[Squeakland] pen trails over sketch

Scott Wallace scott.wallace at squeakland.org
Tue Jan 10 21:44:23 PST 2006

At 8:24 AM -0500 1/10/06, Randy Heiland wrote:
>Apparently I only dreamed this was possible in etoys?  In working with my
>class at Girls Inc last night, a girl had painted an "ocean" as one object,
>then a fish as another, then attempted to have the fish's pen trails show up
>over the ocean.  It wasn't possible - the pen trails only showed up behind
>the ocean - in the "world".  The same is true in Tweak it seems.  Is this
>possible and I've simply forgotten how?

Hi, Randy,

The only objects that can bear pen-trails are "playfields", also
sometimes called "PasteUpMorphs".

So when an object draws pen-trails, the trails appear on the
containing playfield of the object; if its immediate container is
*not* a playfield, then the *container's* container is used, and so
forth up the line until a containing playfield is found.

Since the entire squeak "desktop" (a.k.a. the "World") itself is a
playfield, that's where most pen-trails end up getting deposited.

For the example you mention, make the "ocean" be a playfield.  Give
it a sea-like appearance by painting its "background picture," which
you can draw/change by clicking on the playfield's "repaint" halo handle.


    -- Scott

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