FlatLaf look-and-feel with better Dark mode support. (#23)

This PR configures Symon to use the FlatLaf Swing look-and-feel, giving both a slightly more modern look but also much better support for Dark/Light UI modes. Additional small tweaks to make the UI more readable in both Dark/Light modes.

Detection of system theme also added, selecting the Dark/Light FlatLaf variant accordingly.

Gets rid of need for the hardcoded Metal UI for text fields in StatusPanel workaround as well, as FlatLaf renders these small fields correctly.

Reviewed-on: https://codeberg.org/sethm/symon/pulls/23
Reviewed-by: Seth Morabito <sethm@noreply.codeberg.org>

pom.xml

@@ -1,5 +1,6 @@
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/maven-v4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/maven-v4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.loomcom.symon</groupId>
     <artifactId>symon</artifactId>
@@ -15,12 +16,33 @@
             UTF-8
         </project.reporting.outputEncoding>
     </properties>
+    <repositories>
+        <repository>
+            <id>jitpack.io</id>
+            <url>https://jitpack.io</url>
+        </repository>
+    </repositories>
     <dependencies>
         <dependency>
             <groupId>ch.qos.logback</groupId>
             <artifactId>logback-classic</artifactId>
             <version>1.5.16</version>
         </dependency>
+        <dependency>
+            <groupId>commons-cli</groupId>
+            <artifactId>commons-cli</artifactId>
+            <version>1.5.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.formdev</groupId>
+            <artifactId>flatlaf</artifactId>
+            <version>3.7.1</version>
+        </dependency>
+        <dependency>
+            <groupId>com.github.Dansoftowner</groupId>
+            <artifactId>jSystemThemeDetector</artifactId>
+            <version>3.9.1</version>
+        </dependency>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
@@ -33,11 +55,6 @@
             <version>4.11.0</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>commons-cli</groupId>
-            <artifactId>commons-cli</artifactId>
-            <version>1.5.0</version>
-        </dependency>
     </dependencies>
 
     <build>
@@ -48,7 +65,8 @@
                 <version>3.2.0</version>
                 <configuration>
                     <transformers>
-                        <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                        <transformer
+                            implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                             <mainClass>com.loomcom.symon.Main</mainClass>
                         </transformer>
                     </transformers>

src/main/java/com/loomcom/symon/Main.java

@@ -25,14 +25,15 @@
 package com.loomcom.symon;
 
 import com.loomcom.symon.machines.*;
+import com.loomcom.symon.ui.Ui;
+
 import org.apache.commons.cli.*;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.util.Locale;
-import javax.swing.JOptionPane;
+
 import javax.swing.SwingUtilities;
-import javax.swing.UIManager;
 
 public class Main {
     private final static Logger logger = LoggerFactory.getLogger(Main.class.getName());
@@ -58,6 +59,7 @@ public class Main {
         CommandLineParser parser = new DefaultParser();
 
         try {
+
             CommandLine line = parser.parse(options, args);
             InstructionTable.CpuBehavior cpuBehavior = null;
             String romFile = null;
@@ -116,27 +118,11 @@ public class Main {
                 haltOnBreak = true;
             }
 
+            Ui.initUi();
+
             while (true) {
                 if (machineClass == null) {
-                    Object[] possibilities = { "Symon", "Multicomp", "Simple", "BenEater" };
-                    String s = (String) JOptionPane.showInputDialog(
-                            null,
-                            "Please choose the machine type to be emulated:",
-                            "Machine selection",
-                            JOptionPane.PLAIN_MESSAGE,
-                            null,
-                            possibilities,
-                            "Symon");
-
-                    if (s != null && s.equals("Multicomp")) {
-                        machineClass = MulticompMachine.class;
-                    } else if (s != null && s.equals("Simple")) {
-                        machineClass = SimpleMachine.class;
-                    } else if (s != null && s.equals("BenEater")) {
-                        machineClass = BenEaterMachine.class;
-                    } else {
-                        machineClass = SymonMachine.class;
-                    }
+                    machineClass = Ui.showMachineSelectionDialog();
                 }
 
                 if (cpuBehavior == null) {
@@ -146,9 +132,8 @@ public class Main {
                 final Simulator simulator = new Simulator(machineClass, cpuBehavior, romFile, haltOnBreak);
 
