This document discusses GEF4, a project to develop a next generation version of the Graphical Editing Framework (GEF) and Zest projects. It provides an overview of the status and goals of the GEF4 Geometry and Graphics components, which aim to modernize the underlying technologies while maintaining a stable API. The document invites the reader to get involved by providing feedback, trying early versions, and contributing code or other assistance to help guide the future development of GEF4.

1. Share and Enjoy!
Alexander Nyßen
itemis AG
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2. GEF 3.x / Zest 1.x
• Mature project with quite long history
• Base technology with lot's of users (direct & indirect through
GMF/Graphiti)
• Stable API, no breaking API changes since 2004 (GEF 3.0)
• Ready for CBI (migration to Git, Maven/Tycho completed)
• But API is organically evolved and there are ~400
bugzillas, out of which several require to break it

3. SomeTopics for a Renewal
• Re-thinking current componentization
• Support for the E4 application model
• Support for rotation and other transformations
• Support for curved connections
• Support for other rendering platforms than SWT
• Multi-touch gestures support
• Revision of the command framework
• Revision of connection handling (clipping container)
• Various renamings and restructurings on the detail level...

4. Zest 2 (since 2010)
• A provisional Zest 2 component was initiated in 2010, to
develop the next generation Zest API.
• Goal was to develop a new version of Zest in parallel to the
maintenance of Zest 1.x., with an - up to the final
graduation - provisional API
• Sources were intended to be placed in its own Zest2 Git
repository, results were published separately via Eclipse
Marketplace.

5. GEF4 (since 2011)
• GEF4 was initiated - in analogy to Zest 2 - to develop the next
generation Draw2d and GEF (MVC) API.
• Similar to Zest2, development was intended to take place in
parallel to maintenance of Draw2d / GEF (MVC) 3.x
• Initial plans (prior to 3.8):
• Create new double-precision Geometry API before Juno
release.
• Start to migrate the Draw2d and GEF (MVC) code base on a
step-by-step basis afterwards.

6. GEF4 + Zest 2 = GEF4
Modified plan:
Unification of both approaches after Juno!

7. GEF4 - A Unified Approach
• A unified approach with a shared code base and a
common namespace (org.eclipse.gef4) for all plug-ins.
• Advantages:
• Clear distinction between GEF proper as the production
component and GEF4 as the provisional one
• Chance to not only refactor GEF components but the
componentization itself, which is only "historically" justified.

8. GEF4 - Status Quo
• GEF4 Geometry component was initiated in 2011, work has been
finalized with the Juno release:
• Functionally complete (at least for now)
• 344 JUnit tests, ~77% instruction coverage
• GEF4 Graphics component was initiated directly after Juno and is
currently under work:
• Functionally nearly complete for SWT/AWT, intended JavaFX adoption
about to start
• Still limited tests and quite a bit of adjustment needed w.r.t. "platform-
specific" issues of SWT

9. GEF4 - Status Quo (continued)
• GEF4 Zest was transferred to Git repository (and update-
site) but not yet adopted:
• Zest2 plug-ins were renamed to org.eclipse.gef4.zest.*
• Dependencies on Draw2d 3.x still have to be factored out

10. GEF4 Geometry
• No distinction in low and high precision, but just a single double-precision
API (with built-in imprecision for comparisons).
• Different geometric abstractions for different purposes:
• Euclidean (Vector, Straight,Angle)
• Projective (Vector3D, Straight3D)
• Planar (Point, Dimension, Line, QuadraticCurve, CubicCurve,
BezierCurve, Polyline, PolyBezier, Ellipse, Rectangle, Pie,Arc, Polygon,
CurvedPolygon, RoundedRectangle, Ring, Region, Path)
• Conversions to/from AWT and SWT (and between them)

11. GEF4 Planar Geometry - Features
• Support for "non-standard" geometries:
• Arbitrary Bezier curves, curved polygons
• Approximation via BezierCurves & Interpolation via PolyBeziers
• Characteristics-related core abstractions (IGeometry, ICurve, IShape,
IMultiShape)
• Construction-related base-classes (AbstractRectangleBased-
Geometry,AbstractPointListBasedGeometry,...)
• Direct support for affine transformations (ITranslatable, IScalable,
IRotatable)
• No direct SWT dependencies (SWT-related conversions bundled in
optional plug-in)

