A walkthrough about a pragmatic bug resolution by a junior Eclipse contributor: SVG diagram export in Java Workflow Tooling. First presented in the Eclipse Juno Democamp in Grenoble, on the 13th ofJuno, 2012.

1. GEF SVG export in JWT
A newcomer’s rocky ride to Eclipse
Eclipse DemoCamp Grenoble 2012
Yoann Rodière (Open Wide, FR)
thanks to Marc Dutoo (Open Wide, FR)
Confidential | Date | Other Information, if necessary
© 2002 IBM Corporation

2. SVG export in JWT
• Bug #327563 (since 2010)
• Why export?
– JWT (Java Workflow Tooling) is all about modeling
– Modeling is all about communication
– Diagram export, i.e. communicating one's work, is
unavoidable!
• Why SVG?
– (besides throwing a poor newbie in heavily mined territory)
– Indeed, JWT already has image export : PNG, JPG
– … but tell that to an image professional and he'll laugh!
– Users need a scalable, “zoom-able”, vector format
Eclipse Foundation, Inc. | © 2012 by the Open Wide. Made available under the EPL v1.0 2

3. License headaches ahead
• Obviously, we'll need a library
• Unfortunately, no such feature in GEF
• Image Export Plugin - Thomas Mayer
– Supports PDF, EPS, … SVG!
– GPL'd
“The Eclipse Public License is similar to the Common Public License”
“[...] its weak copyleft and choice of law clause make it incompatible with the
GNU GPL”
Copyright © 2011 Free Software Foundation, Inc.
http://www.gnu.org/licenses/license-list.html#SoftwareLicenses
Well, there's always a way to argue, but...
Lawyers are dangerous!
Eclipse Foundation, Inc. | © 2012 by the Open Wide. Made available under the EPL v1.0 3

4. And now what?
• Let's get back to basics
• How to create SVG files?
– Apache Batik
– Already in Orbit! => Faster CQ re-approval by the IP team
• Problem: Batik targets AWT
– Eclipse => SWT
– We need a bridge!
Eclipse Foundation, Inc. | © 2012 by the Open Wide. Made available under the EPL v1.0 4

5. Software from the back of the attic
• Holongate: a bridge between Java2D (AWT) and
Draw2D (SWT)
– Not in Orbit
– Some strange JNI, system-dependent code in their repo
– Old
• Started in 2004
• Last updated in 2007, Eclipse 3.1 (is it still alive?)
What's unknown is dangerous!
– Lawyers ahead!
– Compatibility issues (OS, Eclipse 3.8 vs 3.1)
– Old dependencies
• Obsolete versions?
• Version conflicts?
– … with Juno release ever closer (and IP Team ever busier)!
Eclipse Foundation, Inc. | © 2012 by the Open Wide. Made available under the EPL v1.0 5

6. Getting around APIs (1)
• Another bridge: GMF (ever heard about
GMF?)
– Class GraphicsToGraphics2DAdaptor
– But...
• Aims at implementing SVG export for GMF only
• Therefore internal... how selfish!
What you can't control is dangerous!
– Relying on private APIs is relying on chance
– Know about Murphy's Law? ;)
• As Einstein said, “**Yearly releases** don't play dice”
Eclipse Foundation, Inc. | © 2012 by the Open Wide. Made available under the EPL v1.0 6

7. Getting around APIs (2)
• So, game over?
• No! We could go the strict, right way...
– Use the public API where it exposes SVG export services
– Which would mean using GMF and not only GEF
• … or the quick, practical way
– Copy/paste what we need
– Add comments to point to the original code
– Keep all copyright notices
– File a CQ
What does not change... is quite safe!
– Code is known & already running
– No API change to fear
– Complete control over the code to fix bugs
• e.g. implement unsupported operations such as setTextAntialias
– Switch to GMF API is straightforward if the classes are ever made public
Eclipse Foundation, Inc. | © 2012 by the Open Wide. Made available under the EPL v1.0 7

8. What's next?
• Clean up the mess
– “Solution” doesn't mean “definitive”; ours was quick but not
perfect
– Assess Holongate (now we've got the time)
– Ask GMF for an API extension
• Provide other exports...?
– See later with Marc ;)
Eclipse Foundation, Inc. | © 2012 by the Open Wide. Made available under the EPL v1.0 8

9. Conclusion
• For a junior Eclipse contributor
– Beware of licenses
– Beware of unknown software
– Beware of unstable APIs (internal... or not)
– Believe in iterative development ;)
• For a senior Eclipse contributor
– Beware of junior Eclipse contributors!
Eclipse Foundation, Inc. | © 2012 by the Open Wide. Made available under the EPL v1.0 9