                 SwingUtilities.invokeLater(() -> {
+                    // Create the main UI window:
                     try {
-                        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-                        // Create the main UI window
                         simulator.createAndShowUi();
                     } catch (Exception e) {
                         logger.error("Error during Symon UI initialization: {}", e.getMessage());
@@ -168,4 +153,5 @@ public class Main {
             logger.error("Could not start Symon. Reason: {}", ex.getMessage());
         }
     }
+
 }

src/main/java/com/loomcom/symon/ui/BreakpointsWindow.java

@@ -70,7 +70,6 @@ public class BreakpointsWindow extends JFrame {
 
         final JTable breakpointsTable = new JTable(breakpoints);
         breakpointsTable.setShowGrid(true);
-        breakpointsTable.setGridColor(Color.LIGHT_GRAY);
         breakpointsTable.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
         breakpointsTable.getSelectionModel().addListSelectionListener(e -> removeButton.setEnabled(e.getFirstIndex() > -1));
 

src/main/java/com/loomcom/symon/ui/StatusPanel.java

@@ -86,7 +86,7 @@ public class StatusPanel extends JPanel {
 
     private void createUi() {
         Border emptyBorder = BorderFactory.createEmptyBorder(EMPTY_BORDER, EMPTY_BORDER,
-                                                             EMPTY_BORDER, EMPTY_BORDER);
+                EMPTY_BORDER, EMPTY_BORDER);
         Border etchedBorder = BorderFactory.createEtchedBorder(EtchedBorder.LOWERED);
 
         setBorder(BorderFactory.createCompoundBorder(emptyBorder, etchedBorder));
@@ -125,16 +125,15 @@ public class StatusPanel extends JPanel {
 
         // Add tool-tip text
         carryFlagLabel.setToolTipText("Carry: The last operation caused an overflow " +
-                                      "from bit 7 of the result or an underflow from bit 0");
+                "from bit 7 of the result or an underflow from bit 0");
         zeroFlagLabel.setToolTipText("Zero: The result of the last operation was 0");
         irqDisableFlagLabel.setToolTipText("Interrupt Disable: Processor will not respond to IRQ");
         decimalModeFlagLabel.setToolTipText("Decimal Mode");
         breakFlagLabel.setToolTipText("Break: BRK instruction occurred");
         overflowFlagLabel.setToolTipText("Overflow: The result of the last operation was " +
-                                         "an invalid 2's complement result");
+                "an invalid 2's complement result");
         negativeFlagLabel.setToolTipText("Negative: The result of the last operation set bit 7");
 
-
         statusFlagsPanel.add(negativeFlagLabel);
         statusFlagsPanel.add(overflowFlagLabel);
         statusFlagsPanel.add(breakFlagLabel);
@@ -243,7 +242,6 @@ public class StatusPanel extends JPanel {
         constraints.gridy = 1;
         add(statusFlagsPanel, constraints);
 
-
         constraints.insets = new Insets(5, 0, 0, 0);
         constraints.gridy = 2;
         add(opcodeLabel, constraints);
@@ -392,13 +390,6 @@ public class StatusPanel extends JPanel {
         textField.setMinimumSize(size);
         textField.setMaximumSize(size);
         textField.setPreferredSize(size);
-        textField.setBackground(Color.WHITE);
-        // Although we usually defer to the system look-and-feel, for
-        // these small text fields in particular, we use a Metal
-        // look-and-feel because native look-and-feel breaks very small
-        // text fields under GTK+ (they are drawn with an inner margin
-        // even if the margin is set to 0)
-        textField.setUI(new MetalTextFieldUI());
 
