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GEF SVG export in JWT: a newcomer’s rocky ride to Eclipse
- 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