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-<!doctype article PUBLIC "-//Davenport//DTD DocBook V3.0//EN" [
-<!entity Evolution "<application>Evolution</application>">
-<!entity ETable "<classname>ETable</classname>">
-<!entity ETableModel "<classname>ETableModel</classname>">
-<!entity ETableSimple "<classname>ETableSimple</classname>">
-<!entity ETableHeader "<classname>ETableHeader</classname>">
-<!entity ETableSpecification "<classname>ETableSpecification</classname>">
-<!entity ETableCol "<classname>ETableCol</classname>">
-]>
-
-<article class="whitepaper" id="e-table">
-
- <artheader>
- <title>The ETable Widget</title>
-
- <authorgroup>
- <author>
- <firstname>Chris</firstname>
- <surname>Lahey</surname>
- <affiliation>
- <address>
- <email>clahey@helixcode.com</email>
- </address>
- </affiliation>
- </author>
- <author>
- <firstname>Miguel</firstname>
- <surname>de Icaza</surname>
- <affiliation>
- <address>
- <email>miguel@helixcode.com</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <copyright>
- <year>2000</year>
- <holder>Helix Code, Inc.</holder>
- </copyright>
-
- </artheader>
-
- <sect1 id="introduction">
- <title>Introduction</title>
-
- <para>
- &ETable; is a table widget on steroids. It is intended to provide
- all the table functionality needed throughout &Evolution;, and
- hopefully be general purpose enough to be used in other projects.
- </para>
-
- <para>
- &ETable; provides a lot of interactive control over the data in the
- table. Without any work from the programmer, &ETable; provides
- rearrangeable columns and editable data. When finished, &ETable; will
- also provide, again with no programmer intervention, easy interactive
- sorting and grouping.
- </para>
-
- <para>
- &ETable; gives you a great deal of functionality, flexibility, and
- power. Most of this power is internal to the widget, but some of
- the flexibility requires a bit of work by the programmer.
- However, once you learn it, &ETable; is not very hard at all to
- use.
- </para>
-
- <para>
- &ETable;'s power comes from the fact that it is fully
- model/view/controller based. Various models are involved into
- the process of rendering the information, and various views are
- provided. The programmer has a wide range of options: from the
- most finely hand-tuned table to a generic all-encompasing widget
- that takes over most of tasks. It is up to the programmer: he
- can use the simple to use &ETable; widget that takes care of
- everything in a generic way, or he can use the various
- components to roll his own tabular display.
- </para>
-
- <para>
- &ETable; ships with a standard set of information renderers:
- strings, bitmaps, toggle-buttons, check-boxes, and multi-line
- strings. But the programmer can write and implement his own
- renderer for his information. This means that by default
- &ETable; provides the basic display facilities that programmers
- required, but they offer the programmer a complete freedom to
- incorporate new cell renderers.
- </para>
-
- </sect1>
-
- <sect1 id="model">
- <title>ETableModel</title>
-
- <para>
- The data back end for the &ETable; is an &ETableModel;. The
- &ETableModel is an abstract interface that acts as the
- information repository for the various &ETable components.
- </para>
-
- <para>
- To use &ETable; you have to create a subclass of the abstract
- &ETableModel; class. However, to save you the work of defining
- a new <classname>GtkClass</classname> every time you use
- &ETable, there is a predefined subclass of &ETableModel; called
- &ETableSimple; which simply takes a list of function callbacks
- to perform the various operations.
- </para>
-
- </sect1>
-
- <sect1 id="columns">
- <title>Columns</title>
-
- <para>
- There are two different meanings to the word "column". The first
- is the model column (defined by the &ETableCol: object). A model
- column describes how it maps to the column in the &ETableModel;
- as well as containing information about its properties (name,
- resizability, resize dimensions, and a renderer for this
- specific columns).
- </para>
-
- <para>
- &ETable; distinguishes between a model column index, and a view
- column index. The former reflects the column in which the data
- is stored in the &ETableModel; The later represents the actual
- location at which the column is being displayed in the screen.
- </para>
-
- <para>
- Each view column index corresponds to a specific model column,
- though a model column may have any number of view columns
- associated with it (including zero). For example the same
- column might be rendered twice, or the data from one column
- could be used to display different bits of information
- </para>
-
- <para>
- The view column does not necessarily depend on only one model
- column. In some cases, the view column renderer can be given a
- reference to another model column to get extra information about
- its display. For example, a mail program could display deleted
- messages with a line through them by creating a model column
- with no corresponding view column that told whether or not the
- message is deleted, and then having the text column
- strikethrough the display if the invisible column had a value
- corresponding to "deleted".
