Form element rendering regression

[Germain Garand]

Le jeudi 3 juillet 2008, Harri Porten a écrit :
> Hi!
>
> Since several weeks/months KHTML exposes a somewhat ugly rendering
> problem. It manifests itself as a block of elements (always form elements
> I believe) being rendered at a wrong place of the screen unless one
> performs an action like scrolling.
>
> Steps to reproduce (credit go to Teve):
>
> 1.) Browse to http://marc.info/?l=kde-core-devel&r=2&b=200806&w=2
>
> 2.) Assure that the window is small enough to require scrolling
>
> 3.) Scroll down to the bottom of the page
>
> 4.) Press next
>
> More often than not one now sees the Search field and buttons being shown
> at the top of the page although they should be out of the visible area.

Just to note I could reproduce that bug indeed.
I don't see it being related to widgets though, and rather than a block 
rendered at the wrong place, I observe a block drawn at the correct place, 
but over previous content that is not erased.

Could be backingstore/scrolling related. Or a bug in background painting of 
replaced elements.

Greetings,
Germain