Stefan Schimanski wrote:
Hi!
It seems that a big annoyance for many people is the bad scrolling in
1.5 and 1.6. The paragraph heights are estimated by some tricky logic
which more or less takes the average of the visible paragraphs. The bug
report: http://bugzilla.lyx.org/show_bug.cgi?id=2426
Is anybody working on this?
I've played with it a bit together with Tommaso (off-list).
I was playing around with the straight forward approach to cache the
paragraph heights in some map which maps Paragraph* to height. Then
instead of using the estimate to guess a size for invisible paragraphs I
just used a loop to add up the cached values (this could be improved of
course by some clever use of a balanced binary tree to get sums up to
every paragraph for free).
Of course the whole approach only works if the cache is filled (enough)
with real heights. This is not the case at the beginning. But as soon as
it is filled you get perfect scrolling behaviour.
I think most other applications do some layouting in the background to
get those height values. Has anybody tried to do the same with LyX?
One could fill up the height cache in idle times for example after the
document is loaded, maybe with some regulation to not stress the machine
too much.
This is exactly our plan ;-)
I don't think this is solvable easily in 1.5 but this is easily solvable
for 1.6.
You don't really need a map. A vector of height for the outermost
paragraphs should be enough. Initially the vector would be filled with
nominal values. Each time a paragraph metrics is calculated, the nominal
value will be replaced by the real height. We have to be careful to
maintain the vector in line with the main paragraph list.
If the user experience is not good enough, we can add one or two
paragraph metrics calculations at each cursor blink.
Abdel.
