MacOSX Performance

Tim Rowledge tim at
Sat Jan 22 00:57:02 UTC 2005

Karsten Wolf <karstenwo at> wrote:

> In my image I don't find references to deferDisplayBits. Where should 
> they be? Perhaps you meant deferDisplayUpdates.
Yes, typo, sorry.

> Neither
> BitBltSimulation>primitiveDrawLoop nor 
> BitBlt|BitBltSimulation|InterpreterSimulator>drawLoopX:Y: contain a 
> reference to defer*. Rechecked this with a freshly unzipped 
> Squeak3.7-5989-full. What imageversion are you using?
Any vaguely recent version of VMMaker; deferDisplayUpdates is used in
Interpreter>showDisplayBits:Left:Top:Right:Bottom: which is called by

> I could have been more specific talking about 
> BitBlt>>drawFrom:to:withFirstPoint: which is not affected by any usage 
> of deferDisplayUpdates & is used when playing with Pen & Co.
That calls a copyBits for the first point, which calls
showDisplayBits, and then uses the primitiveDrawLoop which calls
showDisplayBits for every time the affected area (measured rather
tritely) exceeds 4000, not every time the copyBits is done.

Note that _only_ if the target Form is theDisplay does any call to the
platform specific code occur. Very often displaying os done to a buffer
Form and the updates are done later. Actual calls to update the screen
seem to be relatively rare when I have assorted tracing turned on for
my work on the VMs.

> That surely is more specific;-) I should have said that the windows vm 
> has some extra functionality accessible via some F-key... (haven't 
> looked at it for months)
I'm not at all sure that particualr facility is still used. But then, I
don't do windows anyway.

Tim Rowledge, tim at,
Strange OpCodes: CMN: Convert to Mayan Numerals

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