Hi,
When you open a morph for dropping it will accept all dropped morphs:
joe dropEnabled: true.

To filter what is accepted you must override acceptDroppingMorph: aMorph
event: evt
Look at implementors for that method.

Best,
Karl



On Mon, Jun 15, 2020 at 2:44 PM Trygve Reenskaug <trygver at ifi.uio.no> wrote:

> Hi Squeakers,
> My SRE context browser is a tool for drawing a snapshot of a selected
> structure of interlinked objects where each object is shown as a
> rectangular symbol. This diagram shows an object with its class and
> superclass objects:
>
>
> SRE has worked for years, last in 'Squeak3.10.2'. In 'Squeak5.3', the same
> program went into an infinite loop. It transpired that *myClass>>processEvent:
> anEvent using: defaultDispatcher* had become a new thing called an event
> filter and needed to return an Event or a Symbol. That problem fixed; the
> program still misbehaves. The problem seems to be with event handling. I
> have never been into that corner of Smalltalk but have read some Squeak
> documentation. I have not found any concrete code.  I realize that I will
> never understand Squeak's event handling by reading code, code comments,
> and even the documentation I have found. There has apparently been a
> significant increase in complexity lately. An example: In 3,10,2, class *MorphicEventDispatcher
> *has 4 methods. In 5,3, it has 16.
>
> Here's the beginning of my challenges with 5.3: I find two anomalies in a
> diagram with just one symbol:
>
>    1.     When I move some other window to a position within the diagram,
>    the diagram grabs it and makes it a submorph of itself.  In 3.10.2, the
>    diagram ignores it.
>    2.     The cursor becomes a text cursor when I move the mouse across a
>    symbol.
>
> I have no explanation for either anomaly. My SRE code is a kludge and is
> almost unreadable. It is hard to formulate a question without the whole
> code as a background, and I have tried to reproduce them in a simple
> example. I managed to reproduce the first, but not the second anomaly. In a
> workspace, copy, select,  and do it. The XXX-symbol becomes attached to the
> cursor, and I place it in the blue background.
>
> joe := PasteUpMorph new color: Color lightBlue.
> joe bounds: (500 at 400 corner: 800 at 600).
> joe dropEnabled: true.
> joe openInWorld.
> circle := CircleMorph new.
> joe addMorphCentered: circle.
> tex := TextMorphXX new
>         contents: 'XXX';
>         borderWidth: 1;
>         color: Color red;
>         extent: 100 at 100.
> tex openInHand.
>
> There is only one  method in class TextMorphXX (sco TextMorph):
>
> processEvent: anEvent using: defaultDispatcher
>     ^#rejected
>
>
>
> I move some background window,  actually a collapsed Monticello thing, to
> Joe's position, Joe grabs it and makes it into a submorph. Any hints about
> how to proceed will be greatly appreciated.
> --Trygve
>
>
>
>
>
>
> --
>
> *The essence of object orientation is that objects collaborate  to achieve
> a goal. *
> Trygve Reenskaug      mailto: trygver at ifi.uio.no <%20trygver at ifi.uio.no>
> Morgedalsvn. 5A       http://folk.uio.no/trygver/
> N-0378 Oslo             http://fullOO.info
> Norway                     Tel: (+47) 468 58 625
>
>
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