" class="header">Existing Keywords</th></tr>
  <tr tal:define="keywords db/keyword/list"
      tal:repeat="start python:range(0, len(keywords), 4)">
   <td tal:define="batch python:utils.Batch(keywords, 4, start)"
       tal:repeat="keyword batch" tal:content="keyword/name">keyword here</td>
  </tr>
 </table>

... which will produce a table with four columns containing the items of the
"keyword" class (well, their "name" anyway).

Displaying Properties
---------------------

Properties appear in the user interface in three contexts: in indices, in
editors, and as search arguments.
For each type of property, there are several display possibilities.
For example, in an index view, a string property may just be
printed as a plain string, but in an editor view, that property may be
displayed in an editable field.


Index Views
-----------

This is one of the class context views. It is also the default view for
classes. The template used is "*classname*.index".

Index View Specifiers
~~~~~~~~~~~~~~~~~~~~~

An index view specifier (URL fragment) looks like this (whitespace has been
added for clarity)::

     /issue?status=unread,in-progress,resolved&
            topic=security,ui&
            :group=+priority&
            :sort==activity&
            :filters=status,topic&
            :columns=title,status,fixer

The index view is determined by two parts of the specifier: the layout part and
the filter part. The layout part consists of the query parameters that begin
with colons, and it determines the way that the properties of selected items
are displayed. The filter part consists of all the other query parameters, and
it determines the criteria by which items are selected for display.
The filter part is interactively manipulated with the form widgets displayed in
the filter section. The layout part is interactively manipulated by clicking on
the column headings in the table.

The filter part selects the union of the sets of items with values matching any
specified Link properties and the intersection of the sets of items with values
matching any specified Multilink properties.

The example specifies an index of "issue" items. Only items with a "status" of
either "unread" or "in-progres" or "resolved" are displayed, and only items
with "topic" values including both "security" and "ui" are displayed. The items
are grouped by priority, arranged in ascending order; and within groups, sorted
by activity, arranged in descending order. The filter section shows filters for
the "status" and "topic" properties, and the table includes columns for the
"title", "status", and "fixer" properties.

Filtering of indexes
~~~~~~~~~~~~~~~~~~~~

TODO

Searching Views
---------------

This is one of the class context views. The template used is typically
"*classname*.search".

TODO

Item Views
----------

The basic view of a hyperdb item is provided by the "*classname*.item"
template. It generally has three sections; an "editor", a "spool" and a
"history" section.



Editor Section
~~~~~~~~~~~~~~

The editor section is used to manipulate the item - it may be a
static display if the user doesn't have permission to edit the item.

Here's an example of a basic editor template (this is the default "classic"
template issue item edit form - from the "issue.item" template)::

 <table class="form">
 <tr>
  <th nowrap>Title</th>
  <td colspan=3 tal:content="structure python:context.title.field(size=60)">title</td>
 </tr>
 
 <tr>
  <th nowrap>Priority</th>
  <td tal:content="structure context/priority/menu">priority</td>
  <th nowrap>Status</th>
  <td tal:content="structure context/status/menu">status</td>
 </tr>
 
 <tr>
  <th nowrap>Superseder</th>
  <td>
   <span tal:replace="structure python:context.superseder.field(showid=1, size=20)" />
   <span tal:replace="structure python:db.issue.classhelp('id,title')" />
   <span tal:condition="context/superseder">
    <br>View: <span tal:replace="structure python:context.superseder.link(showid=1)" />
   </span>
  </td>
  <th nowrap>Nosy List</th>
  <td>
   <span tal:replace="structure context/nosy/field" />
   <span tal:replace="structure python:db.user.classhelp('username,realname,address,phone')" />
  </td>
 </tr>
 
 <tr>
  <th nowrap>Assigned To</th>
  <td tal:content="structure context/assignedto/menu">
   assignedto menu
  </td>
  <td>&nbsp;</td>
  <td>&nbsp;</td>
 </tr>
 
 <tr>
  <th nowrap>Change Note</th>
  <td colspan=3>
   <textarea name=":note" wrap="hard" rows="5" cols="60"></textarea>
  </td>
 </tr>
 
 <tr>
  <th nowrap>File</th>
  <td colspan=3><input type="file" name=":file" size="40"></td>
 </tr>
 
 <tr>
  <td>&nbsp;</td>
  <td colspan=3 tal:content="structure context/submit">
   submit button will go here
  </td>
 </tr>
 </table>


When a change is submitted, the system automatically generates a message
describing the changed properties. As shown in the example, the editor
template can use the ":note" and ":file" fields, which are added to the
standard change note message generated by Roundup.

Spool Section
~~~~~~~~~~~~~

The spool section lists related information like the messages and files of
an issue.

