A document has been updated:
http://cocoon.zones.apache.org/daisy/documentation/685.html
Document ID: 685
Branch: main
Language: default
Name: Form Libraries (previously Form libraries)
Document Type: Document (unchanged)
Updated on: 9/5/05 1:54:47 AM
Updated by: Max Pfingsthorn
A new version has been created, state: draft
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--- <p>Here comes the documentation of the brand new form libraries!</p>
+++ <h1>Form Libraries</h1>
+++ <p class="note">This feature is only available from the repository for the
+++ Google Summer of Code (GSoC) by
+++ <a
href="https://svn.apache.org/repos/asf/cocoon/gsoc/mpfingsthorn/forms/";>Max
+++ Pfingsthorn</a> as long as it is not integrated into the current Forms
block.
+++ </p>
+++
+++ <p>It is now possible to define libraries of form definitions and bindings.
+++ Specific support for templates was intentially left out because of the
+++ frequently changing and unstructured nature of it. Other tools, such as the
JX
+++ Template Generator's import feature or a combination of the Include
Transformer
+++ and XSLT will do a better job dealing with any template formatting
needs.</p>
+++
+++ <p>One important feature of the library subsystem is inheritance. Form
widgets
+++ and bindings can inherit their contents and parameters from others. All such
+++ parent bindings/widgets will be referenced by IDs like so:</p>
+++
+++ <pre><fd:field id="myFieldID" extends="myOtherFieldID"/>
+++ </pre>
+++
+++ <p>The attribute "extends" specifies the widget or binding to inherit from.
The
+++ following is a simple example which shows how this works conceptually:</p>
+++
+++ <pre><fd:field id="parentField">
+++ <fd:label>Parent Field</fd:label>
+++ <fd:datatype base="string"/>
+++ </fd:field>
+++
+++ <fd:field id="childField" extends="parentField">
+++ <fd:selection-list>
+++ <fd:item value="1"/>
+++ <fd:item value="2">
+++ <fd:label>two</fd:label>
+++ </fd:item>
+++ <fd:item value="3"/>
+++ </fd:selection-list>
+++ </fd:field>
+++ </pre>
+++
+++ <p>The above snippet will result in the following situation:</p>
+++
+++ <pre><fd:field id="parentField">
+++ <fd:label>Parent Field</fd:label>
+++ <fd:datatype base="string"/>
+++ </fd:field>
+++
+++ <fd:field id="childField">
+++ <fd:label>Parent Field</fd:label>
+++ <fd:datatype base="string"/>
+++ <fd:selection-list>
+++ <fd:item value="1"/>
+++ <fd:item value="2">
+++ <fd:label>two</fd:label>
+++ </fd:item>
+++ <fd:item value="3"/>
+++ </fd:selection-list>
+++ </fd:field></pre>
+++
+++ <p class="note">Note that "extends" does not have to reference widgets in a
+++ library, widgets in the same context are also usable (e.g. widgets in the
same
+++ group or two top-level widgets can inherit from another).</p>
+++
+++ <h2>Form Library Inclusion</h2>
+++
+++ <p>A sample library <tt>sample.xml</tt> might look like this:</p>
+++
+++ <pre><fd:library>
+++ <fd:widgets>
+++
+++ <fd:group id="account">
+++ <fd:widgets>
+++ <fd:field id="owner">
+++ <fd:label>Account Holder</fd:label>
+++ <fd:datatype base="string"/>
+++ </fd:field>
+++ <fd:field id="balance">
+++ <fd:label>Current Balance</fd:label>
+++ <fd:datatype base="float"/>
+++ </fd:field>
+++ </fd:widgets>
+++ </fd:group>
+++
+++ </fd:widgets>
+++ </fd:library>
+++ </pre>
+++
+++ <p>This library can be easily be imported into another library or form
model by
+++ using the <tt><fd:import/></tt> statement.</p>
+++
+++ <pre><fd:form>
+++ <fd:widgets>
+++
+++ <fd:import prefix="lib" uri="sample.xml"/>
+++
+++ <fd:group id="accountWithNumber" extends="lib:account">
+++ <fd:widgets>
+++ <fd:field id="accountNo">
+++ <fd:label>Account Number</fd:label>
+++ <fd:datatype base="integer"/>
+++ </fd:field>
+++ </fd:widgets>
+++ </fd:group>
+++
+++ <fd:group id="accountWithDifferentId" extends="lib:account"/>
+++
+++ <fd:expand id="lib:account"/>
+++
+++ </fd:widgets>
+++ </fd:form>
+++ </pre>
+++
+++ <p>You can see how the value of "extends" now has a prefix which identifies
the
+++ library to use while resolving the name. The seperator is ":" and such
prefixes
+++ can also be deep, meaning reference a path in the inclusion tree if many
+++ libraries also import other libraries. In a situation where library
"common" is
+++ imported by libary "lib", then widgets in the "common" library are also
+++ accessible with the prefix "lib:common:" from a form importing only
"lib".</p>
+++
+++ <p>The above example shows the four usecases implemented in the current
library
+++ system:</p>
+++
+++ <ol>
+++ <li>Library import: Imports a specific library into the scope of a form or
+++ another library under a certain key.</li>
+++ <li>Full widget inheritance with overriding and extending information (in
the
+++ example, the "id" is overridden and a selection-list is added).</li>
+++ <li>The simple case of inheritance where only the "id" should change, say
+++ because of name clashes. While usually, the "fd:widgets" element is
required in
+++ a "fd:group", it is not if you inherit the widgets from an already existing
+++ group, so changing the "id" is really simple.</li>
+++ <li>Simply using a widget defined in a library in the current library or
form.
+++ This is achieved by the use of "fd:expand". Any occurance of "fd:expand"
will be
+++ replaced by the referenced widget.</li>
+++ </ol>
+++
+++ <p class="note">The described statements "fd:import" and "fd:expand" are
also
+++ available for bindings with exactly the same syntax and semantics, only
within
+++ the binding namespace: "fb:import" and "fb:expand".</p>
+++
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