Ugly borders in Seamless mode with Linux Mint and Windows 10

[AdriFandango]

Hello,

I've been trying to make seamless mode work correctly with my system because i find it very useful, but i can't possibly make it look good, there are really ugly borders showing the background in every window from the guest SO.

I've tried disabling shadows, disabling and enabling 3d hardware acceleration, switching from compiz to metacity and viceversa and trying to change the compiz settings, but none of them worked.
Also my resolution is the same in the native and guests systems, so i don't think that is the problem either.

I don't know what to do anymore
¿Does anyone know why this problem could be happening?

I'm using Virtual Box 5.2.18 in Windows 10, running Linux Mint 18.3 with cinnamon desktop.

Thanks a lot in advance.

[socratis]

There are issues with the X11 interaction. A lot of issues. And with the multitude of combinations of DE/WM/OSes, it's really difficult to address. So much so, that the developers have pretty much declared the X11 related issues as user supported. Which means if a competent user knows how to fix it by changing the source code, fine. Otherwise they won't devote any more time, any time soon.

There is call for help from the developers for end-users to pitch in helping with this: 3D support for X11 guests. Also, see a relatively recent comment about this:

Just to summarise the situation: we do not currently have free developer time (as in developers with the required skills who are not already taken up with other work) to investigate this bug, much as we understand that it is annoying to the people affected. This situation might change, but that is not something we can promise. Of course, I quite understand that if this means that something else fits any individual's requirements better than VirtualBox then it is a sensible solution to use that instead.

However, the fact that VirtualBox is open source means that users who are interested have another option to get changes made, by doing the work themselves or crowd-sourcing the work. If you go this way of course, please communicate with us before starting and while doing the work, as we hate to see work go to waste due to misunderstandings like mismatches with our development style. Though this is more a fix than a feature, so likely to be easier to integrate.

See also the X11 guest 3D wiki page. Windows guest 3D is not user-maintained, but we are still rather limited in what we can do.

I would kindly request that as of now people do not add unneeded information to this ticket, such as that this is still not fixed or does not work for a given person. However, if you would like to subscribe to the ticket please add a "me too" comment, and we will delete the comment and add your nickname to the "CC" list.

[Shmu26]

There are issues with the X11 interaction. A lot of issues. And with the multitude of combinations of DE/WM/OSes, it's really difficult to address.

Is there any host OS and/or desktop environment that is less problematic in supporting seamless mode for a Windows guest? Or a certain version of VB that supports it better?
I know from experience that among the possible guests, W10 performs poorly in seamless mode.