Re: [Qemu-devel] "invisible wall" patch

[Dan Sandberg <dan.sandberg@medsci.uu.se>]

Julian Seward wrote:

>Could somebody please commit, or at least consider committing, 
>Anthony Liguori's "invisible wall" patch, shown at 
>http://lists.gnu.org/archive/html/qemu-devel/2006-05/msg00112.html ?
>
>Without it, QEMU is essentially unusable on my SuSE 10 host; with it,
>the mouse stuff works perfectly.  A couple of other people on that
>thread had similar experiences with it.
>
>J
>
>
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The patch works perfectly here (qemu 0.8.1 on Windows XP host). Without 
it I always get the invisible wall if I leave mousegrab and enter it 
again close to a window border.
It seems to me that SDL only reports pointer-deltas based on the 
movement of its own pointer (which is set invisible) and when this 
invisible pointer hits the window border you therefor only get delta=0 
even if the guest OS pointer is still somewhere in midscreen. (Setting 
the SDL pointer always visible gives a good illustration of what is 
going on.)
The guest-OS rather expects raw mouse movement deltas, than the filtered 
SDL-pointer deltas.

Somehow the patch seems to solve this, but I can't say that I understand 
how (not having looked into the SDL source code).

Regards
Dan Sandberg