X11 stops rendering during automated testing while switched to different run level

Question

I am running automated tests on an app while recording the desktop for future analysis.

I am working from a standard Ubuntu Linux setup.

I would like to be able to switch to another user while these tests are running to continue working on other tasks.

When I switch to another user using a different virtual console logging in and starting a second x11 session using startx the screen recording of the X11 server running on Ctrl+Alt+F7 records nothing but a black screen.

I have discovered that this is because the X11 screen buffer stops rendering on none active run levels .

What configuration setting for X11 keeps will keep it rendering when switched away from that virtual console?

Patching and building X11 is not preferable but acceptable .

score 1 · Answer 1 · edited Apr 13 '17 at 12:36

1

Don't run your tests on an X server that displays to your hardware. Run them in an X server that “displays” to a virtual framebuffer that's just a chunk of memory, such as Xvfb. Xvfb is commonly used for testing GUI applications such as web browsers.

This won't work if your application needs to work closely with hardware features, e.g. because it needs 3D acceleration. But if this was the case your application wouldn't work when the X server isn't rendering anyway.

edited Apr 13 '17 at 12:36

Community

1

answered Jun 05 '15 at 00:12

Gilles 'SO- stop being evil'

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it is in fact using HW acceleration to render – Tegra Detra Jun 05 '15 at 00:15
@JamesAndino So what happens when you switch to another tty and X stops rendering? – Gilles 'SO- stop being evil' Jun 05 '15 at 00:18
the screen recording of the application just stops and goes blank , i have a little program that compares those recordings between test runs and looks for visual discrepancies . – Tegra Detra Jun 05 '15 at 00:19
@JamesAndino But not the application? How do you know that the problem is with the screen recording and not with the application? – Gilles 'SO- stop being evil' Jun 05 '15 at 00:19
the data output from the application is correct , points progress level etc . also silly but you can still hear the audio output . I found a short blurb about how x11 does not render when switched to another tty , but no further info after a fair amount of searching . – Tegra Detra Jun 05 '15 at 00:20
But how do you know that the application is still rendering and not just sending commands that are ignored by some low-level library when the display is “off”? – Gilles 'SO- stop being evil' Jun 05 '15 at 00:23
I would assume that in either circumstance there would be a configuration to ignore that "off" state – Tegra Detra Jun 05 '15 at 00:26
Another possible solution is to create a Virtual Machine, and record the output from the virtual machine. – eyoung100 Jun 10 '15 at 16:41
@eyoung100 That wouldn't help since the point is to use the hardware. – Gilles 'SO- stop being evil' Jun 10 '15 at 17:17

X11 stops rendering during automated testing while switched to different run level

1 Answers1