Theme Editor:

- use JetBrains Mono font for editor area
- added Inter font to allow using it in preview (Java 11+)

flatlaf-theme-editor/build.gradle.kts

@@ -22,6 +22,8 @@ plugins {
 dependencies {
 	implementation( project( ":flatlaf-core" ) )
 	implementation( project( ":flatlaf-extras" ) )
+	implementation( project( ":flatlaf-fonts-inter" ) )
+	implementation( project( ":flatlaf-fonts-jetbrains-mono" ) )
 
 	implementation( "com.miglayout:miglayout-swing:5.3" )
 	implementation( "com.fifesoft:rsyntaxtextarea:3.1.4" )
@@ -32,6 +34,8 @@ tasks {
 	jar {
 		dependsOn( ":flatlaf-core:jar" )
 		dependsOn( ":flatlaf-extras:jar" )
+		dependsOn( ":flatlaf-fonts-inter:jar" )
+		dependsOn( ":flatlaf-fonts-jetbrains-mono:jar" )
 
 		manifest {
 			attributes( "Main-Class" to "com.formdev.flatlaf.themeeditor.FlatLafThemeEditor" )

flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/themeeditor/FlatThemeEditorPane.java

@@ -34,6 +34,7 @@ import javax.swing.JPanel;
 import javax.swing.KeyStroke;
 import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
+import javax.swing.text.StyleContext;
 import org.fife.ui.autocomplete.AutoCompletion;
 import org.fife.ui.autocomplete.CompletionProvider;
 import org.fife.ui.rsyntaxtextarea.AbstractTokenMakerFactory;
@@ -48,6 +49,7 @@ import org.fife.ui.rtextarea.Gutter;
 import org.fife.ui.rtextarea.RTextArea;
 import org.fife.ui.rtextarea.RTextScrollPane;
 import org.fife.ui.rtextarea.SearchContext;
+import com.formdev.flatlaf.fonts.jetbrains_mono.FlatJetBrainsMonoFont;
 import com.formdev.flatlaf.util.UIScale;
 
 /**
@@ -128,8 +130,7 @@ class FlatThemeEditorPane
 	}
 
 	void updateTheme() {
-		Font defaultFont = RTextArea.getDefaultFont();
+		Font font = createEditorFont( 0 );
-		Font font = defaultFont.deriveFont( (float) UIManager.getFont( "defaultFont" ).getSize() );
 
 		textArea.setFont( font );
 		textArea.setBackground( UIManager.getColor( "FlatThemeEditorPane.background" ) );
@@ -161,14 +162,28 @@ class FlatThemeEditorPane
 	}
 
 	void updateFontSize( int sizeIncr ) {
-		Font defaultFont = RTextArea.getDefaultFont();
+		Font font = createEditorFont( sizeIncr );
-		Font font = defaultFont.deriveFont( (float) UIManager.getFont( "defaultFont" ).getSize() + sizeIncr );
 
 		textArea.setFont( font );
 		textArea.setSyntaxScheme( new FlatSyntaxScheme( font ) );
 		scrollPane.getGutter().setLineNumberFont( font );
 	}
 
+	private static Font createEditorFont( int sizeIncr ) {
+		int size = UIManager.getFont( "defaultFont" ).getSize() + sizeIncr;
+		StyleContext sc = StyleContext.getDefaultStyleContext();
+		Font font = sc.getFont( FlatJetBrainsMonoFont.FAMILY, Font.PLAIN, size );
+		if( isFallbackFont( font ) ) {
+			Font defaultFont = RTextArea.getDefaultFont();
+			font = defaultFont.deriveFont( (float) size );
+		}
+		return font;
+	}
+
+	private static boolean isFallbackFont( Font font ) {
+		return Font.DIALOG.equalsIgnoreCase( font.getFamily() );
+	}
+
 	void selected() {
 		if( findReplaceVisible )
 			showFindReplaceBar( false );

flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/themeeditor/FlatThemeFileEditor.java

@@ -63,6 +63,8 @@ import com.formdev.flatlaf.extras.FlatSVGIcon;
 import com.formdev.flatlaf.extras.FlatSVGUtils;
 import com.formdev.flatlaf.extras.FlatUIDefaultsInspector;
 import com.formdev.flatlaf.extras.components.*;
+import com.formdev.flatlaf.fonts.inter.FlatInterFont;
+import com.formdev.flatlaf.fonts.jetbrains_mono.FlatJetBrainsMonoFont;
 import com.formdev.flatlaf.icons.FlatClearIcon;
 import com.formdev.flatlaf.ui.FlatUIUtils;
 import com.formdev.flatlaf.util.StringUtils;
@@ -105,6 +107,10 @@ class FlatThemeFileEditor
 		System.setProperty( "user.language", "en" );
 
 		SwingUtilities.invokeLater( () -> {
+			if( SystemInfo.isJava_11_orLater )
+				FlatInterFont.install();
+			FlatJetBrainsMonoFont.install();
+
 			FlatLaf.registerCustomDefaultsSource( "com.formdev.flatlaf.themeeditor" );
 
 			try {