David ShafferShaffer Consulting
Decorations can impact a component in many ways including adding to or
modifying the component's rendered content, changing the way in which
callbacks are processed, and intercepting component answers.
Components keep a reference to the root of (linked) list of their
decorations and have several methods related to travering this list.
We will go over this in some detail later but first lets look at an
example decoration that is already in your image:
WADecoration subclass: #WAMessageDecoration
message _ aString
html heading: message level: 3.
self renderOwnerOn: html.
FIX THE WORDING HERE: presenter vs component vs decoration
First we can see that decorations are subclasses of
WADecoration. Second we see that decorations can
renderContentOn: like components. If we just
follow the code we see that this decoration renders a heading and then
it renders the component that it is decorating (its
"owner"). If we look at
WAComponent>>addMessage: we can immediately see how to
add decorations to a component:
self addDecoration: (WAMessageDecoration new message: aString)
In reality the owner may not be a component but instead another
decoration. It is simply the "next" pointer in the linked
list. When Seaside wants to render a component it gets that
components decoration (the root of the decoration list) and renders
it. In the case of decorations they (usually) render themselves and
then render the next decoration or component in the chain. The last
component in the decoration chain is usually the component to which
all of the decorations have been added (there are exceptions to this
but it is generally true).
C. David Shaffer
Last modified: Fri Jul 22 17:28:47 EDT 2005