Fix scaling issues on some windows

Only PA and PB implemented, not tested

.gitea/workflows/build.yaml

@@ -0,0 +1,36 @@
+name: Build and Test
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    container:
+      image: catthehacker/ubuntu:act-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup JDK
+        uses: actions/setup-java@v6
+        with:
+          distribution: temurin
+          java-version: '21'
+          #cache: maven
+
+      - name: Install Maven
+        run: apt-get update && apt-get install -y maven
+
+      - name: Test and package
+        run: mvn -B verify
+
+      - name: Upload jar
+        uses: actions/upload-artifact@v3
+        with:
+          name: package
+          path: target/*.jar

.gitea/workflows/release.yaml

@@ -0,0 +1,33 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    container:
+      image: catthehacker/ubuntu:act-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup JDK
+        uses: actions/setup-java@v6
+        with:
+          distribution: temurin
+          java-version: '21'
+
+      - name: Install Maven
+        run: apt-get update && apt-get install -y maven
+
+      - name: Package
+        run: mvn -B verify
+
+      - name: Create release
+        uses: https://gitea.com/actions/gitea-release-action@v1
+        with:
+          files: |-
+            target/symon*.jar

README.md

@@ -1,13 +1,13 @@
-SYMON - A 6502 System Simulator
+kSYMON - A 6502 System Simulator
 ===============================
 
-**Version:** 1.5.0
+**Version:** 1.5.1.1k
 
-**Last Updated:** 30 March, 2025
+**Last Updated:** 24 September, 2026
 
 See the file COPYING for license.
 
-![Symon Simulator in Action](https://github.com/sethm/symon/raw/master/screenshots/full.jpg)
+![Symon Simulator in Action](https://codeberg.org/sethm/symon/raw/master/screenshots/full.jpg)
 
 ## 1.0 About
 
@@ -71,9 +71,16 @@ memory.
   - `$6000`--`$600F`: 6522 VIA
   - `$8000`--`$FFFF`: 16KB ROM
 
+#### 3.1.5 Mike42 Memory Map
+
+  - `$0000`--`$7FFF`: 32KB RAM
+  - `$8000`--`$800F`: 6522 VIA
+  - `$8400`--`$8403`: MOS 6551 ACIA (Serial Console)
+  - `$C000`--`$FFFF`: 16KB ROM
+
 ### 3.2 Serial Console and CPU Status
 
-![Serial Console](https://github.com/sethm/symon/raw/master/screenshots/console.png)
+![Serial Console](https://codeberg.org/sethm/symon/raw/master/screenshots/console.png)
 
 The main window of the simulator acts as the primary Input/Output
 system through a virtual serial terminal. It also provides CPU status.
@@ -100,13 +107,13 @@ see the official datasheet:
 
   - [MOS 6551 ACIA](http://archive.6502.org/datasheets/mos_6551_acia.pdf)
 
-![Font Selection](https://github.com/sethm/symon/raw/master/screenshots/font_selection.png)
+![Font Selection](https://codeberg.org/sethm/symon/raw/master/screenshots/font_selection.png)
 
 The console supports font sizes from 10 to 20 points.
 
 ### 3.3 ROM Loading
 
-![ROM Loading](https://github.com/sethm/symon/raw/master/screenshots/load_rom.png)
+![ROM Loading](https://codeberg.org/sethm/symon/raw/master/screenshots/load_rom.png)
 
 Symon can load any appropriately sized ROM image. The Symon
 architecture expects as 16KB (16384 byte) ROM image, while the
@@ -117,32 +124,32 @@ address.
 
 ### 3.4 Memory Window
 
-![Memory Window](https://github.com/sethm/symon/raw/master/screenshots/memory_window.png)
+![Memory Window](https://codeberg.org/sethm/symon/raw/master/screenshots/memory_window.png)
 
 Memory contents can be viewed (and edited) one page at a time through the Memory Window.
 
