Want Windows guest to cover 2 screens as 1

[UncleBoarder]

Is it possible to have my Ubuntu (16.04) host have 2 monitors but my Windows guest see it as just one superwide monitor?

I have two 1920x1200 monitors but I don't want Windows10 to know about them, I want Windows to see it as a single 3840x1200 monitor.

This same hardware worked this way with an older version of Ubuntu and VirtualBox. So I don't know if this just might be a problem with the newer software?

I have seen on this forum that the recommended way to accomplish full screen across two monitors is to configure my VBguest for TWO monitors and then extend my desktop to the second monitor in the guest os. This does work but it defeats my goal of Windows seeing it as a single monitor. This is not what I'm looking for.

I'm trying to get Windows to display a "full screen" of 3840x1200 on two physical screens of 1920x1200... But host-F takes me to full screen on just one monitor (1920x1200).

VB 5.0.18
VB Guest Additions is installed
I've also added a Hint address for the guest of 3840x1200

Some of you will ask why I want this... First it will extend my task bar across both monitors, extending the desktop doesn't do this. Second, presenting two screens to the guest will cause Linux to also see the guest as two separate screens when I'm using a task switcher or something similar, which is what I'm trying to avoid. When I have things stretched across two screens on my guest OS, I want them to appear that way to Linux as well, I do not want to use the "extend" box to display my guest os desktop across multiple monitors. I want my guest OS to think it's one big monitor.

Help please.

[mpack]

A VirtualBox VM will have two display windows if you configure two displays in the VM settings - the number of host displays isn't directly relevant. If you only want one then only configure one.

I believe you can have a single window spanning both displays if your host OS allows that. I can see it causing problems if two graphics cards are involved, with unequal capabilities.

[UncleBoarder]

I understand that and agree that it should work... so why does host-f give me 1920x1200 instead of 3840x1200.

As I said I do not want my VMguest to be aware of 2 screens so I believe I must set the guest to 1 monitor.

How do I make host-f go to 3840x1200?

(it's a single video card with two ports, which CAN handle the resolution)

I can manually stretch the display across both monitors but that only gets me close. I want edge to edge 3840x1200 like on my previous install.

If it's possible I need help to accomplish it.

[MPerz]

The problem you're experiencing is a limitation of the host, and not of Virtualbox. Your host sees the display topology as two separate devices and treats full screened application windows accordingly (Virtualbox console windows being no exception). To achieve what you described you would first need to determine if any desktop spanning capability is built into your host's display adapter - Nvidia's Mosaic utility or AMD's Eyefinity - and enable it. This would set the host to see your two separate monitors as a single display and would span application windows across both when maximized. Please note that this advice may apply to Windows hosts only; I don't know if the same or similar utilities are available for *nix.

[UncleBoarder]

My Linux install does see that I have two 1920x1200 screens so you may be right... but previous versions of Virtualbox allowed me to span these same two screens. I didn't have to convince Linux that I had a single 3840x1200 screen. I simply had to stretch my VirtualBox window and then go full screen.

Your answer makes sense except for one thing... I've seen many posts, I think even from moderators, that the VMguest doesn't care how many host displays exist, it's all about how many VMguest displays I configure. So, if that's true, in theory I should be able to configure my VMguest as 1 display, set the hint size as 3840x1200 and have it recognize 3840x1200 as full screen. But I've done that, and it doesn't work. It bounces back to 1920x1200.

So I'm thinking you are correct and all those posts who think that the number of host displays doesn't matter... well, they must be wrong.

But this leads me to think it IS a VirtualBox problem. Because host-f is a VirtualBox command, not a host command. So how VirtualBox processes host-f is the issue isn't it?

I think host-f should allow the hint size to override the single display size as "full screen". That would allow easy normal configuation as it works now, but it would give user flexibilty to say "I know what I want, please use the hint I configured".

Maybe it's not a VirtualBox bug, but I think it's an improvement that could be made by VirtualBox.

I'm open to other ideas.