Re: [squeak-dev] Progress bar design pattern

31 Mar 2011

      MISPRINT:
In the last part when says:
"The announcement can also know
algorithm
self doA.
       self announce: (WorkAnnoucement finished: #doA)."
shouldn't go!
Cheers,
Martin
On Thu, Mar 31, 2011 at 6:53 PM, Martin Dias tinchodias@gmail.com wrote:
...
On Thu, Mar 31, 2011 at 5:47 PM, Yoshiki Ohshima yoshiki@vpri.org wrote:
...
I don't understand the problem.  Let us say we start from the
example in the method:

'Now here''s some Real Progress'
       displayProgressAt: Sensor cursorPoint
       from: 0 to: 10
       during: [:bar |
       1 to: 10 do: [:x | bar value: x.
                       (Delay forMilliseconds: 500) wait]].

and your "algorithm" here would be:
   1 to: 10 do: [:x | "do something here"
                   (Delay forMilliseconds: 500) wait].

It is already reasonably decoupled to me, but I take that you want to
keep the "algorithm" really prestine and don't want to have "bar
value: x" call in there, and completely get rid of anything from "do
something here".  Is this the case?
There still have to have some way to tell how much percent of work
done from the "algorithm" to the progress notification mechanism.  In
the possible meta approach (which would not be that hard at all), I'd
make an instance variable for the object that represents your
algorithm state, and the algorithm assigns a value to the instance
variable, and the progress bar displayer that is running in a separate
thread looks at the variable periodically and update the screen.
However, in this senario, you would have to have an assignment to
that variable at "do something here":

   1 to: 10 do: [:x | progress := x.
                   (Delay forMilliseconds: 500) wait].

But is "progress := x" any better than "bar value: x"?
Somebody suggested announcements.  So your algorithm would look like:

   1 to: 10 do: [:x | self announce: (ProgressAnnouncement value: x).
                   (Delay forMilliseconds: 500) wait].

And a stepping morph surely does not work.  If something was started
from a do-it in workspace, next time the morph gets #step message is
after the do-it is completed.
The "bar" block could be stored in an instance variable of the
algorithm object, and your algorithm may do:

   1 to: 10 do: [:x | bar ifNotNil: [bar value: x].
                   (Delay forMilliseconds: 500) wait].

This may be just as good as it gets without complicating anything
else.
Note that your algorithm may not be a loop.  It is totally legitimate
to write:
algorithm
       self doA.
       bar value: 0.33.
       self doB.
       bar value: 0.66.
       self doC.
What you sent makes me think...
I am not convinced of this other solution, but with announcements could be:
algorithm
       self doA.
       self announce: (WorkAnnoucement finished: #doA).
       self doB.
       self announce: (WorkAnnoucement finished: #doB).
       self doC.
       self announce: (WorkAnnoucement finished: #doC).
and the specific observer subscribed to this algorithm knows what
percentage corresponds to each selector. And you could easily plug an
observer that logs to Transcript.
The announcement can also know
algorithm
   self doA.
   self announce: (WorkAnnoucement finished: #doA).

...
where doA, doB, doC are long running computation.  So, really generic
way to view the progress of something from outside without the
knowledge of where to look at and how to interpret these values are
not going to fly.
-- Yoshiki
At Thu, 31 Mar 2011 17:10:58 -0300,
Martin Dias wrote:
...
Hello
On Wed, Mar 30, 2011 at 4:24 AM, Denis Kudriashov dionisiydk@gmail.com
wrote:
...
Hello

I have idea about "meta approach" for implementation of progress

tracking of arbitrary method execution.
...
Progress tracking (progress bar stuff) is really ortogonal

functionallity for method execution. And it would be cool
...
if we have framework for describing tracking of method execution

stuff (like it progress).
...
This framework should run block of code in background and

periodically analize state of this background process
...
stack. And show this state for user. And so this framework allow

track execution of arbitrary code.
...
Analizing state can search running loops in stack for example and

show user status of loop counters.
...
I think it is not very hard to implement. But maybe this approach

can't be implemented when code jitted
...
I like the "meta approach"... but it doesn't look easy to implement for
me!
...
Have you seen something like that implemented? or some paper written?
2011/3/30 Martin Dias <tinchodias@gmail.com>

    Hello

    I have a couple of algorithms and I want to show the progress

while they run. I played with the progress bar and
...
    it's okay for my needs.

    The progress bar should be pluggable and decoupled of the

algorithms.
...
    I am writing to you to ask about good designs for my problem. I

hope I haven't expressed the problem in a too
...
    abstract way.

    The design I have in mind is a kind of observer pattern: the

serialization algorithm publishes information about
...
    the run; a specific listener implements the progress bar for

that serialization algorithm, interpreting the
...
    information published.

    Thanks,
    Martin

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