Description:

Although this could've been reported before (I did several searches which turned nothing of relevance up), opening a command block and then leaving full screen will instantly delete all the command contents of a command block. (Note: You should be on a mac)

Reproduction:

Step #0:

Get a command block, you should have OP level 2+/singleplayer cheats and Creative Mode.

Step #1:

Put any command into a command block, it works as long as any text is entered in a command block.

Step #2:

Move out of fullscreen. (Not using the provided option; on mac, you should be able to leave fullscreen by pressing the third button on the top right)

Step #3:

You will see that all the contents of the command block have been deleted.

Notes:

I've searched for various things, this could possibly duplicate a bug(s) while searching "Window resize".