[Seaside] How to do the ubiquitous home button?

[Avi Bryant]

On Mon, 25 Aug 2003, Pennell, David wrote:

> How would you generalize this for bread crumb trails?

Some notes:

I chatted further just now with Julian about the two different kinds of
bread crumb trails: data structure navigation, back button simulation, and
nesting... no, three.  Three kinds of bread crumb trails:

Data structure navigation:
- For example, Yahoo, or the Inspector in Seaside.
- Already supported by WAPath
- Useful when you have a uniform display system (eg each object
knows how to display itself) and the user is allowed to move freely
through the object graph

Back button simulation:
- Useful when you have a linear, wizard-like series of steps.
- Can be done with "bookmark" objects, eg,

go
  bookmark1 := self session bookmark.
  self step1.
  bookmark2 := self session bookmark.
  self step2.
  "bookmark1 value would take us back to the beginning".

Nesting:
 - Sometimes you have a nested hierachy in your site, and you want to be
able to back out to higher levels.  The "home" button is a specific case
of this.  Usually the drilling down is modelled with #call:, and the
simple case of jumping up a single level is modelled with #answer.  So
what we need is a way of answering back multiple levels at once -
essentially, doing a non-local return.  For this we want something that
looks more like exception handling (a throw/catch metaphor?).  So,
something like this?

HomeComponent>>drillDown
  self catch: #home do: [self call: ChildComponent new].

SomeChildOfTheChildComponent>>home
  self throw: #home

That would "unwind" any of the component #calls that had been done to get
to that point, until it found the catch for #home.

A simpler way to do the same thing might be something like

self returnTo: HomeComponent

which would unwind until it found something of the appropiate class...

Just throwing out ideas, here.