dual document view for speedy use of read-only

12.5: adde/gui/dual document view for speedy use of read-only:

. in order to be quick, the typical help system is read-only;
but friendly would be quick and annotatable .
. an editor can be made very lightweight
if it does only small chunks of simple text;
. this is possible by a windowing system that is
combining 2 documents:
the readonly panes load quickly despite being large;
the mutable panes load quickly because they are small .
. when you ok the pane, it saves that pane as a temp' file .
. deleting part of a readonly pane simply redraws the pane
without the part you deleted .
. after your annotation session,
it will merge results in the background .

. the annotation window is attached to the side
at a point that starts at finding current wrapped line
where the anchor phrase is found .
. finally, in the background,
the edits are merged with the doc .

. another view of a faster edit system
is that old text is never modified,
it is simply interleaved with panes of new text,
deletions have their before&after's
presented in the same read-only pane,
but the drawing is simply skipping the deleted range;
this may seem like a complication,
but no more so than having to
draw segments in separate panes .
. if the text is not word wrapped, (has frequent newlines)
then it should do a heuristic about whether
the after-piece should be on a new line
or the same line with the before-piece .
. for transitioning from rom text to mutable text,
there should be separate panes
to speed up the layout engine .
. within a read-only doc, after making selection,
you can do 3 things:
add your comment { above, below} it,
or replace it .