TODO


History Section
~~~~~~~~~~~~~~~

The final section displayed is the history of the item - its database journal.
This is generally generated with the template::

 <tal:block tal:replace="structure context/history" />

*To be done:*

*The actual history entries of the item may be accessed for manual templating
through the "journal" method of the item*::

 <tal:block tal:repeat="entry context/journal">
  a journal entry
 </tal:block>

*where each journal entry is an HTMLJournalEntry.*

Defining new web actions
------------------------

XXX


Access Controls
===============

A set of Permissions are built in to the security module by default:

- Edit (everything)
- View (everything)

The default interfaces define:

- Web Registration
- Web Access
- Web Roles
- Email Registration
- Email Access

These are hooked into the default Roles:

- Admin (Edit everything, View everything, Web Roles)
- User (Web Access, Email Access)
- Anonymous (Web Registration, Email Registration)

And finally, the "admin" user gets the "Admin" Role, and the "anonymous" user
gets the "Anonymous" assigned when the database is initialised on installation.
The two default schemas then define:

- Edit issue, View issue (both)
- Edit file, View file (both)
- Edit msg, View msg (both)
- Edit support, View support (extended only)

and assign those Permissions to the "User" Role. New users are assigned the
Roles defined in the config file as:

- NEW_WEB_USER_ROLES
- NEW_EMAIL_USER_ROLES

You may alter the configuration variables to change the Role that new web or
email users get, for example to not give them access to the web interface if
they register through email.

You may use the ``roundup-admin`` "``security``" command to display the
current Role and Permission configuration in your tracker.

Adding a new Permission
-----------------------

When adding a new Permission, you will need to:

1. add it to your tracker's dbinit so it is created
2. enable it for the Roles that should have it (verify with
   "``roundup-admin security``")
3. add it to the relevant HTML interface templates
4. add it to the appropriate xxxPermission methods on in your tracker
   interfaces module



Examples
========

Adding a new field to a roundup schema
--------------------------------------

This example shows how to add a new constrained property (ie. a selection of
distinct values) to your tracker.

Introduction
~~~~~~~~~~~~

To make the classic schema of roundup useful as a todo tracking system
for a group of systems administrators, it needed an extra data field
per issue: a category.

This would let sysads quickly list all todos in their particular
area of interest without having to do complex queries, and without
relying on the spelling capabilities of other sysads (a losing
proposition at best).

Adding a field to the database
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the easiest part of the change. The category would just be a plain
string, nothing fancy. To change what is in the database you need to add
some lines to the ``open()`` function in ``dbinit.py``::

    category = Class(db, "category", name=String())
    category.setkey("name")

Here we are setting up a chunk of the database which we are calling
"category". It contains a string, which we are refering to as "name" for
lack of a more imaginative title. Then we are setting the key of this chunk
of the database to be that "name". This is equivalent to an index for
database types. This also means that there can only be one category with a
given name.

Adding the above lines allows us to create categories, but they're not tied
to the issues that we are going to be creating. It's just a list of categories
off on its own, which isn't much use. We need to link it in with the issues.
To do that, find the lines in the ``open()`` function in ``dbinit.py`` which
set up the "issue" class, and then add a link to the category::

    issue = IssueClass(db, "issue", ... , category=Multilink("category"), ... )

The Multilink() means that each issue can have many categories. If you were
adding something with a more one to one relationship use Link() instead.

That is all you need to do to change the schema. The rest of the effort is
fiddling around so you can actually use the new category.

