[Vm-dev] primitiveDisplayString fails on empty Strings

[Nicolas Cellier]

+1

2018-05-23 21:11 GMT+02:00 Fabio Niephaus <lists at fniephaus.com>:

>
> Hi all,
>
> I noticed that BitBlt's primitiveDisplayString fails relatively often and
> then found out that it's sometimes called to draw empty strings.
>
> `(ByteString allInstances select: [:ea | ea isEmpty]) size` revealed that
> there are 2245 empty strings in my image and I assume some of them must be
> either in the FrameRateMorph morph or in the Clock morph.
>
> Anyway...looking at BitBlt>>#primDisplayString:from:to:map:xTable:kern:,
> the fallback code basically does nothing if stopIndex is zero (`startIndex
> to: stopIndex do: ...`) which makes sense.
>
> What I think doesn't make sense is that the primitive fails in the first
> place. Instead of failing if stopIndex is not greater 0, I would suggest to
> use: `stopIndex < 1 ifTrue: [^ interpreterProxy pop: 6].` which cleans up
> the stack, leaves the receiver, and returns early.
>
> Let me know what you think!
>
>
> Fabio
>
>
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