Re: -Djava.awt.headless=true and Gtk...

On Wed, 2005-08-03 at 18:44 -0400, Martin Cordova wrote:
> "GDK is basically a wrapper around the standard Xlib function calls.
> If you are at all familiar with Xlib, a lot of the functions in GDK
> will require little or no getting used to. All functions are written
> to provide an way to access Xlib functions in an easier and slightly
> more intuitive manner. In addition, since GDK uses GLib (see below),
> it will be more portable and safer to use on multiple platforms."
> 
> >From its description, GDK on Linux relies on XLib.

On GNU, perhaps.  But GDK is drawing primitives ported to non-X GUIs as
well, and there's no point to duplicating that work.

Blame eager static initializers.  As stated by
native/jni/gtk-peer/gnu_java_awt_peer_gtk_GtkToolkit.c:155, gtk_init
must be called before any other GTK calls; the easiest way to ensure
this is with a static initializer.  Then, note the static initializer at
gnu/java/awt/peer/gtk/GtkToolkit.java:109, which calls the
Java_gnu_java_awt_peer_gtk_GtkToolkit_gtkInit function very near the
aforementioned C file position, which in turn calls gtk_init, which
itself tries to connect to the X server and exits the process if it
fails.  This is triggered simply by loading the class.

> Does this means that there is no way to use a headless environment
> w/Classpath (without graphics desktop running on server)??

Many applications don't load any classes that load GtkToolkit, and these
can be run on Classpath-using JVMs as-is.  Apps that refer to, or
especially initialize instances of, AWT/Swing classes force a call to
gtk_init.

Hacking eager initializers to be lazy is hard work.  The easiest fix I
can think of with my limited knowledge of GUI drawing is a Java-based
solution: make a "dummy" AWT peer that only pretends.  This would still
be some effort, so Etienne Gagnon's earlier suggestion of asking the GNU
Classpath folks is probably best; they may know something we don't.

In the meantime, the best hack I can think of is to fake out libgtkpeer
by starting a VNC server running twm (or nothing if you can get that to
work), and telling sablevm to use its display.  Your system constraints
may prevent this, however.

-- 
Stephen Compall

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