Morphic slowness, was: Re: The Puzzle Page

Bob Arning arning at charm.net
Tue Dec 19 15:11:03 UTC 2000


On Tue, 19 Dec 2000 11:10:59 +0100 (CET) Bert Freudenberg <bert at isg.cs.uni-magdeburg.de> wrote:
>> It seems the Morphic strategy is this: bottom-up [...]
>> A more optimal technique is: top-down [...]
>> Any thoughts from the graphics mavens?
>
>Morphic actually uses a top-down redraw strategy. It's soemwhat hidden,
>though. Check out WorldState>>drawWorld:submorphs:invalidAreasOn: (it used
>to be PasteUpMorph>>drawInvalidAreasOn: but Bob shuffles methods around
>faster than you can look ;^)

Bert & Henrik,

I would say that it is a combination. The strategy starts top-down to determine which morph(s) will be necessary to correctly draw a particular rectangle on the screen. Once those morphs are determined, that rectangle is drawn using those morphs from the bottom up, to insure that translucent areas have the correct background. As Bert pointed out, morphs which do not accurately answer #areasRemainingToFill: can lead to drawing errors or unnecessary extra drawing.

Cheers,
Bob





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