2. Как устроен Widget

Описание дано в Widget Tags for Layouts 1
Тут есть:
<*b:includable id='main' var='thiswidget'>
[insert whatever content you want here]

Each widget must have one includable with id='main'. This will usually contain most or all of the content that will display for this widget, and in many cases it will be all you need. If you make more includables with different IDs, they will not be displayed automatically. However, if you make an includable with id='new', then you can reference it in your main includable with <*b:include name='new' /> and it will display that way.

<*b:includable id='main'>
<*b:loop var='i' values='posts'>
name='post' data='i'/>



<*b:includable id='post' var='p'>
Title:


The attributes for the b:include tag are as follows:

• name: (Required) An identifier made up of letters and numbers. It must match the ID of an existing b:includable in the same widget.
• data: (Optional) An expression or peice of data to pass on to the includable section. This will become the value of the var attribute in the includable.

<*b:loop var='i' values='data:posts'>
<*h2>
<*/b:loop>

• <*b:if cond='data:post.showBacklinks'> True if the current post is set to show backlinks.
• <*b:if cond='data:blog.pageType == "item"'> True if the current page is an item page (post page).
• <*b:if cond='data:displayname != "Fred"'> True if this is not Fred's display name.
• <*b:if cond='data:post.numComments > 1'> True if the current post has more than one comment.