<AWT Dev> RFR: 8198649 : Switch AWT/Swing's default GTK version to 3

[Kevin Rushforth]

This looks fine to me. I checked FX / Swing interop and it works as 
expected. If there is a mismatch in defaults (which there will be until 
FX switches the default, or after we which when running FX on an older 
JDK), then whichever toolkit loads first will use its default, and then 
the other one will pick up the already loaded library.

-- Kevin


Phil Race wrote:
> Bug: https://bugs.openjdk.java.net/browse/JDK-8198649
> Webrev: http://cr.openjdk.java.net/~prr/8198649/
>
> This is a very small change to switch the default GTK library loaded
> from GTK 2.2 to GTK 3.
>
> Both are supported as of JDK 9 but it still defaults to 2.2 and you use
> jdk.gtk.version=3 to switch.
>
> Since only one of these can be loaded a switch is necessary in case
> auto-detect fails or JDK get to load its version first, but making 
> GTK3 load
> by default will help with SWT interop as shown here  where we load
> Swing's GTK L+F followed by SWT
>
> ---
> import javax.swing.UIManager;
> import org.eclipse.swt.widgets.Display;
>
> public class SWT_Swing {
>  public static void main(String[] args) throws Exception {
> UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
>         Display display = new Display();
>  }
> }
>
> -- 
>
> /jdk9/bin/java -Djdk.gtk.verbose=true  -cp swt.jar:. SWT_Swing Looking 
> for GTK2 library...
> GTK2 library loaded.
>
> (java:21435): GLib-GObject-WARNING **: cannot register existing type 
> 'GdkDisplayManager'
>
> (java:21435): GLib-CRITICAL **: g_once_init_leave: assertion 'result 
> != 0' failed
>
> (java:21435): GLib-GObject-CRITICAL **: g_object_new: assertion 
> 'G_TYPE_IS_OBJECT (object_type)' failed
>
> ---
>
> As you can see SWT now cannot work since JDK loaded GTK 2.2 by default
> and unlike JDK SWT has no detection code or automatic fall back
>
> But with the proposed change we get no error :
> ~/jdk-11/build/linux-x86_64-normal-server-release/jdk/bin/java 
> -Djdk.gtk.verbose=true  -cp swt.jar:. SWT_Swing
> Looking for GTK3 library...
> GTK3 library loaded.
>
> Granted, the reverse problem would happen for apps that depend on GTK 2.2
> but that is looking backwards ..
>
> I have also run the SwingSet2 demo in the various cases and it is fine.
>
> We expect to make the same switch for JavaFX.
>
> -phil.
>
>
>