System File Chooser: Linux: show file dialog in dark if current FlatLaf theme is dark (PR #988)

with Java 8, some GLib related messages are logged to console and system file dialog is not shown
e.g.: `GLib-GObject-WARNING **: cannot register existing type 'GdkDisplayManager'`

with Java 17, the system file dialog is shown, but then JavaFX no longer works
with Java 21, the application quits/crashes immediately when trying to show system file dialog

also fixed Error Prone warning in `getFiltersForDialog()`

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeLinuxLibrary.java

@@ -37,7 +37,7 @@ import com.formdev.flatlaf.util.SystemInfo;
  */
 public class FlatNativeLinuxLibrary
 {
-	private static int API_VERSION_LINUX = 3002;
+	private static int API_VERSION_LINUX = 3003;
 
 	/**
 	 * Checks whether native library is loaded/available.
@@ -178,6 +178,7 @@ public class FlatNativeLinuxLibrary
 	 * to avoid blocking the AWT event dispatching thread.
 	 *
 	 * @param owner the owner of the file dialog; or {@code null}
+	 * @param dark preferred appearance of the file dialog: {@code 1} = prefer dark, {@code 0} = prefer light, {@code -1} = default
 	 * @param open if {@code true}, shows the open dialog; if {@code false}, shows the save dialog
 	 * @param title text displayed in dialog title; or {@code null}
 	 * @param okButtonLabel text displayed in default button; or {@code null}.
@@ -199,7 +200,7 @@ public class FlatNativeLinuxLibrary
 	 *
 	 * @since 3.7
 	 */
-	public native static String[] showFileChooser( Window owner, boolean open,
+	public native static String[] showFileChooser( Window owner, int dark, boolean open,
 		String title, String okButtonLabel, String currentName, String currentFolder,
 		int optionsSet, int optionsClear, FileChooserCallback callback,
 		int fileTypeIndex, String... fileTypes );

flatlaf-core/src/main/java/com/formdev/flatlaf/util/SystemFileChooser.java

@@ -22,9 +22,10 @@ import java.awt.SecondaryLoop;
 import java.awt.Toolkit;
 import java.awt.Window;
 import java.io.File;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
@@ -590,7 +591,7 @@ public class SystemFileChooser
 		if( filters.size() == 1 &&
 			filters.get( 0 ) == getAcceptAllFileFilter() &&
 			(fileFilter == getAcceptAllFileFilter() || fileFilter == null) )
-		  return Collections.emptyList();
+		  return new ArrayList<>();
 
 		// check whether current filter is already in list
 		if( (fileFilter != null && filters.contains( fileFilter )) || fileFilter == null )
@@ -1073,8 +1074,18 @@ public class SystemFileChooser
 	private static class LinuxFileChooserProvider
 		extends SystemFileChooserProvider
 	{
+		@Override
+		public File[] showDialog( Window owner, SystemFileChooser fc ) {
+			// fallback to Swing file chooser if JavaFX is initialized
+			if( isFXinitialized() )
+				return new SwingFileChooserProvider().showDialog( owner, fc );
+
+			return super.showDialog( owner, fc );
+		}
+
 		@Override
 		String[] showSystemDialog( Window owner, SystemFileChooser fc ) {
+			int dark = FlatLaf.isLafDark() ? 1 : 0;
 			boolean open = (fc.getDialogType() == OPEN_DIALOG);
 			String approveButtonText = fc.getApproveButtonText();
 			int approveButtonMnemonic = fc.getApproveButtonMnemonic();
@@ -1152,7 +1163,7 @@ public class SystemFileChooser
 				} : null;
 
 			// show system file dialog
-			return FlatNativeLinuxLibrary.showFileChooser( owner, open,
+			return FlatNativeLinuxLibrary.showFileChooser( owner, dark, open,
 				fc.getDialogTitle(), approveButtonText, currentName, currentFolder,
 				optionsSet, optionsClear, callback,
 				fileTypeIndex, fileTypes.toArray( new String[fileTypes.size()] ) );
@@ -1175,6 +1186,41 @@ public class SystemFileChooser
 			return buf.toString();
 		}
 
