I've not used those programs but the hatch patterns they use shouldn't be too difficult to mimic.
They are mostly EXACTLY the same patterns as Autocad.
They are NOT (PAT or SHX) files.
They CAN NOT be added to or deleted from.
They are embedded in the application code.
I have been sent and told approximately what I must do using a 'work around' to take my desired pattern object(s) and convert it to XML file format
and then I will be able to do area fills with that data as part of what they call 'advanced stylization', although it seems to be very primitive.
The price of OPENSOURCE.....and of course a similar feature DOES exists and is better supported in the pay version.