- </para>
-
- <para>
- The view column also specifies a few other pieces of
- information. One piece of information is the renderer. &ETable;
- provides a number of renderers to choose from, or you can write
- your own. Currently, there are renderers for text, image sets,
- and checkboxes.
- </para>
-
- <para>
- The view column also includes information about the header.
- There are two types of headers: text, and pixbuf. The first
- allows you to specify a string which is rendered in the header.
- The second allows you to specify an image to copy into the
- header.
- </para>
- </sect1>
-
- <sect1 id="header">
- <title>Header</title>
-
- <para>
- The &ETableHeader; represents the header information for the
- table. The &ETableHeader; is used in two different ways. The
- first is the in the <structfield>full_header</structfield>
- element of an &ETable;. This is the list of possible columns in
- the view. You add each of your columns to this &ETableHeader;
- and then pass it into the &ETable;.
- </para>
-
- <para>
- The second use is completely internal. &ETable; uses another
- &ETableHeader; to store the actual displayed columns. Many of
- the &ETableHeader; functions are for this purpose. The only
- functions that users of the library should need to use are
- <function>e_table_header_new</function> and
- <function>e_table_header_add_col</function>.
- </para>
- </sect1>
-
- <sect1 id="layout">
- <title>Layout Specification</title>
-
- <para>
- &ETable; uses an &ETableSpecification; to layout the columns of
- the widget. The &ETableSpecification; is specified as XML data
- passed into the &ETable; as a string.
- </para>
-
- <para>
- The most powerful part of the &ETableSpecification; is that when
- finished, &ETable; will allow you to get a copy of an
- &ETableSpecification; that describes the current view of the
- tree. This allows the developer to save the current view so that
- next time the user opens this table, they find it in exactly the
- state that they left it.
- </para>
-
- <para>
- The XML specification allows for a number of things. First, it
- allows you to pick a set of default columns to be shown. Thus,
- even if you had hundreds of pieces of data, you could choose to
- only display a few that fit on the screen by default.
- </para>
-
- <para>
- The second major thing that the &ETableSpecification; allows you
- to specify is the column grouping and sorting. &ETable; has a
- powerful mechanism for allowing the user to choose columns to
- group by, thus allowing multiple columns of sorting, as well as
- visual grouping of similar elements and interactive selection of
- what data to display.
- </para>
-
- <para>
- The grouping in &ETableSpecification; is specified as a
- hierarchy of columns to group by. Each level of the hierarchy
- lets you sort by a particular column, either ascending or
- descending. All levels except the last cause the canvas to group
- by the given column.
- </para>
-
- <para>
- An example &ETableSpecification; follows.
- </para>
-
- <programlisting>
- &lt;ETableSpecification&gt;
- &lt;columns-shown frozen_columns="2"&gt;
- &lt;column&gt; 0 &lt;/column&gt;
- &lt;column&gt; 1 &lt;/column&gt;
- &lt;column&gt; 2 &lt;/column&gt;
- &lt;column&gt; 3 &lt;/column&gt;
- &lt;column&gt; 4 &lt;/column&gt;
- &lt;/columns-shown&gt;
- &lt;grouping&gt;
- &lt;group column="3" ascending="1"&gt;
- &lt;group column="4" ascending="0"&gt;
- &lt;leaf column="2" ascending="1"/&gt;
- &lt;/group&gt;
- &lt;/group&gt;
- &lt;/grouping&gt;
- &lt;/ETableSpecification&gt;
- </programlisting>
-
- <para>
- This example has 5 columns which are initially in order. It has
- 2 levels of grouping. The first is grouped by the 4th column
- (all indexes are 0 based) and sorts those groups in ascending
- order. Inside those groups, the data is grouped by the fifth
- column and sorted in descending order of the fifth column.
- Finally, the data in those groups is sorted by the third column
- in ascending order. Due to the "frozen_columns" attribute on the
- columns-shown element, the user will not be
- able to rearrange the first two columns. They will always be the
- first two.
- </para>
- </sect1>
-
- <sect1 id="conclusion">
- <title>Conclusion</title>
-
- <para>
- All in all, &ETable; is a very powerful widget. Once you learn
- to use it, you have access to a vast amount of power requiring a
- comparatively small amount of work.
- </para>
- </sect1>
-</article>