         return textField;
     }

src/main/java/com/loomcom/symon/ui/Ui.java

@@ -0,0 +1,124 @@
+/*
+ * Copyright (c) 2008-2025 Seth J. Morabito <web@loomcom.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package com.loomcom.symon.ui;
+
+import javax.swing.JDialog;
+import javax.swing.JFrame;
+import javax.swing.JOptionPane;
+import javax.swing.LookAndFeel;
+import javax.swing.UIManager;
+import javax.swing.UnsupportedLookAndFeelException;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.formdev.flatlaf.FlatDarkLaf;
+import com.formdev.flatlaf.FlatLaf;
+import com.formdev.flatlaf.FlatLightLaf;
+import com.formdev.flatlaf.util.SystemInfo;
+import com.jthemedetecor.OsThemeDetector;
+import com.loomcom.symon.machines.BenEaterMachine;
+import com.loomcom.symon.machines.MulticompMachine;
+import com.loomcom.symon.machines.SimpleMachine;
+import com.loomcom.symon.machines.SymonMachine;
+
+public final class Ui {
+    private final static Logger logger = LoggerFactory.getLogger(Ui.class.getName());
+
+    public static void initUi() throws UnsupportedLookAndFeelException {
+        // Location of properties resources for app-specific UI defaults:
+        FlatLaf.registerCustomDefaultsSource("com.loomcom.symon.themes");
+
+        // Enable automatic scaling, based on system DPI settings:
+        System.setProperty("sun.java2d.uiScale.enabled", "true");
+        System.setProperty("sun.java2d.uiScale", "1x");
+        System.setProperty("flatlaf.uiScale", "1x");
+
+        // OS-specific tweaking:
+
+        if (SystemInfo.isLinux) {
+            logger.debug("Adapting UI for Linux.");
+
+            // Enable custom window decorations:
+            JFrame.setDefaultLookAndFeelDecorated(true);
+            JDialog.setDefaultLookAndFeelDecorated(true);
+        }
+
+        else if (SystemInfo.isMacOS) {
+            logger.debug("Adapting UI for MacOS.");
+
+            // Move menu bar from JFrame window to top of screen:
+            System.setProperty("apple.laf.useScreenMenuBar", "true");
+            // Set name used in screen menu bar (first menu after Apple menu):
+            System.setProperty("apple.awt.application.name", "Symon");
+            // Use current macOS appearance (light/dark) for window title bars:
+            System.setProperty("apple.awt.application.appearance", "system");
+        }
+
+        else if (SystemInfo.isWindows) {
+            logger.debug("Adapting UI for Windows.");
+        }
+
+        UIManager.setLookAndFeel(createLookAndFeel());
+    }
+
+    public static Class<?> showMachineSelectionDialog() {
+        Object[] possibilities = { "Symon", "Multicomp", "Simple", "BenEater" };
+        String s = (String) JOptionPane.showInputDialog(
+                null,
+                "Please choose the machine type to be emulated:",
+                "Machine selection",
+                JOptionPane.PLAIN_MESSAGE,
+                null,
+                possibilities,
+                "Symon");
+
+        if (s != null && s.equals("Multicomp")) {
+            return MulticompMachine.class;
+        } else if (s != null && s.equals("Simple")) {
+            return SimpleMachine.class;
+        } else if (s != null && s.equals("BenEater")) {
+            return BenEaterMachine.class;
+        } else {
+            return SymonMachine.class;
+        }
+    }
+
+    private static LookAndFeel createLookAndFeel() {
+        final OsThemeDetector themeDetector = OsThemeDetector.getDetector();
+        final boolean systemThemeIsDark = themeDetector.isDark();
+
+        // Set light/dark mode depending on what can be detected from the system theme:
+        FlatLaf theme;
+        if (systemThemeIsDark) {
+            logger.debug("Using DARK theme.");
+            theme = new FlatDarkLaf();
+        } else {
+            logger.debug("Using LIGHT theme.");
+            theme = new FlatLightLaf();
+        }
+        return theme;
+    }
+
+}

src/main/resources/com.loomcom.symon.themes/FlatDarkLaf.properties

@@ -0,0 +1,3 @@
+# Loaded for FlatDarkLaf theme only.
+
+Colors.accent.default = #4B6EAF

src/main/resources/com.loomcom.symon.themes/FlatLaf.properties

@@ -0,0 +1 @@
+# Loaded for all FlatLaf themes.

src/main/resources/com.loomcom.symon.themes/FlatLightLaf.properties

@@ -0,0 +1,3 @@
+# Loaded for FlatLightLaf theme only.
+
+Colors.accent.default = #2675BF