Re: [Qemu-devel] [PATCH] Guest mouse cursor drawing in SDL

[Anthony Liguori]

andrzej zaborowski wrote:
> > > (the pixel format of the cursor was the same as the pixel format of
> > DisplayState).
>
> I'm not sure if we want to always use the same pixel format - for
> example with VMware SVGA and SDL in 16 bit mode, the cursor pixel
> format reported by guest Xorg was 8 bpp. This would mean two
> conversions instead of one: first VMware SVGA would have to convert 8
> -> 16 bpp then SDL 16 -> 1 bpp.

VNC expects the cursor data to be in the current pixel format.  The nice 
thing about this approach is you don't need to pass a bunch of pixel 
info (for instance, you don't need to pass the depth, endianness, etc.).

The Cirrus hardware cursor also has to be copied anyway and doing the 
conversion is really straight forward.

> > One question in my mind is what the alpha mask should look like.  All
> > that VNC (and SDL) can use is a 1-bit alpha depth.  That's all Cirrus
> > supports too.  VMware SVGA supports an 8-bit alpha channel though so it
> > may make sense to design the interface now to support that.
>
> VMware SVGA without CAP_ALPHA_CURSOR also does only 1-bit alpha. Maybe
> we should keep two masks - if the frontend (e.g SDL) supports only
> 1-bit alpha it would use only this basic mask - if the emulated VGA
> supports only 1-bit alpha it would leave the other mask opaque.

I thought about that.  Right now with my patch, the cursor mask is 
always 1-bit deep.  I was thinking that perhaps the right thing to do is 
to make it always 8-bits deep and then convert in VNC.

Do you think using the SDL cursor is all that useful?  As soon as gtk 
widgets get involved, the cursor becomes ARGB so in practice, I'm not 
sure that it's all that helpful.

BTW, I've got the ALPHA_CURSOR working with VNC.. it's very sweet :-)

Regards,

Anthony Liguori

> Regards,
> Andrzej
>
>
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