[squeak-dev] Re: Building an dial with an arrow indicator

Rodney Polkinghorne rodneyp at physics.uq.edu.au
Wed Jun 8 04:17:31 UTC 2011


Jerome wrote:
> ... code ...
> Basically you update the indicator by calculating a vector and adding it to where you want the tail.

My first draft was similar to that.  Then I thought, hang on, I'm
using Smalltalk, not BASIC.  I shouldn't update the indicator.
Rather, I should ask it to indicate something, and it should know how
to update itself.  Things went downhill from there.

Suppose this is the answer - the dial should understand a #indicate:
message, and adjust its arrow.  Now suppose I want to embed a dial in
an instrument panel.  This looks like the same problem as embeding an
indicator in a dial, so let's solve it the same way, with
Panel>>indicateAirspeed:.  You can see where this is heading.  Is
there a solution other than
Airline>>indicateAirspeedToNavigator:ofFlight:using747withSerialNumber:?



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