(by Michael Froehlich, 1994-11-09)

This directory contains an example application which can be connected to the 
application interface of the interactive graph visualization system daVinci. 
Refer to the daVinci user manual and the documented source code (in file 
application.c) for further details.

Use 'make' to compile this application. If you are not using a standard
OpenWindows installation (in /usr/openwin), then you must edit the Makefile
to specify the correct library paths. In the directory there is a compiled 
binary of the example application for Linux.

You can connect this application to daVinci by using two different methods: 
    (1) Either you start the application from daVinci with menu
        'File/Connect Application...' by specifying the filename 
        and full directory path of the application in the subwindow or
    (2) you start daVinci from the application by pressing button 
        'Connect daVinci...'. Afterwards, you have to specify the name and 
        full directory path of daVinci and press 'Connect'.
    	
The application has two text subwindows. In the upper one you can edit 
messages which should be send to daVinci's application interface. After 
pressing 'Send Message', the whole text content of this subwindow is sent 
to the visualization system. You can find some examples for commands in 
the file command_examples.txt in this directory. More informations about 
daVinci's application interface can be found in the appendix B of the user 
manual. In the lower text area you can see the answers from daVinci. 

CAUTION: you can only send messages to daVinci which are compliant to the 
command grammar found in figure 5 (appendix B.3) of the user manual. Other
commands to the interface have be avoided. They are forcing an error 
message answer:

	communication_crash("syntax error in incoming message").
	
A typical problem is a warning message from the application at startup 
time such as this linker warning:

	ld.so: warning: /usr/openwin/lib/libX11.so.4.3 has older revision 
	than expected 10
	
This message is printed on stdout, i.e. it is sent to the application 
interface after you connect the application from daVinci. Of course this 
warning is not a command of the interface, so the communication fails. You 
have to make sure that the application is not reporting warnings or error 
messages on stdout (otherwise you have to use a different file descriptor
than stdout for communication). You can check this condition by starting 
the application alone from a shell. After starting the application, nothing 
should be displayed unless you press the 'Send Message' button.


