VMware & Wayland [WAS Re: Blender3D & cursor clamping]

[Thomas Hellstrom]

On 12/13/2010 09:41 PM, Kristian Høgsberg wrote:
> 2010/12/9 Thomas Hellstrom<thellstrom at vmware.com>:
>    
>> Kristian, Others,
>>
>> On 12/09/2010 08:36 PM, Kristian Høgsberg wrote:
>>      
>>>        
>>>> I'm interested in how Wayland deals with input&    about mouse coordinates.
>>>>
>>>> Currently Blender can fake off screen mouse coordinates on X11 by
>>>> hiding the cursor warping the position.
>>>> However it would be a lot nicer if the Wayland functions were able to
>>>> do this. (I heard this is possible on the OSX).
>>>>
>>>> Are there any docs on how to grab the mouse cursor, warp the cursor
>>>> and is there anything like raw events which can be used for low level
>>>> interface functions?
>>>>
>>>>          
>>> There are no docs, but we've discussed similar requirements before:
>>>
>>>
>>> http://lists.freedesktop.org/archives/wayland-devel/2010-November/000117.html
>>>
>>> The idea is what I call "application pointer" in that email.  The idea
>>> is that the compositor hides the cursor and just sends relative motion
>>> events.  The application is then responsible for updating cursor
>>> position, including pointer acceleration etc, or just not draw a
>>> cursor but spin a cube, rotate the viewport or control a game.  Now
>>> one thing I'd like to do different from X is that this mode isn't
>>> going to be an open ended grab.  The compositor is going to be in
>>> control and will be able to override it and switch to different
>>> applications.  I'm thinking that this input mode is only available
>>> when the application is fullscreen or optionally while a mouse button
>>> is pressed.  Maybe also while the application has keyboard focus.
>>>
>>> Kristian
>>>
>>>        
>> At VMware, we've started investigating what it would take to support
>> Wayland, both on the host side (workstation / player) and on the guest side.
>>
>> For the guest side, it doesn't seem to be too much work except we'd at some
>> point need full GL, and we perhaps need to find a way to optimize
>> pageflipping when we can't do it on real hardware.
>>
>> The tricky thing is the host side. I have a fairly elaborate list of
>> features, in particular including cursor warping and open-ended grabs that
>> we, according to the input people, can't work around and that are used on
>> all hosted systems, like Window, Mac and X11.
>>
>> So my question is basically, is there a chance for some flexibility here for
>> very demanding applications?
>>      
> Hi Thomas,
>
> We've talked about cursor grabs and warping before on the list as
> something games also want to do.  It turns out that typically what
> they really want is to draw their own cursor or no cursor at all, keep
> the cursor inside the window and receive relative events.  As far as I
> know, when the vmware host is running under linux, it runs in much the
> same mode.  Grabbing the cursor and continuously warping it into the
> window center is just how that is implemented.
>
> I'd like to support most of what application do under X, but maybe not
> exactly the way it works under X.  For the grab and warp case, I want
> to restrict this behaviour to when the application is active (has
> keyboard focus).  The compositor can always switch to a different
> application or the user can alt-tab (or whichever key the compositor
> uses) away from the application.  The way it will work is that the
> compositor stops moving the mouse cursor automatically, sends relative
> mouse events to the application, and the application can then maintain
> the cursor speed and position and place the cursor relative to its
> surface, or just hide it.
>
> This should work well for games, for nested Wayland or X servers or
> similar fullscreen experiences like the vmware host, qemu, vnc etc.
> Will that work for the case where you're currently using grabs and
> cursor warping?
>
> Kristian
>    

Hi, Kristian!

Thanks for the answer. I'm not the input expert so I'll discuss with 
them and see what might be missing.

Thanks,
Thomas