[Squeakland] Making a Copy of an eToy from a script and using the mouse pointer to activate an eToy script

[Scott Wallace]

On Nov 13, 2006, at 10:18 AM, Offray Vladimir Luna Cárdenas wrote:

> Hi Scott :),
>
> Thanks for your help again. What you're providing me is pretty  
> close to what me and my students are looking for. Because my lack  
> of knowledge of the Smalltalk code I'm trying to understand the  
> textual script. I see that in that script, there is not switch from  
> tile mode to code/text mode, only the last one is enabled. There is  
> some special way to add this scripts? If I try, for example to use  
> the visor of a Star I always can switch from tile to code modes,  
> but coming back to tile, always makes the changes in text mode to  
> get loosed  (not saved).


Hi, Offray!

Once you have typed in textual code for a script, you cannot return  
to tile mode without losing the textual code you typed.  There is no  
automatic translation from user-entered textual code back into etoy  
tiles.  Indeed, the constructs supported by etoy tiles represent but  
a tiny fraction of what can be expressed in textual Smalltalk code.

Some people are quite disappointed, and even offended, when they  
first learn this brutal fact.  But "etoys" is a tile-scripting  
system, with severe and intentional limits to vocabulary, sentence  
structure, expression structure, and control structures.  The textual- 
scripting alternative provides nothing more than a "keyhole" which  
allows some people to "escape" from tiles, into textual Smalltalk  
programming, specifically to program things that cannot be expressed  
with tiles.

Because reverting from a textually-entered script back to tiles is  
destructive, the user is presented with a warning if he tries to do  
it -- a stern warning that any code he has manually entered via the  
keyboard for this script will be lost.

The reason why this warning was not presented when you tried to click  
the text/tiles checkbox of the #chooseMessageTarget script to revert  
to tiles is because of a bug that appears when you attempt to toggle  
a textually-coded script which has never had any non-empty tile  
code.  (I have a fix for that bug, which I'm about to publish to the  
Squeakland alpha update stream.)

However, even if had been allowed, you would not have wanted to  
revert that script to its last-known tile form, because in so doing  
you would have lost the textual code which is the whole point of the  
script.


> chooseMessageTarget "the name of the script"
>
>  "Choose a player as target for a message" "<- comment with the  
> explanation"
>  | aMorph | "<- some kind of local variable"
>  aMorph := self costume chooseClickTarget. "<- this part changes  
> the mouse pointer of the world from arrow to cross-hair"
>
> "The following part gives a message to self to set message target,  
> if a not nil morph is chosen then the selected morph is assigned to  
> aMorph variable, if is Nil, I'm not pretty sure what's happening"
>
>    self setMessageTarget: (aMorph
>        ifNil: [ActiveWorld presenter standardPlayer]
>        ifNotNil: [aMorph assuredPlayer])
>
> -----
>
> I'm seeing that the world is "holding its breath" until a morph is  
> chosen, and everything stops for a while until the target of the  
> message has been choose. I image that this is related with the code  
> "ifNil: [ActiveWorld presenter standardPlayer] ...". There is a way  
> to keep the objects in the world moving, even with the message  
> target still to be selected?

Actually, it's the "chooseClickTarget" which does all the work, and  
which causes the system to "hold its breath".

This breath-holding is not absolutely necessary, it's just that  
that's how the underlying support for morph-picking has always worked  
in Squeak -- i.e. totally modally.

To explore the possibility of relaxing this limitation, I've made a  
suggested fix and included it in the attached revised version #5 of  
the StarLemmings project; in this version, things will continue to  
breathe during target selection.  Please try it out and let me know  
what you think.


Cheers,

  -- Scott

PS:  Just as an aside, I think that perhaps better than trying to  
learn Smalltalk by puzzling over little oddball textual snippets such  
as the one I provided for this project would be to download some of  
the great and free Smalltalk books (including a nice one in Spanish  
by Diego) from Stephane Ducasse's wonderful web site, which you  
probably already know about:

http://www.iam.unibe.ch/~ducasse/FreeBooks.html



ATTACHED:  StarLemmings.5.pr, revised version of the StarLemmings  
project which allows breathing during morph-picking.


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