LessTalk diagram applet: Code

Code

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LessTalk diagram applet by Mark Paschal <markpasc@mindspring.com>

Download (zip)

LessTalk allows web site visitors to view and edit simple geometric diagrams in a Wiki-like fashion. It was designed primarily for use with Hello Wiki as a plug-in resource. Its features include:

Line, Rect, Ellipse, Arrow, and Text components
Can save documents to PNG images for display without the applet

Its missing and anti-features include:

Non-existent security in the lt.pl script
Carriage returns in Text components are not correctly handled
XML used in saving documents is not 'real' XML (ie, no use of pcdata inside tags or tags inside tags)
Still split into display and edit applets, even though edit applet can post PNG files to the server
Requires Java 1.3 (maybe only 1.2) to run

The applet is given just the loading param like so:

<param name="loadFrom" value="lt/filename.xml">

In edit mode, the applet submits XMLesque LessTalk documents to the accompanying lt.pl script via HTTP POST. The lt.pl script has no security whatsoever--anyone could POST anything to it and have it saved on the server as whatever, in the directory for the XML data.

<param name="loadFrom" value="lt/filename.xml"> <param name="saveTo" value="lt.pl?lt/filename.xml">

Since the applet requires versions of Java not usually found in common browsers, the applet can also send a uuencoded PNG file representing the diagram to the lt.pl script. The lt.pl script can uudecode these (with the Convert::UU module from CPAN installed somewhere, anyway) into the directory where the XML data is.

<param name="loadFrom" value="lt/filename.xml"> <param name="saveTo" value="lt.pl?lt/filename.xml"> <param name="saveImage" value="lt.pl?lt/filename.png">

The LessTalk diagram applet includes the com.ice.convert.UUEncoder class available at Giant Java Tree and Copyright 1997 by Matthew Hixson and Mark Spadoni; the com.keypoint.PngEncoder class by J. David Eisenberg available under the GNU Lesser GPL; and unmodified portions of com.microstar.xml, the free Ælfred XML library. As I understand the given licenses, my redistribution is in compliance; if it is not, please email me at markpasc@mindspring.com.