Sikulix Error

I'm playing with RPA on a dynabook N40 with Ubuntu and Sikulix, but at first I got an error when executing commands that handle images such as find(). It seems I'm missing a module.

$ java -jar sikulixide-2.0.5.jar -r .
[error] App: command wmctrl is not executable, the App features will not work
[error] App: command xdotool is not executable, the App features will not work
[error] findWindow:
[error] error in command [wmctrl, -lpGx].

This is how it looks like. In this case, you can simply install them on Ubuntu.

sudo apt install wmctrl xdotool

Sikulix seems to have a policy of being very user-friendly (lol), so when you get an error like this, you may be surprised when your browser suddenly starts up and jumps to the Sikulix github site. There, you see.

• If you got here automatically,
• You got an error something ~~, right?　
• The solution is ~~.

They will kindly tell you how to solve the problem. It may be normal nowadays, but it is surprising that a program language can do this much for you at runtime.
However, in some cases, you may be running Sikulix stand-alone, or secretly (lol) behind the firewall of your company and accidentally connect to the outside using http, which may result in a security breach that you will be scolded later (lol). If you are running in such an environment, please be very careful (:-p).