Re: redisplay system of emacs

[grischka <grishka@gmx.de>]

>> Redisplay_internal does lots and lots of computations to detect which part
>> of the buffer should be redisplayed at a given moment. All these
>> computations can be avoided using a system of subwindows (1 for every
>> char).
>
> Those computations are complicated because the buffer contents (or window
> width, or scroll amount, or...) might have changed, not just because the
> window might have been damaged in some complicated fashion.

It's not _that_complicated.  Basically it just draws the new screen to
memory, then compares it with the current screen and then updates the
differences.

And actually it works nicely and fast, just maybe slightly over-designed
in cases.  (For example changing "bazfoobar" to "baz,foobar" would output
",f" and "obar" and thus reuse the originally second "o" for the new first
one.  One might think that drawing one additional "o" could be faster than
two XDrawString, but so what).

Whether the code could be written to be easier to understand is a different
question but who has time for cleanups anyway.

--- grischka