virtualbox.org

I'm running a Linux guest under Windows 10 using Virtualbox 5.0.14 r105127. The guest is using virtualbox-guest-utils 5.0.14-dfsg-1.

My laptop has a 2736x1824 display and my external monitor is 2560x1440.

When I run the vbox frontend in fullscreen mode on my laptop monitor, everything works as expected. My guest can display on the host monitor in a 1-1 fashion.

However, when I run in fullscreen mode on the external monitor, I first don't get a proper picture, but just a couple of boxes with degraded graphics. If I now choose a main menu/view scale factor of 125%, I *do* get a picture, but fonts are small and fuzzy (due to not being 1-1 anymore but having a high-resolution guest display scaled down to 2560x1440). With a scale factor 100% I *can* get a picture if I choose a screen resolution of 2560x1440 in my guest, but the screen is then scaled to occupy only 50% of each linear dimension (=> fonts still fuzzy). I can now make the guest display fill the screen of the external monitor by choosing a larger scale factor, but will then get a 2-1-2 mapping which still makes the picture fuzzy.

What is all this weirdness about and how can I get a real 2560x1440 resolution on the external monitor?

Please post a VM log file. With the VM fully shut down, right click it in GUI. Select "Show Log" and save "VBox.log" (ONLY) to a zip file. Attach the zip here.

Please find the log attached to this post.

I started the VM, entered fullscreen mode, changed the scale to 100% (causing the window to cover 25% of the screen area as told before), all while the guest maintains a resolution of 2560x1440, then closed it down, saving the log.

It turns out that I had something called "custom scaling" set to 125% in the Windows 10 display settings.

When I turned this off, the screen resolution of the Virtualbox graphical frontend started to behave as expected.

I can now utilize the full 2560x1440 resolution of my external monitor from the guest.

However, now I can't get native 1-1 resolution on the laptop display. Instead of native 2736x1824, I get 1710x1140 in the graphical frontend.

Why does it need to be this complex? Shouldn't fullscreen with 100% scale factor always mean native resolution?

In no particular order :-

I see that you have selected a generic Linux template, and for a 2.6 kernel too. That is almost never correct. What is the actual distro?

You still have the GAs ISO mounted in the VM. It is good practice to eject this asap.

You have forked GAs installed: '5.0.14_Debian'. You need to get rid of these if you want support here. This could be especially tricky if you also tried to install the official GAs.

Thank you for your feedback!

mpack wrote:I see that you have selected a generic Linux template, and for a 2.6 kernel too. That is almost never correct. What is the actual distro?

It is 64-bit Debian stretch (testing) with a 4.3.3 kernel.

I have now switched to the Debian 64-bit template.

mpack wrote:You still have the GAs ISO mounted in the VM. It is good practice to eject this asap.

Ejected.

mpack wrote:You have forked GAs installed: '5.0.14_Debian'. You need to get rid of these if you want support here. This could be especially tricky if you also tried to install the official GAs.

I got rid of these and installed the official GAs.

No change---I can still not use native resolution on laptop display (but I can on external monitor). Still at 1710x1140 instead of 2736x1824.

I attach a new log for you.

To be really sure that I used the correct version of the GAs, I created a new virtual machine from scratch based on Debian 64-bit and re-installed GAs.

The problem remains, however.

Attaching new log.

Well, I think all you can do now is raise a BugTracker ticket. I use a desktop PC with one display, so I'm not in a position to reproduce your problem.

I researched the problem some more and created the following ticket:

https://www.virtualbox.org/ticket/15132

That ticket has problems.

You should use the established term "Fullscreen mode" if that is what your ticket is talking about. "Full resolution" is not accurate: you are changing the window size, not the resolution. Plus the VMs display is a simulation so has nothing to do with the "native resolution" of your monitor. These apparant irrelevances could make the devs skip over your ticket.

My understanding of your issue is that fullscreen mode doesn't work properly in a dual monitor setup. That's what should be said in the ticket.

mpack wrote:That ticket has problems.

You should use the established term "Fullscreen mode" if that is what your ticket is talking about. "Full resolution" is not accurate: you are changing the window size, not the resolution. Plus the VMs display is a simulation so has nothing to do with the "native resolution" of your monitor. These apparant irrelevances could make the devs skip over your ticket.

My understanding of your issue is that fullscreen mode doesn't work properly in a dual monitor setup. That's what should be said in the ticket.

Hmm... but doesn't my second sentence in the ticket explain what I mean?

I want the resolution of the simulated window (regardless if we describe this as DPI or as window size in fullscreen mode) to be equal to native resolution of the display, such that for each simulated pixel, there is one and only one real pixel corresponding to the simulated one.

Since our discussion, I have tracked down the problem to be related to a display scaling feature in Windows 10. For certain settings of this scaling (whether chosen automatically by Windows or manually by the user), fullscreen mode either doesn't work or gives you the wrong resolution (not native). The connection to having two monitors is that the automatic scaling of Windows either adapted to one or the other of the two screens... So, having two monitors isn't directly related to my problem, but is just one case which exposes it. (I didn't know this during our discussion but found out after a while.)

I hope the devs ask me for the clarifications they want. Or, you still have doubts?