QTreeWidget speed, was Re: KListBox/KIconView/KListView

[Simon Hausmann]

On Thursday 05 January 2006 17:40, Simon Hausmann wrote:
> On Wednesday 04 January 2006 22:38, Matt Newell wrote:
> > On Wednesday 04 January 2006 15:13, Benjamin Meyer wrote:
> > > [snip]
> > >
> > > > and on that topic, hopefully QTreeWidget will be made to be non-slow
> > > > in 4.2 too. try adding 100,000 items to a QTreeWidget and watch how
> > > > adding slows to a crawl =/
> > >
> > > For those who haven't seen it, one problem I saw was that as you added
> > > one row at a time (vs one big block insertRows(0,10000) ) it was taking
> > > longer and longer, adding 100 rows to 100 was taking 200ms, 100 to
> > > 10,000 was taking 8000ms. etc"  Adding 10,000 rows could take a number
> > > of seconds. Not good
> > >
> > > But do not fear!  I have profiled and improved (dramatically in some
> > > places) a number of spots in itemviews, in particular when data changes
> > > and when new items are added to tree view and tree widget.
> > >
> > > Adding 100 rows now takes about 5ms be it to 100 or 100,000 :)  The
> > > fixes will be in 4.1.1.
> > >
> > > Course when you have 100,000 items you probably want to have your own
> > > model. Models are cool*.
> > >
> > > -Benjamin Meyer
> > >
> > > *delegates are there own class of cool because they facilitate
> > > eye-candy.
> >
> > This sounds good, but another speed problem on linux is text painting, it
> > can cause large treeview widget with many columns to take a lot of time
> > to paint. This patch speeds up text painting quite a bit for me, not sure
> > if it is correct.  It causes XRenderCompositeText32 to be called per line
> > instead of per glyph.  This should really be looked into, because it
> > really causes most of the drawing slowness for my apps.
>
> Unfortunately this patch breaks kerning.

Nevertheless I just realize that it's easy to extend your patch to support 
both, RenderCompositeText32 calls with combined elts for glyphs without 
kerning.

Please follow Benjamin's advice and submit your patch via the feedback form or 
directly by mail to qt-bugs.


Simon