QTreeWidget speed, was Re: KListBox/KIconView/KListView

[Benjamin Meyer]

Cool, you should send it to trolltech 
( http://www.trolltech.com/forms/feedbackform.html ) they will route it to 
the appropriate people (and make sure it doesn't get lost on a mailinglist).

-Benjamin Meyer


On Wednesday 04 January 2006 10:38 pm, 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.
>
> --- /mnt/storage/qt4snap/src/gui/painting/qpaintengine_x11.cpp  2005-12-20
> 16:39:59.000000000 -0800
> +++ /mnt/storage/qt41rc1/src/gui/painting/qpaintengine_x11.cpp  2005-12-12
> 12:24:13.000000000 -0800
> @@ -2103,26 +2101,42 @@
>          GlyphSet glyphSet = ft->glyphSet;
>          const QColor &pen = d->cpen.color();
>
>          ::Picture src = X11->getSolidFill(d->scrn, pen);
>
>         XRenderPictFormat *maskFormat =
> XRenderFindStandardFormat(X11->display, ft->xglyph_format);
>
> -        QVarLengthArray<XGlyphElt32, 256> glyphSpec(glyphs.size());
> -        for (int i = 0; i < glyphs.size(); ++i) {
> -            int xp = qRound(positions[i].x);
> -            int yp = qRound(positions[i].y);
> -            if (xp > SHRT_MIN && xp < SHRT_MAX) {
> -                glyphSpec[nGlyphs].glyphset = glyphSet;
> -                glyphSpec[nGlyphs].chars = &glyphs[i];
> -                glyphSpec[nGlyphs].nchars = 1;
> -                glyphSpec[nGlyphs].xOff = xp;
> -                glyphSpec[nGlyphs].yOff = yp;
> -                ++nGlyphs;
> -            }
> +               int neededElts = 1;
> +               int y = qRound(positions[0].y);
> +               for( int i = 1; i < glyphs.size(); i++ ) {
> +                       int yp = qRound(positions[i].y);
> +                       if( y != yp ) {
> +                               y = yp;
> +                               neededElts++;
> +                       }
> +               }
> +
> +        QVector<XGlyphElt32> glyphSpec(neededElts);
> +               int n = 0;
> +        for (int i = 0; (i < neededElts) && (n < glyphs.size()); ++i) {
> +                       int ys = qRound(positions[n].y);
> +            int xp = qRound(positions[n].x);
> +                       if (xp > SHRT_MIN && xp < SHRT_MAX) {
> +                               glyphSpec[i].glyphset = glyphSet;
> +                               glyphSpec[i].chars = &glyphs[n];
> +                               glyphSpec[i].nchars = 0;
> +                               glyphSpec[i].xOff = xp;
> +                               glyphSpec[i].yOff = ys;
> +                               while( ys == qRound(positions[n].y) ) {
> +                                       glyphSpec[i].nchars++;
> +                                       n++;
> +                                       if( n >= glyphs.size() )
> +                                               break;
> +                               }
> +                       }
>          }
>
>          int i = 0;
> -        while (i < nGlyphs) {
> +        while (i < neededElts) {
>              XRenderCompositeText32 (X11->display, PictOpOver, src,
> d->picture,
>                                     maskFormat, 0, 0, 0, 0,
>                                      glyphSpec.data() + i, 1);
>              ++i;
>          }

-- 
aka icefox
Public Key: http://www.icefox.net/public_key.asc
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