how to draw directed edges with "IGraphContentProvider"? - eclipse-rcp

Question

I am using ZEST and RCP to build a graph visalization tool. I used IGraphContentProvider and the LabelProvider for drawing the graph.
How can I draw a directed edge between two nodes using IGraphContentProvider?

Answer 1

Late answer, but I've just something similar:
You may do this, by providing a IEntityConnectionStyleProvider. It has a method called getConnectionStyle(src, dest). You can return the costant ZestStyles.CONNECTIONS_DIRECTED there, if all the connections are directed. Otherwise, you have to decide based on the source and destination, wether to draw a directed edge.
You may also want to look at IGraphEntityRelationshipContentProvider. With that content provider you can just add objects to the graph and later on decide which are connected.

Answer 2

Not a Zest expert, but a IGraphContentProvider seems limited to access the underlying obejct of a given relationship.
The getSource() and getDestination() methods will help a viewer like a Graphviewer, from AbstractStructuredGraphViewer view the edge defined by those "source-Destination" couples.
See this example for instance.
/*******************************************************************************
* Copyright 2005-2007, CHISEL Group, University of Victoria, Victoria, BC,
* Canada. All rights reserved. This program and the accompanying materials are
* made available under the terms of the Eclipse Public License v1.0 which
* accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors: The Chisel Group, University of Victoria
******************************************************************************/
package org.eclipse.zest.core.examples.jface;
import org.eclipse.jface.viewers.LabelProvider;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.zest.core.viewers.GraphViewer;
import org.eclipse.zest.core.viewers.IGraphContentProvider;
import org.eclipse.zest.layouts.LayoutStyles;
import org.eclipse.zest.layouts.algorithms.SpringLayoutAlgorithm;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
/**
* This snippet shows how to use the IGraphContentProvider to create a graph with Zest.
* In this example, getElements returns 3 edges:
* * Rock2Paper
* * Paper2Scissors
* * Scissors2Rock
*
* And for each of these, the source and destination are returned in getSource and getDestination.
*
* A label provider is also used to create the text and icons for the graph.
*
* #author Ian Bull
*
*/
public class GraphJFaceSnippet2 {
static class MyContentProvider implements IGraphContentProvider {
public Object getSource(Object rel) {
if ("Rock2Paper".equals(rel)) {
return "Rock";
} else if ("Paper2Scissors".equals(rel)) {
return "Paper";
} else if ("Scissors2Rock".equals(rel)) {
return "Scissors";
}
return null;
}
public Object[] getElements(Object input) {
return new Object[] { "Rock2Paper", "Paper2Scissors", "Scissors2Rock" };
}
public Object getDestination(Object rel) {
if ("Rock2Paper".equals(rel)) {
return "Paper";
} else if ("Paper2Scissors".equals(rel)) {
return "Scissors";
} else if ("Scissors2Rock".equals(rel)) {
return "Rock";
}
return null;
}
public double getWeight(Object connection) {
return 0;
}
public void dispose() {
}
public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
}
}
static class MyLabelProvider extends LabelProvider {
final Image image = Display.getDefault().getSystemImage(SWT.ICON_WARNING);
public Image getImage(Object element) {
if (element.equals("Rock") || element.equals("Paper") || element.equals("Scissors")) {
return image;
}
return null;
}
public String getText(Object element) {
return element.toString();
}
}
static GraphViewer viewer = null;
/**
* #param args
*/
public static void main(String[] args) {
Display d = new Display();
Shell shell = new Shell(d);
shell.setText("GraphJFaceSnippet2");
shell.setLayout(new FillLayout(SWT.VERTICAL));
shell.setSize(400, 400);
viewer = new GraphViewer(shell, SWT.NONE);
viewer.setContentProvider(new MyContentProvider());
viewer.setLabelProvider(new MyLabelProvider());
viewer.setLayoutAlgorithm(new SpringLayoutAlgorithm(LayoutStyles.NO_LAYOUT_NODE_RESIZING));
viewer.setInput(new Object());
shell.open();
while (!shell.isDisposed()) {
while (!d.readAndDispatch()) {
d.sleep();
}
}
}
}