Polling

Paul Fernhout pdfernhout at kurtz-fernhout.com
Fri Feb 25 01:48:37 UTC 2000


agree at carltonfields.com wrote:
> Stefan Matthias Aust wrote:
> > IMHO both are
> > still not ready for developing modern GUI applications. I'd even say that
> > both system have design flaws that make it difficult if not impossible to
> > evolve the frameworks towards that goal. The polling of MVC is just one
> > example here.
> I'd be obliged if someone would explain why polling is a fatal flaw? 

* Polling uses up CPU cycles needlessly.
* To avoid using up those CPU cycles, one puts in delays.
* Delays make GUIs less responsive.
* Event quesues can be prioritized, which allows more sophisticated apps
* The OS is probably supplying events anyway -- so converting them to a
virtual mosue is another wasteful layer of extra works.
* Polling clutters up the logic of the widgets
* Polling makes it harder to stuff events into a system for automated
testing.

> Don't many other modern GUI systems, which largely follow MVC, also poll? 

I don't think they do. I think VisualWorks and VisualAge don't poll
anymore.
Anyone have a better answer?

>  I can understand why avoiding the event loop is a good thing, 
> and await seeing it truly done well.

Been waiting for two+ years...

>   But here the issue is not whose pet framework is the best, 
> but rather whether MVC or Morphic can be a useful basis 
> for preparing a serious application. 

Well put.

> Indeed, this message goes further than to say that MVC and Morphic aren't useful --
> it says that they can't even be evolved into something useful.

Well, "difficult if not impossible". What Stefan probably means is that
either would require major surgery. MVC to add events and widgets,
Morphic to remove MVC and code bloat, and add a more standard property
setting interface. (I still keep popping up halos and moving the wrong
thing when trying to use something.)

> Wasn't the preceding paragraph a highly overreaching overstatement of affairs, or should I really dump Squeak and go back to hacking Python?

Python's cool. Zope's cool. TK's cool. Squeak should learn from them.
 
> We have already seen serious applications, to wit the best IDE with which I have 
> ever worked -- all in MVC, and all reworked in Morphic.

Yes, they are nice. And yes the improvement to MVC with the pluggables
improved things.  I'm sorry though, I think lack of things like a
drop-down combo box is a major flaw. So is a simpler way to define
interfaces.  I've been using various flavors of Smalltalk for years and
I still find Squeak difficult to approach for building a meaningful GUI
(either MVC or Morphic).

> Bob Arning developed, in response to a similar challenge, 
> a simple Morphic framework for building a screens-based application 
> which looks easily extensible, and certainly evolvable into a fine application.  
> I suppose that the point can be proved or disproved by actually seeing a 
> serious application created or an effort cratered.

You got me there. I'm not sure I've seen this. But, unfortunately, there
are so many interwoven issues with using Squeak for business type apps
and making simplified GUIs, that I'll be curious how many this
addresses. Pointers to his work?

> I really think it would really be best if we avoided the hyperbole, 
> particularly when addressing ourselves to our new Squeakers.

Good point. We don't want to scare people off.

On the other hand, we must also admit Squeak is still in many ways
unapproachable for the novice (to Squeak), and still rough around the
edges. This is not going to improve until someone (ideally Squeak
Central, but it could be someone else) radically simplifies Squeak so it
can do the minimum sorts of GUI development or scripting tasks as easy
or easier than something like Delphi or Python+TK.  I've drifted into
and out of this list a couple of times and yet I still see the same
basic unapproachability of Squeak in many ways. I think critical mass is
picking up though. Morphic with some changes and additions might be
almost there. But it still isn't.

-Paul Fernhout
Kurtz-Fernhout Software 
=========================================================
Developers of custom software and educational simulations
Creators of the Garden with Insight(TM) garden simulator
http://www.kurtz-fernhout.com





More information about the Squeak-dev mailing list