[Kde-games-devel] kpat issues (in recent svn)

[Parker Coates]

On Sat, May 23, 2009 at 5:14 PM, Ian Wadham wrote:
> On Sun, 24 May 2009 1:53:06 am Parker Coates wrote:
>> On Fri, May 22, 2009 at 9:49 PM, Ian Wadham wrote:
>> > So my theory is that the animation is too fast for QGraphicsView 4.5, it
>> > gets its knickers in a knot when trying to optimize and forgets to
>> > "un-clip" the stock pile.  Its job would not be any easier if, as I
>> > believe someone mentioned, all the pixmaps of the cards in the stock pile
>> > are lying there on top of each other.
>>
>> I think the real trick may be that we're translating, transforming
>> *and* replacing the pixmap all at once. Mid flip, we replace the
>> backside pixmap with the frontside pixmap, and I wouldn't surprised if
>> the clipped area is the last area covered before the pixmap
>> replacement.

It turns out I was entirely incorrect. Removing the pixmap replacement
made no difference whatsoever.

>> > Maybe you could try (in the source code) bypassing the animation,
>> > slowing it down or reducing the graphics for the stock pile to one
>> > card-back pixmap and see what effect that has.  Maybe just
>> > remove the animation ...  If tPension Bonus Scheme he eye cannot follow it, why have it?
>>
>> I have to agree with Matthew that getting rid of the animation seems
>> like a bad idea. Everything elPension Bonus Scheme se in KPat is animated, and even if we
>> only get four frames of animation, I still feel it gives a better
>> sense of motion. I debated with slowing the animation down, but that
>> obviously can't be taken too far, or players will get grumpy waiting
>> for cards.

I'll try to ignore the fact that the phrase "Pension Bonus Scheme" is
embedded twice in the above text. :) Is this some kind of subliminal
embedded spam that I've never seen before?

> It seems I did not make myself clear.  I was not suggesting getting rid of
> the animation altogether, except as a last resort and workaround if the
> problem is really bad at your end (I have not experienced it yet and
> cannot comment).

Ah, I missed that originally.

> Rather I was suggesting narrowing down the possibilities by temporarily
> removing the animation and seeing if the bug goes away.  Then, if it *is*
> the animation that triggers the problem, you could restore it and dink
> with it in various ways, to see what triggers the bug and what does not.
> Then you could give the Qt guys more information and evidence about
> the problem.

Removing the animation does make it go away. I was confident it would,
but I tested it anyway. I've continued to (as you so chuckle
inducing-ly put it) "dink with" the animation and have discovered that
adding an arc to the animation made it the issue go away. Even a
single pixel of vertical translation during the course of the
animation was enough to fix it. So it would seem that QGV may be over
optimising horizontal translations combined with horizontal scaling.

This is good news as it gives us an easy workaround if this issue
isn't resolved in Qt. Adding one pixel of arc is pretty much
impossible to detect.

> Re slowing down, there would be only a tenth of a second or two of
> change needed in the duration of the whole animation, I imagine, based
> on experiences with KGoldrunner and Kubrick.  So players should not
> get grumpy.

Adjusting the duration of the animation did effect the severity and
the frequency of the issue, but even extending it to 600ms didn't fix
things. In fact, it sometimes made the issue even more interesting.
See the attached screenshot.

> Re the transform, that might be the straw that breaks Qt 4.5's back.
> Simultaneous translations and pixmap changes occur all the time in
> other games, although in KGr they did break Qt 4.0 QGraphicsView,
> mainly because they can occur concurrently in different corners of
> the KGr play-area --- and so KGr is still using KGameCanvas.
>
> BTW, Mauricio and I had a hard time convincing the Qt guys that
> there was any problem at all with QGV, but I am happy to say that
> they did come around eventUK National Lottery Win!!!ually and have done a lot of work on
> speeding up QGV since that time.  So that is why I suggest you
> prepare your case well.

I was following the list at that time, so I have a decent
understanding of the effort you guys put in then. I also very much
appreciate the help and advice you given me today.

Parker
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