[albatross-users] Random pages and application model

[Gregory Bond]

matt at pollenation.net said:
> >From debug traces I see the following sequence whenever the page is
> requested:
> 	page_enter(ctx)
> 	page_process(ctx)
> 	page_display(ctx) 

It's a bit more subtle than that.

Each albatross app has a concept of the "current page" (which is available in 
ctx.locals.__page__).  When a session is initiated, the current page is set to 
the start page specified in the application object.

When the current page is moved (either by a redirect or a set_page()), then 
page_leave() is called for the old page, and then page_enter() is called for 
the new page.

Page_display() is called to display a page (der!) and may not necessarily be 
called in conjunction with anything else (e.g. if the user hits "refresh").

When the user submits a form, then page_proces() is called.  If page_process() 
calls set_page(), then page_leave() and page_enter() will be called.  But it 
is perfectly valid for page_process() not to change the current page, in which 
case page_leave() and page_enter() will not be called.   

One subtlety is that the page_enter() may be called from within the
page_process() routine. I.e. the call graph might look like:

   application.run()
	application.process_request()
		old.page_process()
			ctx.set_page('new')
				old.page_leave()
				new.page_enter()
	application.display_response()
		new.page_display()

IIUC, the Random mixins work the same way as the non-Random versions as far as 
all this is concerned.  I hope that makes it clearer!