Modernize Swing UI with FlatLaf light theme and release 1.3.0

- Add FlatLaf 3.7.1 dependency and ModernLookAndFeel installer with rounded
  controls, slim scrollbars, and graceful fallback to the platform theme
- Install the theme before building the Swing UI in Main
- Widen the default window to 800x420 so all library actions stay visible
- Cover theme installation with a UI regression test
- Bump version to 1.3.0 and update the changelog

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SQLcadZ3v1J2pGcD8DbUdZ

Author: claude

CHANGELOG.md

@@ -2,6 +2,15 @@
 
 ## Unreleased
 
+## 1.3.0 - 2026-07-02
+### Added
+- FlatLaf 3.7.1 dependency and a `ModernLookAndFeel` installer with UI regression coverage.
+
+### Changed
+- Swing UI now starts with the modern FlatLaf light look and feel: flat controls, rounded buttons,
+  inputs, progress bars, and slim scrollbars instead of the legacy Metal theme.
+- Main window default size grew to 800x420 so all library actions stay visible with the new theme.
+
 ## 1.2.1 - 2026-06-19
 ### Changed
 - Hardened CI, release, Docker, and Scorecard workflows after repository audit.

pom.xml

@@ -7,7 +7,7 @@
 
   <groupId>com.krotname</groupId>
   <artifactId>javasoundrecorder</artifactId>
-  <version>1.2.1</version>
+  <version>1.3.0</version>
   <name>JavaSoundRecorder</name>
   <description>Microphone recorder with optional Dropbox upload.</description>
   <url>https://github.com/krotname/JavaSoundRecorder</url>
@@ -28,6 +28,7 @@
     <jacoco.version>0.8.15</jacoco.version>
     <slf4j.version>2.0.18</slf4j.version>
     <dropbox.version>8.0.0</dropbox.version>
+    <flatlaf.version>3.7.1</flatlaf.version>
     <jackson-core.version>2.22.0</jackson-core.version>
     <java-flac-encoder.version>0.3.8</java-flac-encoder.version>
     <junit.version>6.1.1</junit.version>
@@ -71,6 +72,11 @@
       <artifactId>java-flac-encoder</artifactId>
       <version>${java-flac-encoder.version}</version>
     </dependency>
+    <dependency>
+      <groupId>com.formdev</groupId>
+      <artifactId>flatlaf</artifactId>
+      <version>${flatlaf.version}</version>
+    </dependency>
 
     <dependency>
       <groupId>org.junit.jupiter</groupId>

src/main/java/com/krotname/javasoundrecorder/Main.java

@@ -18,6 +18,7 @@
 import com.krotname.javasoundrecorder.storage.DropboxUploadService;
 import com.krotname.javasoundrecorder.storage.NoopUploadService;
 import com.krotname.javasoundrecorder.storage.UploadService;
+import com.krotname.javasoundrecorder.ui.ModernLookAndFeel;
 import com.krotname.javasoundrecorder.ui.RecorderPanel;
 import com.krotname.javasoundrecorder.ui.RecorderSettings;
 import com.krotname.javasoundrecorder.ui.SettingsDialog;
@@ -118,6 +119,7 @@ private static void runCli(RecordingCoordinator coordinator) {
      * This avoids hidden background work after manual close in demonstration runs.
      */
     private static void launchUi(AppRuntime runtime) {
+        ModernLookAndFeel.install();
         // Keep Swing construction on the EDT and capture panel reference early to avoid
         // accidental nulls when wiring callbacks.
         EventQueue.invokeLater(() -> {

src/main/java/com/krotname/javasoundrecorder/ui/ModernLookAndFeel.java

@@ -0,0 +1,40 @@
+package com.krotname.javasoundrecorder.ui;
+
+import com.formdev.flatlaf.FlatLightLaf;
+import javax.swing.UIManager;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Installs the FlatLaf light look and feel so the Swing UI matches modern desktop applications.
+ * Keeps the platform default look and feel when installation fails so the UI stays usable.
+ */
+public final class ModernLookAndFeel {
+    private static final Logger logger = LoggerFactory.getLogger(ModernLookAndFeel.class);
+    private static final int CORNER_ARC = 12;
+    private static final int FOCUS_WIDTH = 1;
+    private static final int SCROLLBAR_WIDTH = 12;
+
+    private ModernLookAndFeel() {
+    }
+
+    /**
+     * Applies the modern light theme with rounded buttons, inputs, and progress bars.
+     *
+     * @return true when FlatLaf became the active look and feel
+     */
+    public static boolean install() {
+        UIManager.put("Component.arc", CORNER_ARC);
+        UIManager.put("Button.arc", CORNER_ARC);
+        UIManager.put("ProgressBar.arc", CORNER_ARC);
+        UIManager.put("TextComponent.arc", CORNER_ARC);
+        UIManager.put("Component.focusWidth", FOCUS_WIDTH);
+        UIManager.put("ScrollBar.thumbArc", CORNER_ARC);
+        UIManager.put("ScrollBar.width", SCROLLBAR_WIDTH);
+        if (FlatLightLaf.setup()) {
+            return true;
+        }
+        logger.warn("FlatLaf was not installed; keeping the platform default look and feel.");
+        return false;
+    }
+}

src/main/java/com/krotname/javasoundrecorder/ui/RecorderPanel.java

@@ -28,8 +28,8 @@
 public class RecorderPanel extends JPanel {
     private static final int VERTICAL_GAP = 10;
     private static final int HORIZONTAL_GAP = 10;
-    private static final int PREF_WIDTH = 620;
-    private static final int PREF_HEIGHT = 360;
+    private static final int PREF_WIDTH = 800;
+    private static final int PREF_HEIGHT = 420;
     private static final int BORDER_GAP = 12;
     private static final int DETAILS_ROWS = 4;
     private static final int PERCENT_MAX = 100;

src/test/java/com/krotname/javasoundrecorder/ui/ModernLookAndFeelUiTest.java

@@ -0,0 +1,23 @@
+package com.krotname.javasoundrecorder.ui;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.formdev.flatlaf.FlatLightLaf;
+import javax.swing.LookAndFeel;
+import javax.swing.UIManager;
+import org.junit.jupiter.api.Test;
+
+class ModernLookAndFeelUiTest {
+    @Test
+    void installsFlatLafLightThemeWithRoundedControls() throws Exception {
+        LookAndFeel previous = UIManager.getLookAndFeel();
+        try {
+            assertTrue(ModernLookAndFeel.install());
+            assertEquals(FlatLightLaf.class.getName(), UIManager.getLookAndFeel().getClass().getName());
+            assertEquals(12, UIManager.get("Button.arc"));
+        } finally {
+            UIManager.setLookAndFeel(previous);
+        }
+    }
+}