Use log facade in testbed2d.

[ThierryBerger]

To illustrate what I'm suggesting with issue #128

I can make the same update for testbed3d if you're interested.

[sebcrozet]

Thanks, that's a good suggestion!

I can make the same update for testbed3d if you're interested.

Definitely interested!

[ThierryBerger]

Glad you like it.

Issues to take into account :

• When running the examples, we lose the logs (as no log implementation is set).

I suggest to choose the most minimal one and add it as a dependency of all examples. simple-logger or env-logger are both good candidates.

I chose env_logger arbitrarily (I like their documentation most)

I will update the pull request with it.

Also, by default, logs are set to a minimum, as per env_logger documentation :

Log levels are controlled on a per-module basis, and by default all logging is disabled except for error!. Logging is controlled via the RUST_LOG environment variable. The value of this environment variable is a comma-separated list of logging directives. A logging directive is of the form:

So to enable them back, you have to invoke the examples like that:
RUST_LOG=nphysics_testbed2d cargo run --bin balls2

Perhaps the nphysics documentation should reflect that.

[sebcrozet]

Thank you for your suggestion here. I am going to close this PR in favor of #143 which:

• Enables the log facade only if the log feature is enabled.
• Does not change the examples (which keep using the default behavior based on println).