Command line: Invalid commands should produce syntax error

[kanurag94]

Currently command line functionality in xaos is difficult to use, mostly since it doesn't produce any warning/error on use of wrong syntax. We should be able to start checking command syntax and produce warnings and help messages accordingly.

I am using a Ubuntu 20.04 install with Qt build from source

[kovzol]

I assume you mean the command line interface and also the commands that are available in the Action > Command... menu.

1. The command line interface already exists if you enter a command that cannot be recognized. But immediately after then the whole help is shown (that can be invoked by xaos -help). I think this is not very convenient, so maybe XaoS should not show more message than like this:

h:unknown function, please enter "xaos -help" to learn more on command line options

Note that currently the first part ("h: unknown function") is working, and printed to stderr. I think this is acceptable. Also, maybe we want to avoid printing other types of debug information. I am unsure if they are only available in the DEBUG build. For a DEBUG build this is OK.
2. I confirm that there should be some error message given if the command given in via the Action > Command... menu. The error message could be somewhat the same as shown via the command line interface. So, they should be handled in a somewhat unified way.

[kanurag94]

I am unsure if they are only available in the DEBUG build

Yes they are only available in DEBUG build.
I have done changes for 1 - c2bd042

I will try to work on 2 in next few days.

[kovzol]

Very good, thanks!