Setting up security on the new objects
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

By default only the admin user can look at and change objects. This doesn't
suit us, as we want any user to be able to create new categories as
required, and obviously everyone needs to be able to view the categories of
issues for it to be useful.

We therefore need to change the security of the category objects. This is
also done in the ``open()`` function of ``dbinit.py``.

There are currently two loops which set up permissions and then assign them
to various roles. Simply add the new "category" to both lists::

    # new permissions for this schema
    for cl in 'issue', 'file', 'msg', 'user', 'category':
        db.security.addPermission(name="Edit", klass=cl,
            description="User is allowed to edit "+cl)
        db.security.addPermission(name="View", klass=cl,
            description="User is allowed to access "+cl)

    # Assign the access and edit permissions for issue, file and message
    # to regular users now
    for cl in 'issue', 'file', 'msg', 'category':
        p = db.security.getPermission('View', cl)
        db.security.addPermissionToRole('User', p)
        p = db.security.getPermission('Edit', cl)
        db.security.addPermissionToRole('User', p)

So you are in effect doing the following::

    db.security.addPermission(name="Edit", klass='category',
        description="User is allowed to edit "+'category')
    db.security.addPermission(name="View", klass='category',
        description="User is allowed to access "+'category')

which is creating two permission types; that of editing and viewing
"category" objects respectively. Then the following lines assign those new
permissions to the "User" role, so that normal users can view and edit
"category" objects::

    p = db.security.getPermission('View', 'category')
    db.security.addPermissionToRole('User', p)

    p = db.security.getPermission('Edit', 'category')
    db.security.addPermissionToRole('User', p)

This is all the work that needs to be done for the database. It will store
categories, and let users view and edit them. Now on to the interface
stuff.

Changing the web left hand frame
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We need to give the users the ability to create new categories, and the
place to put the link to this functionality is in the left hand function
bar, under the "Issues" area. The file that defines how this area looks is
``html/page``, which is what we are going to be editing next.

If you look at this file you can see that it contains a lot of "classblock"
sections which are chunks of HTML that will be included or excluded in the
output depending on whether the condition in the classblock is met. Under
the end of the classblock for issue is where we are going to add the
category code::

  <p class="classblock"
     tal:condition="python:request.user.hasPermission('View', 'category')">
   <b>Categories</b><br>
   <a tal:condition="python:request.user.hasPermission('Edit', 'category')"
      href="category?:template=item">New Category<br></a>
  </p>

The first two lines is the classblock definition, which sets up a condition
that only users who have "View" permission to the "category" object will
have this section included in their output. Next comes a plain "Categories"
header in bold. Everyone who can view categories will get that.

Next comes the link to the editing area of categories. This link will only
appear if the condition is matched: that condition being that the user has
"Edit" permissions for the "category" objects. If they do have permission
then they will get a link to another page which will let the user add new
categories.

Note that if you have permission to view but not edit categories then all
you will see is a "Categories" header with nothing underneath it. This is
obviously not very good interface design, but will do for now. I just claim
that it is so I can add more links in this section later on. However to fix
the problem you could change the condition in the classblock statement, so
that only users with "Edit" permission would see the "Categories" stuff.

Setting up a page to edit categories
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We defined code in the previous section which let users with the
appropriate permissions see a link to a page which would let them edit
conditions. Now we have to write that page.

The link was for the item template for the category object. This translates
into the system looking for a file called ``category.item`` in the ``html``
tracker directory. This is the file that we are going to write now.

First we add an id tag in a comment which doesn't affect the outcome
of the code at all but is essential for managing the changes to this
file. It is useful for debugging however, if you load a page in a
browser and look at the page source, you can see which sections come
from which files by looking for these comments::

    <!-- dollarId: category.item,v 1.3 2002/05/22 00:32:34 me Exp dollar-->

Next we need to setup up a standard HTML form, which is the whole
purpose of this file. We link to some handy javascript which sends the form
through only once. This is to stop users hitting the send button
multiple times when they are impatient and thus having the form sent
multiple times::

    <form method="POST" onSubmit="return submit_once()"
          enctype="multipart/form-data">