+
+		private static Boolean fxinitialized;
+
+		boolean isFXinitialized() {
+			if( fxinitialized != null )
+				return fxinitialized;
+
+			// check whether JavaFX is available
+			try {
+				Class.forName( "javafx.application.Platform", false, getClass().getClassLoader() );
+			} catch( ClassNotFoundException ex ) {
+				// JavaFX is not available
+				fxinitialized = false;
+				return fxinitialized;
+			}
+
+			// check whether JavaFX is initialized
+			try {
+				Class<?> cls = Class.forName( "javafx.application.Platform" );
+				Method m = cls.getMethod( "runLater", Runnable.class );
+				m.invoke( null, (Runnable) () -> {} );
+				fxinitialized = true;
+				return fxinitialized;
+			} catch( InvocationTargetException ex ) {
+				if( ex.getCause() instanceof IllegalStateException )
+					return false; // JavaFX is available, but not (yet) initialized
+			} catch( Throwable ex ) {
+				// ignore
+			}
+
+			// other error --> assume that JavaFX is not initialized
+			fxinitialized = false;
+			return fxinitialized;
+		}
+
 		//---- class LinuxApproveContext ----
 
 		private static class LinuxApproveContext

flatlaf-natives/flatlaf-natives-linux/src/main/cpp/ApiVersion.cpp

@@ -24,7 +24,7 @@
 
 // increase this version if changing API or functionality of native library
 // also update version in Java class com.formdev.flatlaf.ui.FlatNativeLinuxLibrary
-#define API_VERSION_LINUX		3002
+#define API_VERSION_LINUX		3003
 
 
 //---- JNI methods ------------------------------------------------------------

flatlaf-natives/flatlaf-natives-linux/src/main/cpp/GtkFileChooser.cpp

@@ -168,7 +168,7 @@ static void handle_response( GtkWidget* dialog, gint responseId, gpointer data )
 
 extern "C"
 JNIEXPORT jobjectArray JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_showFileChooser
-	( JNIEnv* env, jclass cls, jobject owner, jboolean open,
+	( JNIEnv* env, jclass cls, jobject owner, jint dark, jboolean open,
 		jstring title, jstring okButtonLabel, jstring currentName, jstring currentFolder,
 		jint optionsSet, jint optionsClear, jobject callback, jint fileTypeIndex, jobjectArray fileTypes )
 {
@@ -226,10 +226,40 @@ JNIEXPORT jobjectArray JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrar
 		gtk_window_set_modal( GTK_WINDOW( dialog ), true );
 
 		// file dialog should use same screen as owner
-		gtk_window_set_screen( GTK_WINDOW( dialog ), gdk_window_get_screen( gdkOwner ) );
+		GdkScreen* screen = gdk_window_get_screen( gdkOwner );
+		gtk_window_set_screen( GTK_WINDOW( dialog ), screen );
 
 		// set the transient when the file dialog is realized
 		g_signal_connect( dialog, "realize", G_CALLBACK( handle_realize ), gdkOwner );
+
+		// set light/dark appearance
+		if( dark >= 0 ) {
+			GtkSettings *settings = gtk_settings_get_for_screen( screen );
+
+			// get current GTK theme
+			gchar* currentGtkTheme;
+			g_object_get( settings, "gtk-theme-name", &currentGtkTheme, NULL );
+
+			const char* darkSuffix = "-dark";
+			bool isDarkGtkTheme = g_str_has_suffix( currentGtkTheme, darkSuffix );
+			if( isDarkGtkTheme && dark == 0 ) {
+				// current GTK theme is dark, but FlatLaf theme is light
+				// in this case, "gtk-application-prefer-dark-theme" does not work
+				// and there is no "gtk-application-prefer-light-theme" setting
+				// --> try to switch to light GTK theme (if available)
+				gchar* lightGtkTheme = g_strndup( currentGtkTheme, strlen( currentGtkTheme ) - strlen( darkSuffix ) );
+				gchar* themeDir = g_strdup_printf( "/usr/share/themes/%s", lightGtkTheme );
+				if( g_file_test( themeDir, G_FILE_TEST_IS_DIR ) )
+					g_object_set( settings, "gtk-theme-name", lightGtkTheme, NULL );
+				g_free( themeDir );
+				g_free( lightGtkTheme );
+			}
+
+			g_free( currentGtkTheme );
+
+			// let GTK know whether we prefer a dark theme
+			g_object_set( settings, "gtk-application-prefer-dark-theme", (dark == 1), NULL );
+		}
 	}
 
 	// show dialog

flatlaf-natives/flatlaf-natives-linux/src/main/headers/com_formdev_flatlaf_ui_FlatNativeLinuxLibrary.h

