Re: [Qemu-devel] VNC patch, the 3rd version

[Jim C. Brown]

On Sat, May 29, 2004 at 08:18:10PM +0200, Johannes Schindelin wrote:
> Hi,
> 
<s>
> There is a problem with the synaptic patch: If I read it correctly, the
> absolute flag cannot be set to 1. There is simply no line which can do
> that.
> 

Correct. To do that on a real touchpad you have to set bit 7 of the mode bit
to 1. My patch doesn't support setting the mode bit.

> Jim, if you read this, can you help a mediocre programmer and enlighten me
> how to use your work?
> 

For now what you need to do is:

The simple yet ugly hack would be to, on line 732 of pckbd.c, check if bit
7 of val is set. If so, set absolute mode on.

if (val & 0x80) s->touchpad.absolute = 1; /* TODO: real support for changing 
the mode byte */

I'm trying to figure out how to implement this elegantly and support all
possible modes. As you can tell by my silence, I haven't figured this out yet.

> Another idea which hit me: I am not convinced that without guest drivers,
> the synaptic patch helps VNC's mouse.

It doesn't. Without guest drivers, the real touchpad emulates a normal mouse.
Unless absolute mode is turned on, the patch doesn't add much.

With absolute mode, it still doesn't add much due to missing functionality
such as guestures. How would I emulate guestures with a 2-button mouse
is the question here. (Emulating a third button or scrolling with a real mouse
that has a real scrollwheel is not that hard, but with a mere 2 button mouse
the problem becomes much harder.)

> So why not use the
> graphical feedback when using the mouse to determine where the guest
> cursor is now (and how far it lags behind/runs in front)? I know, it is
> less than clean, but it would be fun! I think I will try it if nobody
> yells at me.

Good luck. This will not be easy at all (for example, what if the guest OS is
showing a screenshot, which happens to include the image of the mouse pointer
-- and remember that each GUI has a different looking mouse pointer, and most
have several, which can be swapped in at random from the viewpoint of qemu) but 
if you can pull it off it could be a useful feature.

> 
> Ciao,
> Dscho
> 
> 


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