Next we define some code which sets up the minimum list of fields that we
require the user to enter. There will be only one field, that of "name", so
they user better put something in it otherwise the whole form is pointless::

    <input type="hidden" name=":required" value="name">

To get everything to line up properly we will put everything in a table,
and put a nice big header on it so the user has an idea what is happening::

    <table class="form">
     <tr><th class="header" colspan=2>Category</th></tr>

Next we need the actual field that the user is going to enter the new
category. The "context.name.field(size=60)" bit tells roundup to generate a
normal HTML field of size 60, and the contents of that field will be the
"name" variable of the current context (which is "category"). The upshot of
this is that when the user types something in to the form, a new category
will be created with that name::

    <tr>
     <th nowrap>Name</th>
     <td tal:content="structure python:context.name.field(size=60)">name</td>
    </tr>

Finally a submit button so that the user can submit the new category::

    <tr>
     <td>&nbsp;</td>
     <td colspan=3 tal:content="structure context/submit">
      submit button will go here
     </td>
    </tr>

So putting it all together, and closing the table and form we get::

 <!-- dollarId: category.item,v 1.3 2002/05/22 00:32:34 richard Exp dollar-->

 <form method="POST" onSubmit="return submit_once()"
       enctype="multipart/form-data">

  <input type="hidden" name=":required" value="name">

  <table class="form">
   <tr><th class="header" colspan=2>Category</th></tr>

   <tr>
    <th nowrap>Name</th>
    <td tal:content="structure python:context.name.field(size=60)">name</td>
   </tr>

   <tr>
    <td>&nbsp;</td>
    <td colspan=3 tal:content="structure context/submit">
     submit button will go here
    </td>
   </tr>
  </table>
 </form>

This is quite a lot to just ask the user one simple question, but
there is a lot of setup for basically one line (the form line) to do
its work. To add another field to "category" would involve one more line
(well maybe a few extra to get the formatting correct).

Adding the category to the issue
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We now have the ability to create issues to our hearts content, but
that is pointless unless we can assign categories to issues.  Just like
the ``html/category.item`` file was used to define how to add a new
category, the ``html/issue.item`` is used to define how a new issue is
created.

Just like ``category.issue`` this file defines a form which has a table to lay
things out. It doesn't matter where in the table we add new stuff,
it is entirely up to your sense of aesthetics::

   <th nowrap>Category</th>
   <td><span tal:replace="structure context/category/field" />
       <span tal:replace="structure db/category/classhelp" />
   </td>

First we define a nice header so that the user knows what the next section
is, then the middle line does what we are most interested in. This
``context/category/field`` gets replaced with a field which contains the
category in the current context (the current context being the new issue).

The classhelp lines generate a link (labelled "list") to a popup window
which contains the list of currently known categories.

