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

["andrzej zaborowski" <balrog@zabor.org>]

On 20/03/07, Anthony Liguori <anthony@codemonkey.ws> wrote:
> Thiemo Seufer wrote:
> > andrzej zaborowski wrote:
> >
> >> This should allow the emulated video cards that support hardware
> >> accelerated cursors to relay the cursor drawing to host, possibly
> >> using real hardware cursor. This way the guest and host effectively
> >> share one cursor. Only SDL support is included. Not tested with mice
> >> that report absolute coordinates.
> >>
> >> The cursor does not appear in the framebuffer seen by the guest, it's
> >> only drawn on the host. One funny effect is that it's not clipped to
> >> the size of the framebuffer and can stick out of the SDL window.
> >>
> >> I think the sdl.c could use a small rewrite to have all cursor hiding
> >> and showing in one place instead of spread across the file.
> >>
> >> VNC support would need employing an extension for this, according to
> >> Anthony Liguori. VMware made a documented VNC extension that does it.
> >>
> >
> >
> >> From 3cf77a8b3c80b0306a0e73677ac6faeb1f83e0a2 Mon Sep 17 00:00:00 2001
> >> From: Andrzej Zaborowski <balrog@zabor.org>
> >> Date: Sun, 11 Mar 2007 15:31:12 +0100
> >> Subject: [PATCH] Host-accelerated mouse cursor support in SDL.
> >>
> >
> > This patch breaks scrolling in the cirrus vga framebuffer.
> >

I will try to see why it breaks scrolling after I fix the VMware SVGA.
It shouldn't affect anything other than the mouse cursor, and only
when enabled by the SVGA.

>
> I think we want to expose these functions via DisplayState.  It would be
> nice if the semantics of too were similar to the rest of the functions

Agreed. They should be accessed through ds->mouse_set.

> > (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.

> 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.

Regards,
Andrzej