Follow XDG Base Directory specification on Linux

[erlisdhima]

By default the Arduino IDE creates a ~/.arduino15.

First issue, its on the $HOME dir. Ideally the XDG Base Directory specification must be used.
Second, the directory naming is specific to some version? Why not just .arduino ?

Finally, the files/directories inside it are all in one place.

$ ls ~/.arduino15
cache
library_index.json
library_index.json.sig
logs
package_index.json
package_index.json.sig
preferences.txt

As per the specification, this should be something like below...

Config files go into $XDG_CONFIG_HOME
From all the files, only preferences.txt has configs.

Cache files go into $XDG_CACHE_HOME
In this case it should be the cache directory.

actions history (logs, history, recently used files, …) go into $XDG_STATE_HOME
Here I'm assuming everything else from that directory are state files, and the logs directory, well, for logs.

[erlisdhima]

I found its doing this for all platforms.

Arduino/arduino-core/src/processing/app/Platform.java

Lines 77 to 81 in 57a931c

	public File getSettingsFolder() throws Exception {
	// otherwise make a .processing directory int the user's home dir
	File home = new File(System.getProperty("user.home"));
	File dataFolder = new File(home, ".arduino15");
	return dataFolder;

Since java doesn't have a way to get the XDG dirs directly, I found this example https://github.com/omajid/xdg-java/blob/master/src/main/java/org/freedesktop/BaseDirectory.java

That does not include $XDG_STATE_HOME though, and it will need to be added.

[per1234]

Closing as duplicate of arduino/arduino-ide#1514