Searching on categories
~~~~~~~~~~~~~~~~~~~~~~~

We can add categories, and create issues with categories. The next obvious
thing that we would like to be would be to search issues based on their
category, so that any one working on the web server could look at all
issues in the category "Web" for example.

If you look in the html/page file and look for the "Search Issues" you will
see that it looks something like ``<a href="issue?:template=search">Search
Issues</a>`` which shows us that when you click on "Search Issues" it will
be looking for a ``issue.search`` file to display. So that is indeed the file
that we are going to change.

If you look at this file it should be starting to seem familiar. It is a
simple HTML form using a table to define structure. You can add the new
category search code anywhere you like within that form::

    <tr>
     <th>Category:</th>
     <td>
      <select name="category">
       <option value="">don't care</option>
       <option value="">------------</option>
       <option tal:repeat="s db/category/list" tal:attributes="value s/name"
               tal:content="s/name">category to filter on</option>
      </select>
     </td>
     <td><input type="checkbox" name=":columns" value="category" checked></td>
     <td><input type="radio" name=":sort" value="category"></td>
     <td><input type="radio" name=":group" value="category"></td>
    </tr>

Most of this is straightforward to anyone who knows HTML. It is just
setting up a select list followed by a checkbox and a couple of radio
buttons. 

The ``tal:repeat`` part repeats the tag for every item in the "category"
table and setting "s" to be each category in turn.

The ``tal:attributes`` part is setting up the ``value=`` part of the option tag
to be the name part of "s" which is the current category in the loop.

The ``tal:content`` part is setting the contents of the option tag to be the
name part of "s" again. For objects more complex than category, obviously
you would put an id in the value, and the descriptive part in the content;
but for category they are the same.

Adding category to the default view
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We can now add categories, add issues with categories, and search issues
based on categories. This is everything that we need to do, however there
is some more icing that we would like. I think the category of an issue is
important enough that it should be displayed by default when listing all
the issues.

Unfortunately, this is a bit less obvious than the previous steps. The code
defining how the issues look is in ``html/issue.index``. This is a large table
with a form down the bottom for redisplaying and so forth. 

Firstly we need to add an appropriate header to the start of the table::

    <th tal:condition="request/show/category">Category</th>

The condition part of this statement is so that if the user has selected
not to see the Category column then they won't.

The rest of the table is a loop which will go through every issue that
matches the display criteria. The loop variable is "i" - which means that
every issue gets assigned to "i" in turn.

The new part of code to display the category will look like this::

    <td tal:condition="request/show/category" tal:content="i/category"></td>

The condition is the same as above: only display the condition when the
user hasn't asked for it to be hidden. The next part is to set the content
of the cell to be the category part of "i" - the current issue.

Finally we have to edit ``html/page`` again. This time to tell it that when the
user clicks on "Unnasigned Issues" or "All Issues" that the category should
be displayed. If you scroll down the page file, you can see the links with
lots of options. The option that we are interested in is the ``:columns=`` one
which tells roundup which fields of the issue to display. Simply add
"category" to that list and it all should work.


Adding in state transition control
----------------------------------

Sometimes tracker admins want to control the states that users may move issues
to.

1. add a Multilink property to the status class::

     stat = Class(db, "status", ... , transitions=Multilink('status'), ...)

   and then edit the statuses already created through the web using the
   generic class list / CSV editor.

2. add an auditor module ``checktransition.py`` in your tracker's
   ``detectors`` directory::

     def checktransition(db, cl, nodeid, newvalues):
         ''' Check that the desired transition is valid for the "status"
             property.
         '''
         if not newvalues.has_key('status'):
             return
         current = cl.get(nodeid, 'status')
         new = newvalues['status']
         if new == current:
             return
         ok = db.status.get(current, 'transitions')
         if new not in ok:
             raise ValueError, 'Status not allowed to move from "%s" to "%s"'%(
                 db.status.get(current, 'name'), db.status.get(new, 'name'))

     def init(db):
         db.issue.audit('set', checktransition)

3. in the ``issue.item`` template, change the status editing bit from::

    <th nowrap>Status</th>
    <td tal:content="structure context/status/menu">status</td>

   to::

    <th nowrap>Status</th>
    <td>
     <select tal:condition="context/id" name="status">
      <tal:block tal:define="ok context/status/transitions"
                 tal:repeat="state db/status/list">
       <option tal:condition="python:state.id in ok"
               tal:attributes="value state/id;
                               selected python:state.id == context.status.id"
               tal:content="state/name"></option>
      </tal:block>
     </select>
     <tal:block tal:condition="not:context/id"
                tal:replace="structure context/status/menu" />
    </td>

   which displays only the allowed status to transition to.


Displaying entire message contents in the issue display
-------------------------------------------------------

Alter the issue.item template section for messages to::

 <table class="messages" tal:condition="context/messages">
  <tr><th colspan=3 class="header">Messages</th></tr>
  <tal:block tal:repeat="msg context/messages/reverse">
   <tr>
    <th><a tal:attributes="href string:msg${msg/id}"
           tal:content="string:msg${msg/id}"></a></th>
    <th tal:content="string:Author: ${msg/author}">author</th>
    <th tal:content="string:Date: ${msg/date}">date</th>
   </tr>
   <tr>
    <td colspan="3" class="content">
     <pre tal:content="msg/content">content</pre>
    </td>
   </tr>
  </tal:block>
 </table>

-------------------

Back to `Table of Contents`_

.. _`Table of Contents`: index.html