[squeak-dev] SystemProgressMorph/ProgressInitiationException

Ralph Boland rpboland at gmail.com
Sat Sep 4 03:52:51 UTC 2010


A SystemProgressMorph is used to display progress while some computation
is being done.  Furthermore the progress bars can be stacked to show progress
of component computations within a computation.
This I understand and understand most of the code.
But not All.
What I have trouble with is understanding why a ProgressInitiationException
is needed.  In particular, String>>displayProgressAt:from:to:during:
does:
ProgressInitiationException
		display: self
		at: aPoint
		from: minVal
		to: maxVal
		during: workBlock.


This method sets a few variables and then does:

	^self signal

This signal is caught where upon A SystemProgress is started or extended with
an additional progress bar.

But I don't understand why sending a signal to a ProgressInitiationException
is needed to get the ball rolling,

Can someone please explain why things are done the way they are?


Regards,

Ralph Boland



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