[Cuis-dev] listening for TextModelMorph changes

[Mark Volkmann]

Thanks for the further clarification. It seems this is what I really need
in order to evaluate a block of code each time a key is pressed in the
TextModelMorph:

input := TextModelMorph withText: 'edit me'.
input keystrokeAction: [ :evt | evt keyValue print ].
input openInWorld.

On Mon, Jan 13, 2025 at 10:02 PM Weslleymberg Lisboa <
weslleym.lisboa at gmail.com> wrote:

> Em 13/01/2025 22:29, Mark Volkmann escreveu:
> > Thanks so much for this tip! Clearly a key to getting this to work is
> > knowing the symbols that the watched object passes to the changed:
> > method. I see that the TextModel instance method actualContents: uses
> > the symbol #actualContents. So I tried the following to test whether I
> > could make a sound every time the text in a TextModelMorph is modified:
> >
> > Preferences at: #soundsEnabled put: true.
> > model := TextModel withText: 'Hello'.
> > model when: #actualContents send: #primitiveBeep to: Smalltalk.
> > input := TextModelMorph withModel: model.
> > input openInWorld.
>
> If you look the implementation of #changed: you will see that it
> triggers a #changed: event passing along whatever symbol it received as
> argument. This should print 'actualContents' in the Transcript:
>
> model := TextModel withText: 'Hello'.
> model when: #changed: send: #log: to: Transcript.
> model actualContents: 'Hello!'.
>
> It won't work with #primitiveBeep because the #changed: event always
> comes with an argument. But the following should produce a sound:
>
> model := TextModel withText: 'Hello'.
> model when: #changedContents send: #primitiveBeep to: Smalltalk.
> model triggerEvent: #changedContents.
>
>
> > I don't hear sounds when modifying the value. I thought perhaps the
> > problem is that the TextModel instance method actualContents: is not
> > called every time the value is modified. But even when I explicitly
> > invoke it with model actualContents: 'Test', I don't hear a sound. I do
> > hear a sound when I evaluate Smalltalk primitiveBeep.
>
> In fact, TextModelMorph never calls #actualContents:. This is
> interesting. I did some digging and following a key stroke the Text
> instance that TextModel holds will be modified and the morphs involved
> in the process will redraw. So the "Observer Pattern events" we are
> trying to catch here will only happen when the TextModel changes for
> some reason outside the event processing (mainly keyboard and mouse
> events) done by TextModelMorph.
>
> In summary, if a change in the model is caused by an interaction with
> TextModelMorph, the Morph knows about the change and will update itself.
> But it has no way to know if the model changes by other means. This is
> where the Observer Pattern comes into play.
>
> I just learned a lot trying to understand all this :)
>
> --
> Wéslleymberg Lisboa
> Graduado em Sistemas de Informação
> Docente no IFFluminense - Campus Itaboraí
>
>

-- 
R. Mark Volkmann
Object Computing, Inc.
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