well frietfriet has the answer again
by studying the html source of the product page I can see in the form that there is an input
field for every required option. the name of the field is ‘options’ for the option that
I have added (a string).
so I can add a product to the shopping cart with the design name set like this:
I didn’t get much help from the board visitors but fortunately I can study the source code of magento
which is the ultimate user guide.
long live opensource!