Slow Performance in VirtualBox

[DavidLudwig]

While doing testing for Linux, it was noticed that the SDL2 backend could be slow, if and when:

1. running in a VirtualBox VM
2. using the "opengl" SDL_Renderer backend. Using the "software" renderer could alleviate this, in some cases.

[rickyzhang82]

You need to install guest addition in guest Linux OS. See setup

[DavidLudwig]

I could see the guest addition helping, however, it was much slower than with the SDL1 backend. I'd like the SDL2 backend to be usable, if at all possible, regardless of whether special, guest VM drivers are installed.

Change 50986dc does seem to help, but I'd like to test that a bit further, before closing this case.