Well, after looking at that code I saw a few things that seemed
wrong.
1. If you want to render a link that starts a flow, use lambda/cc to
signal cl-cont to do its job.
2. Don't ignore the args in your render-link lambda, that's where the
continuation parameter k gets passed (details not important, unless
I'm totally mistaken!).
3. For preference, I do not use lambda's with flows. A simple widget
is always better imho, because it takes care of the continuation-
passing without having to futz around with K parameters (for the
continuation) since widgets store continuations in a slot. There's a
previous post regarding flows/continuations that has some code on
paste.lisp.org -- it may help to look at that too.
> I use the back button on the second widget, then click on the action
> link and see the second widget again.
IMO this should not be possible. The action link should have nothing
to do with the widget that was declared as part of a navigation (ie,
the 2nd widget).
This is what I tried:
1. Nav with two children 1st and 2nd.
2. 1st has a link for a with flow, yielding 3rd.
Results:
Flowing from 1st to 3rd works. Going to 2nd and using back button
brings one back to the 1st widget (whether in a state of having flowed
out to 3, or pre-flow).
The code is below, but since I'm on the old version of weblocks
(before nav and composites change) perhaps my code will be confusing,
so caveat lector.
Also, here's a short screencast showing what happens in the browser.
It's divided at the point I realized there needed to be a return from
widget 3 (back button does not work to return from continuations) and
oh, the CSS is screwed up. Nav menu is the stuff under "LaGru".
Code:
(defun init-user-session (comp)
(setf (composite-widgets comp)
(let ((main-nav (make-instance 'main-navigation :name
"LaGru")))
(init-navigation main-nav
'First (make-first)
'Second (make-widget 2))
(wrap-in-composite main-nav))))
(defun make-first ()
(let ((w (make-instance 'composite)))
(setf (composite-widgets w)
(list (make-widget 1) ; OK this works
(make-instance 'simple-widget
:render-fn
(f_
(with-html
(render-link (lambda/cc (&rest args)
(with-flow _
(yield
(make-answering-widget 3))))
"Third"))))))
w))
(defun make-answering-widget (arg)
(make-instance 'simple-widget
:render-fn
(f_
(with-html (str (format nil "This is widget ~A " arg))
(when (widget-continuation _)
(render-link (f_% (answer _))
" (return from cont) "))))))
(defun make-widget (arg)
(make-simple-message-2 (format nil "ARGE ~A" arg)))
(defun make-simple-message-2 (astr)
(make-instance 'simple-widget
:render-fn (closure (with-html (:div :class "error" (str
astr))))))
(defwidget simple-widget ()
((var :accessor get-var :initarg :var)
(render-fn :accessor render-fn :initarg :render-fn :initform
(constantly nil))))
(defmethod render-widget-body ((widget simple-widget) &rest args)
(funcall (render-fn widget) widget))
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