Re: drawSelfOn:

[Marcus G. Daniels]

>>>>> "FW" == Fred Wan <address@hidden> writes:

FW> I have trouble understanding the following fragment in
FW> SimpleObserverBug and translating it to Java. Can someone help me
FW> out here? Especially the M(drawSelfOn) is puzzling. In jheatbugs a
FW> message is sent to a heatbug object that then draws itself, but
FW> what happens here is unclear.

It's the same idea.  The drawSelfOn: message gets sent to the Bug instances
in the world.  drawSelfOn: gets passed the raster that you specify
via setDisplayWidget:.  Without the argument, the Bug would not have any
info about where to draw itself.  (That's at the end of Bug.m.)

The setObjectCollection: is optional.  It makes it faster to send the
drawSelfOn: messages (otherwise it is necessary to look at all the points
on the grid).  The grid itself is specified by setDiscrete2dDisplay:, and
it is needed in order to track where Bugs are.


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