Theme Editor: increase/decrease editor font size

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

@@ -146,6 +146,15 @@ class FlatThemeEditorPane
 		errorStrip.setCaretMarkerColor( UIManager.getColor( "FlatThemeEditorPane.errorstrip.caretMarkerColor" ) );
 	}
 
+	void updateFontSize( int sizeIncr ) {
+		Font defaultFont = RTextArea.getDefaultFont();
+		Font font = defaultFont.deriveFont( (float) UIManager.getFont( "defaultFont" ).getSize() + sizeIncr );
+
+		textArea.setFont( font );
+		textArea.setSyntaxScheme( new FlatSyntaxScheme( font ) );
+		scrollPane.getGutter().setLineNumberFont( font );
+	}
+
 	@Override
 	public boolean requestFocusInWindow() {
 		return textArea.requestFocusInWindow();

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

@@ -62,6 +62,7 @@ public class FlatThemeFileEditor
 	private static final String KEY_RECENT_FILE = "recentFile";
 	private static final String KEY_WINDOW_BOUNDS = "windowBounds";
 	private static final String KEY_LAF = "laf";
+	private static final String KEY_FONT_SIZE_INCR = "fontSizeIncr";
 
 	private File dir;
 	private Preferences state;
@@ -374,6 +375,33 @@ public class FlatThemeFileEditor
 		}
 	}
 
+	private void incrFontSize() {
+		applyFontSizeIncr( getFontSizeIncr() + 1 );
+	}
+
+	private void decrFontSize() {
+		applyFontSizeIncr( getFontSizeIncr() - 1 );
+	}
+
+	private void resetFontSize() {
+		applyFontSizeIncr( 0 );
+	}
+
+	private void applyFontSizeIncr( int sizeIncr ) {
+		if( sizeIncr < -5 )
+			sizeIncr = -5;
+		if( sizeIncr == getFontSizeIncr() )
+			return;
+
+		for( FlatThemeEditorPane themeEditorPane : getThemeEditorPanes() )
+			themeEditorPane.updateFontSize( sizeIncr );
+		state.putInt( KEY_FONT_SIZE_INCR, sizeIncr );
+	}
+
+	private int getFontSizeIncr() {
+		return state.getInt( KEY_FONT_SIZE_INCR, 0 );
+	}
+
 	private void restoreState() {
 		state = Preferences.userRoot().node( PREFS_ROOT_PATH );
 
@@ -477,6 +505,9 @@ public class FlatThemeFileEditor
 		viewMenu = new JMenu();
 		lightLafMenuItem = new JRadioButtonMenuItem();
 		darkLafMenuItem = new JRadioButtonMenuItem();
+		incrFontSizeMenuItem = new JMenuItem();
+		decrFontSizeMenuItem = new JMenuItem();
+		resetFontSizeMenuItem = new JMenuItem();
 		windowMenu = new JMenu();
 		nextEditorMenuItem = new JMenuItem();
 		previousEditorMenuItem = new JMenuItem();
@@ -570,6 +601,25 @@ public class FlatThemeFileEditor
 				darkLafMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_F12, 0));
 				darkLafMenuItem.addActionListener(e -> darkLaf());
 				viewMenu.add(darkLafMenuItem);
+				viewMenu.addSeparator();
+
+				//---- incrFontSizeMenuItem ----
+				incrFontSizeMenuItem.setText("Increase Font Size");
+				incrFontSizeMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_PLUS, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
+				incrFontSizeMenuItem.addActionListener(e -> incrFontSize());
+				viewMenu.add(incrFontSizeMenuItem);
+
+				//---- decrFontSizeMenuItem ----
+				decrFontSizeMenuItem.setText("Decrease Font Size");
+				decrFontSizeMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_MINUS, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
+				decrFontSizeMenuItem.addActionListener(e -> decrFontSize());
+				viewMenu.add(decrFontSizeMenuItem);
+
+				//---- resetFontSizeMenuItem ----
+				resetFontSizeMenuItem.setText("Reset Font Size");
+				resetFontSizeMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_0, Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
+				resetFontSizeMenuItem.addActionListener(e -> resetFontSize());
+				viewMenu.add(resetFontSizeMenuItem);
 			}
 			menuBar.add(viewMenu);
 
@@ -650,6 +700,9 @@ public class FlatThemeFileEditor
 	private JMenu viewMenu;
 	private JRadioButtonMenuItem lightLafMenuItem;
 	private JRadioButtonMenuItem darkLafMenuItem;
+	private JMenuItem incrFontSizeMenuItem;
+	private JMenuItem decrFontSizeMenuItem;
+	private JMenuItem resetFontSizeMenuItem;
 	private JMenu windowMenu;
 	private JMenuItem nextEditorMenuItem;
 	private JMenuItem previousEditorMenuItem;

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

@@ -116,6 +116,27 @@ new FormModel {
 						"accelerator": static javax.swing.KeyStroke getKeyStroke( 123, 0, false )
 						addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "darkLaf", false ) )
 					} )
+					add( new FormComponent( "javax.swing.JPopupMenu$Separator" ) {
+						name: "separator2"
+					} )
+					add( new FormComponent( "javax.swing.JMenuItem" ) {
+						name: "incrFontSizeMenuItem"
+						"text": "Increase Font Size"
+						"accelerator": static javax.swing.KeyStroke getKeyStroke( 521, 4226, false )
+						addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "incrFontSize", false ) )
+					} )
+					add( new FormComponent( "javax.swing.JMenuItem" ) {
+						name: "decrFontSizeMenuItem"
+						"text": "Decrease Font Size"
+						"accelerator": static javax.swing.KeyStroke getKeyStroke( 45, 4226, false )
+						addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "decrFontSize", false ) )
+					} )
+					add( new FormComponent( "javax.swing.JMenuItem" ) {
+						name: "resetFontSizeMenuItem"
+						"text": "Reset Font Size"
+						"accelerator": static javax.swing.KeyStroke getKeyStroke( 48, 4226, false )
+						addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "resetFontSize", false ) )
+					} )
 				} )
 				add( new FormContainer( "javax.swing.JMenu", new FormLayoutManager( class javax.swing.JMenu ) ) {
 					name: "windowMenu"