Webkit & 4gl advice

I have a client that has a large legacy program (>200,000 lines of code) with more than 250 input and output screens all character based. They need to upgrade their product to a graphic user interface. We are looking at the feasibility of using web browser and rewriting i/o screens for web/cgi interface and leaving the core application intact running as cgi application on web server. My questions have to do with conversion of the existing 4gl code. User interface has been done using high level key words ( for some type of character based screen manipulation?). The keywords used are MENU (COMMAND), PROMPT, ERROR, DISPLAY FORM, MESSAGE, INPUT BY NAME, etc... I have downloaded the webkit and looked at the examples. All i/o there is done with icgi_print_text and icgi_getvalue calls. I have experience with cgi and html code, and am a newbie to 4gl. There obviously is a difference between the low level print/get cgi routines and the high level screen manupulation commands. Is there a cgi equivalent for the high level commands? Are there functions or macros available that can be used as a substitute for the high level commands? Ideally, the code would support both character based i/o for the current installed customer base and html based i/o for using browsers for new graphic GUI. Any advice? or pointers? Please share your experiences and opions. Thanks Herman Watson herman@honordesign.com