Java and GTK (native code)

[arvigeus]

Hello! I'm trying to build a GUI for my java app and compile with gcj (to native code). I started googling and found 3 possibilities: Java-Gnome, Gnome-GCJ and libswt. Unfortunately, Java-Gnome is not compatible with gcj and Gnome-GCJ is, but is no longer maintained. The third option, libswt, I could not find any clear information what is it and how it works. Can you enlighten me a bit more about the subject?

[Cabhan]

So I don't know anything about using it with gcj, but I've used SWT before. It's basically a GUI toolkit developed by the Eclipse Foundation, and it is what Eclipse uses. I originally came to it because it uses native libraries for its graphics, and it looked a lot nicer than Swing back in the day (this was when Swing on Linux looked like Gtk 1.x, which is really ugly).

The SWT page is at:
SWT: The Standard Widget Toolkit

You may also want to look at JFace, which I've never used, but supposedly makes using SWT easier:
JFace - Eclipsepedia

[arvigeus]

I was talking about libswt dot sourceforge dot net
Anyway, same principles probably are applied for both swt's. Anyone having experience with gcj compiling this?

[Rubberman]

Some indication of the errors you are getting might be helpful...

[Cabhan]

I'm with Rubberman: clarification of your errors would help. Assuming that you've written your Java code with SWT, it should be as simple as passing -lswt to the linker in order to make it work with libswt.so, as you would do with any shared library.

[arvigeus]

Actually, I don't know from where to start at all. I will try reading the eclipse's manual of how to build an app, but would the code be compatible with libswt? Also, what do I have to pass to gcj to detect the needed shared objects (probably some classpath option, but I never did that before)?

I'm sorry for being so unhelpful, but I never done something like that before and I'm still disoriented what to do.

[arvigeus]

I made some progress, now I have an error
Here is the sample code:

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

public class Snippet143 {

public static void main(String[] args) {
	Display display = new Display ();
	Shell shell = new Shell (display);
	Image image = new Image (display, 16, 16);
	final Tray tray = display.getSystemTray ();
	if (tray == null) {
		System.out.println ("The system tray is not available");
	} else {
		final TrayItem item = new TrayItem (tray, SWT.NONE);
		item.setToolTipText("SWT TrayItem");
		item.addListener (SWT.Show, new Listener () {
			public void handleEvent (Event event) {
				System.out.println("show");
			}
		});
		item.addListener (SWT.Hide, new Listener () {
			public void handleEvent (Event event) {
				System.out.println("hide");
			}
		});
		item.addListener (SWT.Selection, new Listener () {
			public void handleEvent (Event event) {
				System.out.println("selection");
			}
		});
		item.addListener (SWT.DefaultSelection, new Listener () {
			public void handleEvent (Event event) {
				System.out.println("default selection");
			}
		});
		final Menu menu = new Menu (shell, SWT.POP_UP);
		for (int i = 0; i < 8; i++) {
			MenuItem mi = new MenuItem (menu, SWT.PUSH);
			mi.setText ("Item" + i);
			mi.addListener (SWT.Selection, new Listener () {
				public void handleEvent (Event event) {
					System.out.println("selection " + event.widget);
				}
			});
			if (i == 0) menu.setDefaultItem(mi);
		}
		item.addListener (SWT.MenuDetect, new Listener () {
			public void handleEvent (Event event) {
				menu.setVisible (true);
			}
		});
		item.setImage (image);
	}
	shell.setBounds(50, 50, 300, 200);
	shell.open ();
	while (!shell.isDisposed ()) {
		if (!display.readAndDispatch ()) display.sleep ();
	}
	image.dispose ();
	display.dispose ();
}
}

In order to compile it, I run: (found on the net)

gcj -fjni --classpath=/usr/share/java/swt.jar -c Snippet143.java -o Snippet143.o

gcj -fjni -c /usr/share/java/swt.jar

gcj -shared -fPIC -fjni -o libswt.o swt.o -o libswt.so

gcj --main=Snippet143 -o Snippet143 Snippet143.o -L. -lswt

And I got when trying yo finally run it:

error while loading shared libraries: libswt.so: cannot open shared object file: No such file or directory

[Rubberman]

It's saying that it can't find the shared library file libswt.so.

[arvigeus]

I found that file: /usr/lib/gcj/swt-gtk-3.5.1.jar.so
It's probably the one I would like to link to instead of making my own libswt.so file. What to change in the compile commands to do it?

Edit: Wrong file. Seems it's not to be working. Is there some package that is providing libswt.so? (or else I should move it to lib)