[Kde-games-devel] Meetings and results

[Ian Wadham]

On Wed, 5 Sep 2007 10:45 pm, Mauricio Piacentini wrote:
> Mauricio Piacentini wrote:
> > I think we need a direct channel with the TT guys that could help us
> > understand what has changed, and what to do. Aaron, can you help with
> > this particular issue?
>
Definitely.  We're in deep trouble if a Qt graphics change with this kind
of effect on image quality happens again, maybe just before a major
release milestone.

> Just to make it clearer, I already looked at the public available
> information about 4.3.0->4.3.1 changes, and there is nothing noticed for
> QtSvg. There are some bug fixes in QGV, but we saw problems in programs
> that did not use it (KGoldRunner), so we can safely discard it as the
> main source of this particular problem. FYI the list of changes URL is at
>
> http://trolltech.com/developer/notes/changes/changes-4.3.1/
>
I think the change that affects us may be in QPainter.  On the page you
quote above, this QPainter fix looks a little as if it might be involved:
      "[167497] Fixed color bleeding artifacts at the edges when drawing
      images/pixmaps with SmoothPixmapTransform on X11."
Or some of the other QPainter fixes might be related.  Hard to tell.

FWIW, here's my theory of a couple of weeks ago, 25/08/07, on
thread "[Kde-games-devel] KGoldrunner themes".

"I wonder if it is related to the 0.5 pixel all-around that QGV adds/added(?)
to every pixmap size, to allow for anti-aliasing.  A side-effect was that
exactly adjacent tiles in KGr were seen to be overlapping, so QGV would
repaint nine tiles every time you picked up gold and changed one tile.  This
was not the main QGV overhead that affected KGr, however."

"Maybe Trolltech moved the half-pixel trick into the QPainter in Qt 4.3.1
to save some overhead in QGV (e.g. reduce pixmaps by 0.5 pixels all
around before antialiasing and painting), but I cannot see any mention
of it in the 4.3.1.change list.  If true, it might account for Luciano's and
Mauricio's observation of cracks between the bricks in Qt 4.3.1."

I do not think it would be a QSvgRender thing.  If it is, I would expect
the cracks to get bigger at bigger resizes and a fixed 0.5 pixels all
around to be insufficient to correct it.

Cheers, Ian W.