[Qt-interest] Strange QGraphicsItemAnimation behavior

[Thomas Fjellstrom]

On Tue January 5 2010, Jason H wrote:
> Well, you shouldn't move your item position. You need to set the scale,
>  but use a transform that is translated by (-dx/2,-dy/2) then scaled then
>  translated back.

I don't think I want to scale. Given how small each "tile" will be in some 
cases, I actually want them to get larger when moused over, so there's more 
actual room, not just scaled space.

> In the new QGVA stuff, it is called transformOrigin()
> 

Yeah, I switched to the new QPropertyAnimation stuff today. Works rather 
nice.

I found my bug too. Turns out stop() on either QGraphicsItemAnimation or 
QPropertyAnimation will do some really funky things. After checking properly 
for different conditions, and calling ->pause() instead, my game board 
renders pretty much perfectly :D

Qt 4.6 also lets me "flip" my fancy login and register dialogs rather than 
the lame slide I had before.

> 
> 
> ----- Original Message ----
> From: Thomas Fjellstrom <tfjellstrom at shaw.ca>
> To: Jason H <scorp1us at yahoo.com>
> Cc: Qt Devel <qt-interest at trolltech.com>
> Sent: Mon, January 4, 2010 10:57:44 AM
> Subject: Re: [Qt-interest] Strange QGraphicsItemAnimation behavior
> 
> On Mon January 4 2010, you wrote:
> > I think you should use the new animation API.
> 
> I am planning on upgrading to Qt 4.6, but not right away. Probably when
>  it makes it into Debian Sid's repo.
> 
> > Using all those timelines
> >  sets up multiple timers. You need to use a singleton timer technique
> > so there is only one timer driving all the events.
> 
> That would result in the same problem I'm seeing now. One timer seems to
> effect the rest for no good reason I can think of. I want items to keep
> animating till they stop, not jitter around when others are running.
> 
> > ----- Original Message ----
> > From: Thomas Fjellstrom <tfjellstrom at shaw.ca>
> > To: Qt Devel <qt-interest at trolltech.com>
> > Sent: Sun, January 3, 2010 11:58:27 PM
> > Subject: [Qt-interest] Strange QGraphicsItemAnimation behavior
> >
> > I'm having a small problem with multiple QGraphicsItemAnimation's and
> >  their assigned QTimeLine objects being affected by other running
> >  QTimeLines.
> >
> > Basically, I have a GameBoard (QGraphicsWidget sub) class that is
> > filled with many GameBoardSquare (QGraphicsWidget sub) classes (laid
> > out in a QGraphicsGridLayout), and each GameBoardSquare animates as the
> > mouse enters, and leaves the square. What I've found happens, is that
> > when multiple QGraphicsItemAnimations (with their respective QTimeLine)
> > are running, they are effected by other running animations for some
> > reason.
> >
> > I know the code I've attached isn't all that pretty, and the animation
> > handling isn't quite correct, but it aught to work. Mousing over an
> > item, without having been over another item for a long enough period as
> > to wait out any running animations, and the animation plays correctly.
> > Mouse over an item directly from another, or while another is
> > animating, and you'll see the item you have the mouse over jitter, or
> > change its position incorrectly while its animating, and most of the
> > time, the final position is wrong as well.
> >
> > I'm using Qt 4.5.3 on debian linux.
> 


-- 
Thomas Fjellstrom
tfjellstrom at shaw.ca