Added preferGtk3 to GTK loading. Fail loading GTK if GTK2 is forced, and

GTK2 cannot load. Code polish.

src/dorkbox/util/jna/linux/GtkEventDispatch.java

@@ -33,6 +33,7 @@ import dorkbox.util.Swt;
 public
 class GtkEventDispatch {
     static boolean FORCE_GTK2 = false;
+    static boolean PREFER_GTK3 = false;
     static boolean DEBUG = false;
 
     // have to save these in a field to prevent GC on the objects (since they go out-of-scope from java)
@@ -47,7 +48,7 @@ class GtkEventDispatch {
         }
     };
 
-    private static volatile boolean started = false;
+    private static boolean started = false;
 
     @SuppressWarnings("FieldCanBeLocal")
     private static Thread gtkUpdateThread = null;
@@ -60,14 +61,15 @@ class GtkEventDispatch {
 
 
 
-    public static
-    void startGui(final boolean FORCE_GTK2, final boolean DEBUG) {
+    public static synchronized
+    void startGui(final boolean forceGtk2, final boolean preferGkt3, final boolean debug) {
         // only permit one startup per JVM instance
         if (!started) {
             started = true;
 
-            GtkEventDispatch.FORCE_GTK2 = FORCE_GTK2;
-            GtkEventDispatch.DEBUG = DEBUG;
+            GtkEventDispatch.FORCE_GTK2 = forceGtk2;
+            GtkEventDispatch.PREFER_GTK3 = preferGkt3;
+            GtkEventDispatch.DEBUG = debug;
 
             // startup the GTK GUI event loop. There can be multiple/nested loops.
 
@@ -80,7 +82,7 @@ class GtkEventDispatch {
                     public
                     void run() {
                         Glib.GLogFunc orig = null;
-                        if (DEBUG) {
+                        if (debug) {
                             // don't suppress GTK warnings in debug mode
                             LoggerFactory.getLogger(GtkEventDispatch.class).debug("Running GTK Native Event Loop");
                         } else {
@@ -120,7 +122,7 @@ class GtkEventDispatch {
      * Waits for the all posted events to GTK to finish loading
      */
     @SuppressWarnings("Duplicates")
-    public static
+    public static synchronized
     void waitForEventsToComplete() {
         final CountDownLatch blockUntilStarted = new CountDownLatch(1);
 
@@ -275,22 +277,6 @@ class GtkEventDispatch {
         }
     }
 
-    public static
-    void shutdownGui() {
-        dispatchAndWait(new Runnable() {
-            @Override
-            public
-            void run() {
-                // If JavaFX/SWT is used, this is UNNECESSARY (and will break SWT/JavaFX shutdown)
-                if (!GtkLoader.alreadyRunningGTK) {
-                    Gtk2.gtk_main_quit();
-                }
-
-                started = false;
-            }
-        });
-    }
-
     public static
     void dispatchAndWait(final Runnable runnable) {
         if (isDispatch.get()) {
@@ -356,4 +342,20 @@ class GtkEventDispatch {
             isDispatch.set(false);
         }
     }
+    public static synchronized
+    void shutdownGui() {
+        dispatchAndWait(new Runnable() {
+            @Override
+            public
+            void run() {
+                // If JavaFX/SWT is used, this is UNNECESSARY (and will break SWT/JavaFX shutdown)
+                if (!GtkLoader.alreadyRunningGTK) {
+                    Gtk2.gtk_main_quit();
+                }
+
+                started = false;
+            }
+        });
+    }
+
 }

src/dorkbox/util/jna/linux/GtkLoader.java

@@ -62,7 +62,10 @@ class GtkLoader {
      * SWT uses GTK2 or GTK3. We do not work with the GTK3 version of SWT.
      */
     static {
-        boolean shouldUseGtk2 = GtkEventDispatch.FORCE_GTK2;
+        boolean forceGtk2 = GtkEventDispatch.FORCE_GTK2;
+        // prefer GTK3 and force GTK2 are mutually exclusive
+        boolean preferGtk3 = !forceGtk2 && GtkEventDispatch.PREFER_GTK3;
+
         boolean _isGtk2 = false;
         boolean _isLoaded = false;
         boolean _alreadyRunningGTK = false;
@@ -76,11 +79,6 @@ class GtkLoader {
         }
 
 
-        if (OSUtil.Linux.isKali()) {
-            // Kali linux has some WEIRD graphical oddities via GTK3. GTK2 looks just fine.
-            shouldUseGtk2 = true;
-        }
-
         // we can force the system to use the swing indicator, which WORKS, but doesn't support transparency in the icon. However, there
         // are certain GTK functions we might want to use (even if we are Swing or AWT), so we load GTK anyways...
 
@@ -88,7 +86,7 @@ class GtkLoader {
         String gtk2LibName = "gtk-x11-2.0";
         String gtk3LibName = "libgtk-3.so.0";
 
-        if (!_isLoaded && shouldUseGtk2) {
+        if (!_isLoaded && (forceGtk2 || !preferGtk3)) {
             try {
                 NativeLibrary library = JnaHelper.register(gtk2LibName, Gtk2.class);
 
@@ -113,6 +111,11 @@ class GtkLoader {
                     LoggerFactory.getLogger(GtkLoader.class).error("Error loading library", e);
                 }
             }
+
+            if (forceGtk2) {
+                // don't try anything else if we forced GTK2
+                _isLoaded = true;
+            }
         }
 
         // now for the defaults...