Re: OPENSTEP 4.2 vmware SVGA

[Frederic Stark]

Hi,

I looked more closely to what happens, and things are not as simple as I 
described.

The clock and the caret works perfectly (ie: they update in real time, 
without any phantom). But fast-moving the mouse or moving large chunk of 
graphics (ie: opening/moving/closing a window or scrolling) let large 
'bands' of the diplay untouched.

What I suspect is that vmware knows when the application touches the 
framebuffer and blit it to the real screen a few milliseconds later. But 
it looks like there is a race condition, and what is displayed during 
the blit is not displayed onscreen. So parts of large transfers are 
lost. I'll ask on the vmware newsgroups.

The MD5 trick (well, with a easier to compute CRC) could work. I could 
take a look at what VNC does...

Cheers,

--fred

Pascal Bourguignon wrote:
> Frederic Stark <fred@almonde.com> wrote:
>
> > Hi,
> >
> > Boring weekend. I took my OS42 CDs, vmware, the diff to the vmware 
> > module of XFree86, the drivers example from OS42, a dozen of cup of 
> > coffee and started to hack an OPENSTEP42 vmware SVGA driver.
> >
> > I am to the point where I get it running in 1024x768/24bits (yep, the 
> > values are hard-coded for now). Code is _very_ ugly, as this is my first 
> > OS42 driver (OS42 have no documentation on the DriverKit, and I can't 
> > get my hands back on my 3.3 CDs). I can probably get something more 
> > usable next week-end. I can release what I have for the impatient, of 
> > course.
> >
> > The problem is that the DPS server never tell my driver when screen have 
> > been written to, so vmware don't know when to update the real screen 
> > (ie: there are 'phantoms' left in a lot of places). I don't think the 
> > NeXT window server was ready to work with a 'buffered' device.
> >
> > Any idea about how I can solve that ? I can think about several solutions:
> >
> > 1/ Don't care (by moving the vmware window, the 'phantoms' disapear 
> > because vmware flushes the screen)
> >
> > 2/ Implement a /dev device and a user-land utility to tell the driver to 
> > flush the screen (every one second, for instance).
> >
> > 3/ Get a PostSript master to try to hack WindowPackage.ps to know if the 
> > server did something. Alternatively, I could try to patch the 
> > WindowServer binary.
> >
> > 4/ Play with mach memory to know if window server wrote to the 
> > framebuffer. Issue a flush to vmware 1/10th of a second later. It must 
> > be possible, but I have the slighest clue about how to do it.
> >
> > Any other trick ?
>
> The best  solution would be something like  3/, to have a  hook in the
> low-level    DPS     raster    routines.    That     would    be    in
> /usr/lib/NextStep/WindowServer, but it's  death-row software, not free
> software.
>
> But it would  be enough to have your driver  flush automatically 10 or
> 20 times  a second. Since flushing  to the screen could  be costly, it
> may be interesting to divide the  frame buffer of your driver in tiles
> and compute  a md5sum over  each tile, and  flush only the  tiles that
> have changed.
>
> Since there are the blinking carets, the clock, the cursor, the screen
> will need updating continuously, in small parts of it at least.
>
> The check sum computing frequency could be varied depending on whether
> the tile or its neighbor changed recently or not.