How does Acrobat Reader decide when negative kerning in TJ op. is wide enough to be taken as a space?

In some pdf documents, when TJ is used with kerning, Acrobat Reader considers some values as a space character. For example in this example

/F0 36. Tf
[(Hel)-10(lo)-200(Wor)-100(ld)] TJ

The -200 will be counted as space, while -10 and -100 won't be. This can be checked by searching for the following texts:
"Hello" -> finds Hello
"Hel lo" -> not found
"loWo" -> not found
"lo Wo" -> finds Hello World
"lo Wo" -> finds Hello World

My question is what is the input (matrices?, font spacing?, ...) and what is the algorithm for deciding whether to consider a negative kerning should be taken as a space.

Zoltan Kis

1 Answer

I think your best chance of getting a definitive answer to this is through Adobe's developer support program:

George Johnson   

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