Btw-- even for the size 1000 array above, part of the cpu usage and
sluggishness is caused by whatever computations pd is doing before sending the message
to the gui to create the next rectangle (see my message earlier in this
thread). So my example isn't exactly comparing tcl/tk speed to pd computation speed--
it's more like comparing a slightly bad apple to a much worse apple. In both cases I
think the significant "sluggishness" digits are due to whatever pd is doing
between message sends.
while no one has time to work on the real problem behind (described by
Jonathan), I would suggest a hack solution: instead of a copy of an image
(as suggested by someone), just turn the display off while the selection
is moving? doesnt' solve the real issue, but avoids some
dropouts/slugishness.