Function diagnose 

pub fn diagnose() -> DiagnosticReport

Finds the GPU the way a window would and describes it, along with the machine and the build, without showing anything. For a command line option such as --diagnostics, which still answers when a window would not open or would be too slow to use. Printing the result gives text to paste into a bug report.

Call it instead of running the app: a process has only one event loop.