HI Arjen,
 I have learn plplot almost a week,I find some problem ,my APP is  WIN32 GUI APP,plplot seem to unfriendly with GUI app.The first  problem is the func "plio_fgets" in \src\plstdio.c;the func "plio_fgets" use "stdin";"stdin" can work fine in a CUI app.But in a GUI APP,how can i  send my string buffer to a console?because the "plio_fgets" just want to get user's option(1,2,3 etc) and set the "response" parameter ,so i want to modify the code and don't
call "plio_fgets",Then i built plplot again ,i get a new "plplotd.dll"and "plplotd.lib",but i find the "plplotd.dll" still
contain the "plio_fgets",i guess may be the cmake ignore my modification; so i have to use "hook",I spent three
day to make "hook" work fine ,then  i see the math graph again;but when i click the "open"button again,oh my god,it close my app ;so i decide debug it again ,and i find the error,it's the func "plD_init_wingcc"in "wingcc.c";
when CreateWindowEx call twice,second time the CreateWindowEx will return null;so CreateWindowEx fails.i try to solve it ,but after 2 days .i still can't have any idea about it .Can you test x02c.c in you GUI app,you use a button,and click it twice;Thank you