Hello Klaus,
On 09/13/2018 10:58 AM, Klaus Espenlaub wrote:
Hello Steve,
this "do what I want" request is tons more effort than what you think.
This wasn't a request that it be implemented, only a general
question as to whether there was a current API for it. :)
1. What is "the host display"? By default the VM is shown in a window,
which can span multiple physical screens.
Ok.
Also, what should happen in
the headless VM case when the screen is accessed using an RDP client?
Ah yes, good point.
2. Getting the vsync state is extremely host OS dependent, so it'd need
a whole machinery for abstracting this enough. Likely this would need to
bypass Qt and then life gets very hard.
Agreed.
3. While page flipping is minimizing tearing, it also means that on
every flip the entire VM screen content will be updated (no easy way to
figure out what actually changed). This means the screen updating will
be less efficient than when doing the updates in place.
All of this is fixable. After all we're talking about software. It's a
cartload of work for very little gain, though.
Thanks for clarifying the difficulties. I don't have the bandwidth or
expertise in all the supported hosts to work on this myself, so chalk
it up as a possible TODO if tearing is indeed observed on page flips
in the future.
Steve
Just my 2c,
Klaus
On 03.09.2018 10:26, Michael Thayer wrote:
Hello Steve,
Nothing at the moment I'm afraid. It might be something we could
consider adding some time (though it would be far from trivial, since we
have four supported and additional unofficial host ports to make it work
on). It is also something we might accept a patch for. One of the
relevant code-owners is not available for the next week, so I can't say
for sure.
Regards
Michael
31.08.2018 22:54, Steve Longerbeam wrote:
Hello VBOX developers,
I recently contributed a patch to in-kernel vboxvideo DRM driver which
adds support for page flip. However the implementation does not
make any attempt to sync page flip with host vertical blanking
interval, so it's possible a DRM page flip will result in tearing
artifacts.
So is there a call that can be made into the hypervisor that would allow
receiving an event when host display has entered a vblank interval?
Something in the VBOX Main API perhaps?
Thanks in advance,
Steve--
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