@@ -7,6 +7,22 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_TOPLEFT
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_TOPLEFT 0L
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_TOP
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_TOP 1L
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_TOPRIGHT
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_TOPRIGHT 2L
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_RIGHT
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_RIGHT 3L
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_BOTTOMRIGHT
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_BOTTOMRIGHT 4L
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_BOTTOM
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_BOTTOM 5L
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_BOTTOMLEFT
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_BOTTOMLEFT 6L
+#undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_LEFT
+#define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_SIZE_LEFT 7L
 #undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_MOVE
 #define com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_MOVE 8L
 #undef com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_FC_select_folder
@@ -48,10 +64,10 @@ JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_is
 /*
  * Class:     com_formdev_flatlaf_ui_FlatNativeLinuxLibrary
  * Method:    showFileChooser
- * Signature: (Ljava/awt/Window;ZLjava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;IILcom/formdev/flatlaf/ui/FlatNativeLinuxLibrary/FileChooserCallback;I[Ljava/lang/String;)[Ljava/lang/String;
+ * Signature: (Ljava/awt/Window;IZLjava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;IILcom/formdev/flatlaf/ui/FlatNativeLinuxLibrary/FileChooserCallback;I[Ljava/lang/String;)[Ljava/lang/String;
  */
 JNIEXPORT jobjectArray JNICALL Java_com_formdev_flatlaf_ui_FlatNativeLinuxLibrary_showFileChooser
-  (JNIEnv *, jclass, jobject, jboolean, jstring, jstring, jstring, jstring, jint, jint, jobject, jint, jobjectArray);
+  (JNIEnv *, jclass, jobject, jint, jboolean, jstring, jstring, jstring, jstring, jint, jint, jobject, jint, jobjectArray);
 
 /*
  * Class:     com_formdev_flatlaf_ui_FlatNativeLinuxLibrary

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatSystemFileChooserLinuxTest.java

@@ -24,6 +24,7 @@ import java.awt.Window;
 import java.util.Arrays;
 import java.util.concurrent.atomic.AtomicInteger;
 import javax.swing.*;
+import com.formdev.flatlaf.FlatLaf;
 import com.formdev.flatlaf.extras.components.*;
 import com.formdev.flatlaf.extras.components.FlatTriStateCheckBox.State;
 import com.formdev.flatlaf.testing.FlatSystemFileChooserTest.DummyModalDialog;
@@ -121,8 +122,9 @@ public class FlatSystemFileChooserLinuxTest
 
 		System.out.println( FlatNativeLinuxLibrary.isGtk3Available() );
 
+		int dark = FlatLaf.isLafDark() ? 1 : 0;
 		if( direct ) {
-			String[] files = FlatNativeLinuxLibrary.showFileChooser( owner, open,
+			String[] files = FlatNativeLinuxLibrary.showFileChooser( owner, dark, open,
 				title, okButtonLabel, currentName, currentFolder,
 				optionsSet.get(), optionsClear.get(), callback, fileTypeIndex, fileTypes );
 
@@ -132,7 +134,7 @@ public class FlatSystemFileChooserLinuxTest
 
 			String[] fileTypes2 = fileTypes;
 			new Thread( () -> {
-				String[] files = FlatNativeLinuxLibrary.showFileChooser( owner, open,
+				String[] files = FlatNativeLinuxLibrary.showFileChooser( owner, dark, open,
 					title, okButtonLabel, currentName, currentFolder,
 					optionsSet.get(), optionsClear.get(), callback, fileTypeIndex, fileTypes2 );
 

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatSystemFileChooserTest.java

@@ -77,7 +77,7 @@ public class FlatSystemFileChooserTest
 	FlatSystemFileChooserTest() {
 		initComponents();
 
-		if( !NativeJFileChooser.FX_AVAILABLE ) {
+		if( SystemInfo.isLinux || !NativeJFileChooser.FX_AVAILABLE ) {
 			javafxOpenButton.setEnabled( false );
 			javafxSaveButton.setEnabled( false );
 		}
@@ -231,7 +231,7 @@ public class FlatSystemFileChooserTest
 		int fileTypeIndex = fileTypeIndexSlider.getValue();
 		if( !useAcceptAllFileFilterCheckBox.isSelected() )
 			fc.setAcceptAllFileFilterUsed( false );
-		for( int i  = 0; i  < fileTypes.length; i += 2 ) {
+		for( int i = 0; i < fileTypes.length; i += 2 ) {
 			fc.addChoosableFileFilter( "*".equals( fileTypes[i+1] )
 				? fc.getAcceptAllFileFilter()
 				: new SystemFileChooser.FileNameExtensionFilter( fileTypes[i], fileTypes[i+1].split( ";" ) ) );
@@ -282,7 +282,7 @@ public class FlatSystemFileChooserTest
 		int fileTypeIndex = fileTypeIndexSlider.getValue();
 		if( !useAcceptAllFileFilterCheckBox.isSelected() )
 			fc.setAcceptAllFileFilterUsed( false );
-		for( int i  = 0; i  < fileTypes.length; i += 2 ) {
+		for( int i = 0; i < fileTypes.length; i += 2 ) {
 			fc.addChoosableFileFilter( "*".equals( fileTypes[i+1] )
 				? fc.getAcceptAllFileFilter()
 				: new FileNameExtensionFilter( fileTypes[i], fileTypes[i+1].split( ";" ) ) );