Asger Ottar Alstrup wrote:
Jean-Marc Lasgouttes wrote:
I see. Isn't there some performance price?
Yes, but it is not noticeable in our testing. After all, we only paint
two extra paragraphs.
I guess this is not something I can consider for 1.4.
Sure it is. Without, the coord cache is full of crap, and that causes
assertions and crashes.
[Smarter redraw]
Are there plans to implement that for 1.5?
We have looked a lot on performance work for 1.5, we have done a lot of
profiling, but there are no easy ways out.
Did you investigate if the emission Buffer::changed() instead of direct
WorkArea::redraw call was the real culprit of Lars reported typing slowness?
The best bet is André's patch
which will avoid an extra copy of the complete workarea pixmap. That
should help a lot, especially on windows.
Interesting.
Other than that, we strongly suggest to wait until 1.6 for this work,
because it will require time to stabilize. The reasoning is this: 1.4 is
dead slow, 1.5 can be as well.
Ideas for doing less drawing include:
- Reintroduce the "draw only this paragraph" optimisation from the old
days. This is a little complicated, because that means we have to only
clear out part of the coord cache, and then rebuild just that part.
- Add a caching layer in the painter. Instead of drawing, collect all
drawing requests in a data-structure. The first time, just draw on the
screen from this data structure. Then remember the data-structure which
illustrates what is on the screen. When the next redraw comes, collect
all the drawing requests in a new instance of the data structure. Then
start comparing from the start and end of the old and the new
datastructures to find the middle part which is different. This will
correspond to the part of the screen which will need to be updated. Then
do just those paints. Extend the middle part until you get background
fill requests, because then we now the drawing requests are selfcontained.
This was exactly what I was investigation some months ago. But then why
not going to QPicture directly? This will need some changes to the core
but I really think that's the way to go.
Abdel.