12. GEF4 Planar Geometry - Overview

13. GEF4 Planar Geometry - Abstractions

14. GEF4 Planar Geometry - Base Classes

15. GEF4 Geometry - Examples

16. GEF4 Geometry - Sample Code
// Bezier approximation of curves
BezierCurve[] fromCurve = curve.toBezier();
BezierCurve[] fromShape = shape.getOutline().toBezier();
ICurve[] fromPolyShape = polyShape.getOutlineSegments();
List<BezierCurve> beziers = new ArrayList<BezierCurve>();
for (ICurve c : fromPolyShape)
beziers.addAll(Arrays.asList(c.toBezier()));
// PolyBezier interpolation
PolyBezier interpolation = PolyBezier.interpolateCubic(p0, p1, p2, p3, ...);
// support for affine transformations
Polygon rhomb = new Rectangle(10, 10, 10, 10).getRotatedCCW(Angle.fromDeg(45));
PolyBezier slanted = new Ellipse(100, 100, 100, 50).getRotatedCCW(Angle.fromDeg(30));
Ring rotatedClippingArea = region.getRotatedCCW(Angle.fromDeg(300));

17. GEF4 Graphics
• Support for rendering (planar) geometries, images, and text
on an underlying Canvas/Graphics
• Key abstractions (Font, Image, Color) and transparent
support for multiple widget toolkits (SWT,AWT, JavaFX*)
• Save push/pop/restore and get/set of graphics state
• Combinations of advanced graphics features like xor-mode,
patterns (color, gradient, image), affine transformations, etc.
• Extensible image processing support (Pixel-Filter, Channel-
Filter, Convolution-Filter)
*) Graphics based on JavaFX Canvas API already prototyped byTom Schindl

18. GEF4 Graphics - Features

19. GEF4 Graphics - Overview

20. GEF4 Graphics - Examples

21. GEF4 Graphics - Sample Code
// prepare geometries
final Ellipse ellipse = new Ellipse(50, 50, 350, 200);
final Rectangle rectangle = new Rectangle(100, 160, 125, 220);
final Polygon triangle = new Polygon(260, 170, 190, 300, 330, 300);
// prepare colors
final Color red = new Color(255, 0, 0);
final Color darkRed = new Color(128, 0, 0);
final Color blue = new Color(0, 0, 255);
final Color green = new Color(0, 255, 0);
final Color darkGreen = new Color(0, 128, 0);
g.setLineWidth(4);
g.pushState(); // save the current set of properties on the stack
g.setFill(red).setDraw(darkRed).setDashArray(25, 10);
g.fill(ellipse).draw(ellipse.getOutline());
g.restoreState(); // restore the previously saved properties
g.setFill(blue).setLineJoin(LineJoin.ROUND).setLineCap(LineCap.ROUND);
g.fill(rectangle).draw(rectangle.getOutline());
g.popState(); // removes the previously saved properties from the stack
// and enables the properties that were set in advance
g.setFill(green).setDraw(darkGreen).setLineJoin(LineJoin.MITER);
g.fill(triangle).draw(triangle.getOutline());

22. GEF4 Graphics - More Sample Code
• Java2D:
• GEF4 Graphics (Java2D & SWT):
g2d.translate(50, 50);
g2d.setPaint(new RadialGradientPaint(new Point(50, 50), 50, new Point(
40, 40), new float[] { 0, .5f, 1 }, new Color[] {
new Color(255, 255, 255), new Color(255, 0, 0),
new Color(0, 0, 0) }, CycleMethod.REFLECT));
g2d.fill(new Rectangle(0, 0, 200, 200));
g.translate(50, 50);
Ellipse ellipse = new Ellipse(0, 0, 100, 100);
g.setFill(new Gradient.Radial(ellipse, ellipse
.getCenter().translate(-10, -10), CycleMode.REFLECT)
.addStop(0.0, new Color(255, 255, 255))
.addStop(0.5, new Color(255, 0, 0))
.addStop(1.0, new Color(0, 0, 0)));
g.fill(new Rectangle(0, 0, 200, 200));

23. GEF4 - Outlook (Mid-Term)
• GEF4 Layouts is planned:
• Data model for layout computations (based on Draw2d/
Zest DirectedGraphLayout)
• Set of layout algorithms based on it (Draw2d & Zest)
• GEF4 'Glyphs' is planned:
• Figures/Shapes abstractions inspired by Draw2d, SVG, and
JavaFX (SceneGraph)
• Intended as replacement of Draw2d 'core'

24. GEF4 - Outlook (Long-Term)
• Adoption of migrated Zest components to new GEF4
Geometry, Graphics, Canvas, Layouts components
• Migration of remaining Draw2d/GEF (MVC) code base,
including re-modularization and adoption

25. Share & Enjoy - Please get involved!
• Evaluate and Provide Feedback!
• Try out early snapshots!
• Report bugs, report enhancement requests!
• Contribute!
• Participate in discussions (bugzilla, mailing list)
• Supply patches

26. ThankYou! Questions?
http://wiki.eclipse.org/GEF/GEF4