[pdftex] Caching intermediate compilation results for near-real-time PDF re-renders during editing

[Karl Berry]

Hi Jamie - thanks for the interesting message. Thanh could say more, but
FWIW, here are my reactions (in short, "sounds impossible").

    My understanding of pdftex is that it operates on a per-page basis.

Plus about a million global variables representing the state of
the compiler. (All the TeX engines are similar in this regard, having
inherited their basic architecture from Knuth's tex.web.)

    Suppose a small change is then made to the latex source, such that the
    compiler determines this change would first affect page k. 

I can't imagine how that could be determined without retypesetting the
entire document. There is no way to predict what any given change will
affect.

    possible in principle because this is the basis of operation of BaKoMa
    TeX, which I have used for years. 

That is amazing. I wonder if Malyshev's heirs can somehow be contacted
to get the source freed. We have had no luck even finding notices
beyond the bare fact of his death :(.

    I believe very strongly in the benefits of ultra-fast recompilation

I agree, but can't conceive of how Basil implemented what you describe.
A failure of imagination on my part, no doubt. --best, karl.