When you have Flutter app performance problems, try Profile Mode

Today I learned that for several reasons, Flutter Debug mode may be significantly slower than Production mode. As just one reason, Debug mode is compiled using JIT while Production mode uses AOT. You can read more about the reasons on the Flutter UI Performance page.

A very important note on that page is that if you’re using a real hardware device (as opposed to an emulator), you can run your code in Profile mode like this:

Scala REPL: There were deprecation warnings, re-run with -deprecation alvin March 26, 2013 - 5:26pm

Whenever I used to get the Scala REPL warning message, "There were deprecation warnings, re-run with -deprecation", I used to have to restart the REPL with the -deprecation flag to see the warning message, like this:

$ scala -deprecation

That works, but sadly, you had to lose your entire REPL session to run it.

Use :warnings

Thanks to the Scala gods, this is no longer necessary in Scala 2.10 (and newer). Now, when you get the REPL deprecation warning message, like this:

How to put SBT into offline mode with a command line setting

Scala SBT FAQ: How do I put SBT into offline mode so I can use it while working on an airplane, or any other location where I don't have a WiFi connection?

Use an SBT command like this to compile and run a project from your operating system command line:

$ sbt "set offline := true" run

I used this command a lot recently when I didn't have internet access, and I had to keep SBT from trying to reach out to the internet all the time.

How to start a Mac in safe mode

Mac question: Something just went wrong, and I need to start my Mac (or iMac) in safe mode, or something like safe mode? Can this be done on a Mac?

Answer: Yes, Mac computers support a "safe mode" boot process. Here are the steps needed to start your Mac/iMac in safe mode:

Error message: mv cannot unlink remove file, operation not permitted

I got this Unix/Linux error message today "mv: cannot unlink '/tmp/forms-1.2.1.jar': Operation not permitted" when trying to move (mv) the file forms-1.2.1.jar from the /tmp directory to another directory. The full error output looked like this: