Simplified visibility control of Enclosures in Ajax requests

[Patch updated on 3/9/2011]

Problem:
-------------
The amount of boilerplate code needed to create partitions of a web page that take their
visibility setting from a controlling component in Ajax requests.

"Changing the visibility of a child component in Ajax callback method will not affect the entire
enclosure but just the child component itself. This is because only the child component is added
to the AjaxRequestTarget."

• https://cwiki.apache.org/WICKET/wickets-xhtml-tags.html

Solution:
-------------
1. InlineEnclosure tags, implemented as an attribute that can be attached to an arbitrary html tag.
Works just like a regular Enclosure, but is Ajax ready.
2. When handling Ajax requests, InlineEnclosures that are controlled by Components already in the Ajax
request target are automatically added to the Ajax request target.

Example:
------------
Below we have an ajax link: 'toggleLink' that is used to
toggle the visibility of the component 'label1'. Since the
label1 component happens to be the controlling child component
of the enclosure, the visibility of the whole enclosure is toggled
at the same time.

Html:
-------
<a href="#" wicket:id="toggleLink">Toggle visibility</a>

<div wicket:enclosure="controllingChild">
The visibility of this text is also toggled.
<div wicket:id="controllingChild">Test</div>
</div>

Here we have the 'inline' Enclosure tag:
<div wicket:enclosure="controllingChild">
Notice that no boilerplate code for this is necessary on the
Java side. The tag can be an arbitrary html tag (but cannot
simultaneously be another wicket tag, like WebMarkupContainer).
If it does not yet have a wicket id (as in this example), a
page-unique id will be generated for it (ex. inlineEnclosure-1).
The handling of the child id attribute is identical to the handling
of child id:s in traditional Wicket Enclosure tags.

On Java side we only need to introduce the child object and some kind
of control for the toggling of the visibility of the child object.
Here an ajax link is used. When user clicks the link, the visibility
of the entire Enclosure is toggled. Developer must also remember to
set the outputmarkupId=true for the label, as usual for Ajaxified code.
Nothing else is needed, the patch handles everything from here.

Java:
-------
private Label label1 = new Label("controllingChild", "Test Label 1");
private AjaxLink<Void> toggleLink;

public MinimalAjaxEnclosurePage()
{
toggleLink = new AjaxLink<Void>("toggleLink"){
@Override
public void onClick(AjaxRequestTarget target)

{ label1.setVisible(!label1.isVisible()); target.addComponent(label1); }

};
add(toggleLink);
label1.setOutputMarkupId(true);
add(label1);
}

Testing:
------------
The patch can be tested with the new unit tests in
src/test/java/org/apache/wicket/markup/html/internal

• InlineEnclosureTest has tests for rendering of Inline enclosures in various situations:
• chooses the correct child, whether or not child id is set
• reuses existing wicket:id
• works when nested with other inline Enclosures or traditional Wicket Enclosure tags
• AjaxEnclosureTest has tests for toggling visibility of Inline enclosures by toggling
  the visibility of their controllers in Ajax requests:
• only the correct child controls the enclosure, even when child id is not set
• works with nested inline enclosures
• TogglePageTests has tests for toggling visibility in ajax/non ajax situations, and where
  there are more than one targets in one ajax request

Changes to Wicket code:
-----------------------------------

• InlineEnclosureHandler:
• Recognizes inline enclosures by their attribute (wicket:enclosure) and gives them
  a session-unique id. The id is also written directly to the underlying Xml-tag.
• EnclosureResolver:
• recognizes an inline Enclosure tag and creates an InlineEnclosure instance for it
• Enclosure:
• getEnclosureParent() visibility changed to protected, to enable access from extending
  InlineEnclosure class.
• InlineEnclosure:
• implements onAfterRenderChildren, notifying child objects stored in the onComponentTagBody phase
• new method: updateVisibility(), used in Ajax calls to update the visibility of the enclosure with the
  visibility of it's controlling child object
• new method: getChildId(), used in Ajax calls to get the child's id so it can be compared to the id of components
  added to the Ajax target
• MarkupParser:
• Appended InlineEnclosureHandler to the list of filters.
• MarkupContainer
• prevented removing InlineEnclosures at the time of detach.
• WebApplication:
• newAjaxRequestTarget: Adds a new listener: AjaxEnclosureListener
• AjaxEnclosureListener (new class) (implementing AjaxRequestTarget.IListener)
• onBeforeRespond: searches the Page for those InlineEnclosures that have their
  child controllers added to Ajax Request target, and adds them to the target as well.
• Also sets these values to the found InlineEnclosures to help with ajax updates:
• setOutputMarkupPlaceholderTag=true
• setMarkupId=[id generated in InlineEnclosureHandler]
• New tests:
• src/test/java/org/apache/wicket/markup/html/internal:
• AjaxEnclosurePage_*.html / .java : test pages for AjaxEnclosureTests.java
• InlineEnclosurePage_*.html / .java : test pages for InlineEnclosureTest.java
• SimplePanel2.html / .java : test page for InlineEnclosureTest.java
• InlineEnclosurePanelPage.html / .java : test page for InlineEnclosureTest.java
• FullReloadPage.html / .java, : test pages for TogglePageTests.java
  InlineEnclosureAjaxPage.html / .java
  InlineEnclosureWithAdditionalAjaxTargetPage.html / .java
  TraditionalEnclosureAjaxPage.html /.java

• DefaultMarkupCacheKeyProvider: (Fixed a bug?)
• Added a missing dot prefixing the file-extension.
• Not directly related to the issue, but many wicket unit tests were failing without this change.

Thanks for support:
--------------------------
Martin Makundi
Igor Vaynberg
Jeremy Thomerson
Juergen Donnerstag