Synchronous animation was: [Newbies]Quick noob snippets

[Bert Freudenberg]

On 21.05.2008, at 10:33, Herbert König wrote:

> Hello Bert,
>
>
> BF> Keep in mind we are on the beginners list. I do know where this is
> BF> used, and why. But if someone asks this on the beginners list it  
> is
> BF> bad advice to give.
>
> thanks for your clear words. I'll refrain from further giving that
> advice here.
>
> I started with every Morph having its own step method for the
> animation. Then I found I needed exactly controlled synchronisation
> and ended up with one transparent Morph (subclassed the model from
> Morph instead of Object) with one central step method to animate
> everything.

Sounds great so far ...

> That's how I ended up with doOneCycle.

... but I have no idea how this comes into play here.

> Other use case: the model is rally busy with a simulation but knows
> when to draw the animation. And it needs *every* Morph redrawn.
>
> So how to solve this? Send drawOn: in the step method and send step
> from the model?

No - to mark a Morph for redraw, send #changed to it (or #invalidRect:).

> In searching I found World>>restoreMorphicDisplay (from the World
> menu) and WorldState>>displayWorldSavely
>
> Any pointers on how to control morphic display?


Well, this example does not quite fit into the Morphic logic.  
Fortunately, Squeak is malleable enough so you can still do what you  
want, as you found out already :)

Morphic normally forces you to break up the computation into small  
steps. It has a mainloop that repeatedly evaluates doOneCycle, which  
dispatches events, calls the step methods, and redraws. What you  
appear to want to do is run that loop yourself inside your simulation.  
And indeed repeatedly calling doOneCycle does exactly that. So for  
that specific use case it might actually be the best way to do it.

It makes sense if your image is customized to run exactly that one  
application, and you control what is available and what not. But it  
would interact badly with other Morphs. Imagine you wanted to run two  
copies of your simulation at the same time. That's a piece of cake  
with "well-behaved" morphs, you just duplicate it via its green halo  
handle and it works. But it would break spectacularly if you messed  
with the main loop.

- Bert -