 ### 3.5 Trace Log
 
-![Trace Log](https://github.com/sethm/symon/raw/master/screenshots/trace_log.png)
+![Trace Log](https://codeberg.org/sethm/symon/raw/master/screenshots/trace_log.png)
 
 The last 20,000 execution steps are disassembled and logged to the Trace Log
 Window.
 
 ### 3.6 Simulator Speeds
 
-![Speeds](https://github.com/sethm/symon/raw/master/screenshots/simulator_menu.png)
+![Speeds](https://codeberg.org/sethm/symon/raw/master/screenshots/simulator_menu.png)
 
 Simulated speeds may be set from 1MHz to 8MHz.
 
 ### 3.7 Breakpoints
 
-![Breakpoints](https://github.com/sethm/symon/raw/master/screenshots/breakpoints.png)
+![Breakpoints](https://codeberg.org/sethm/symon/raw/master/screenshots/breakpoints.png)
 
 Breakpoints can be set and removed through the Breakpoints window.
 
 ### 3.8 Experimental 6545 CRTC Video
 
-![Composite Video](https://github.com/sethm/symon/raw/master/screenshots/video_window.png)
+![Composite Video](https://codeberg.org/sethm/symon/raw/master/screenshots/video_window.png)
 
 This feature is highly experimental. It's possible to open a video window
 from the "View" menu.  This window simulates the output of a MOS 6545 CRT
@@ -229,7 +236,18 @@ to specify machine type and CPU type. The options are:
   - `-r`,`-rom <file>`: Use the specified file as the ROM image.
   - `-b`,`-brk`: Halt the simulator on a BRK instruction (default is to continue)
 
-### 4.2 ROM images
+### 4.2 High-DPI UI scaling
+
+In certain environments with high-DPI (e.g. 4K) displays, the UI may
+not automatically scale and appear quite tiny. This can be fixed
+with the command line argument `-Dsun.java2d.uiScale=<factor>`,
+for example:
+
+```
+java -Dsun.java2d.uiScale=2.0 -jar symon-1.5.0.jar
+```
+
+### 4.3 ROM images
 
 The simulator requires a ROM image loaded into memory to work
 properly. Without a ROM in memory, the simulator will not be able to
@@ -247,7 +265,7 @@ architecture named 'ehbasic.rom', containing Lee Davison's Enhanced
 *Note*: Presently, EhBASIC only works with the Symon machine
  architecture, not with MULTICOMP.
 
-### 4.3 Loading A Program
+### 4.4 Loading A Program
 
 In addition to ROM images, programs in the form of raw binary object files can
 be loaded directly into memory from "Load Program..." in the File menu.
@@ -263,7 +281,7 @@ for testing.
 
 - 'hello.prg' will continuously print "Hello, 6502 World!" to the console.
 
-### 4.4 Running
+### 4.5 Running
 
 After loading a program or ROM image, clicking "Run" will start the simulator
 running.

pom.xml

@@ -1,10 +1,11 @@
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+<project xmlns="https://maven.apache.org/POM/4.0.0"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/maven-v4.0.0.xsd">
+    xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="https://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>
     <packaging>jar</packaging>
-    <version>1.5.0</version>
+    <version>1.5.1.1k</version>
     <name>symon</name>
     <url>https://git.loomcom.com/seth/symon</url>
     <properties>
@@ -15,11 +16,32 @@
             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>
+            <version>1.5.34</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>
@@ -34,9 +56,9 @@
             <scope>test</scope>
         </dependency>
         <dependency>
-            <groupId>commons-cli</groupId>
+            <groupId>net.java.dev.jna</groupId>
-            <artifactId>commons-cli</artifactId>
+            <artifactId>jna</artifactId>
-            <version>1.5.0</version>
+            <version>5.14.0</version>
         </dependency>
     </dependencies>
 
@@ -48,7 +70,8 @@
                 <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>
@@ -79,8 +102,8 @@
                 <version>3.7.0</version>
                 <configuration>
                     <compilerArgument>-Xlint:unchecked</compilerArgument>
-                    <source>11</source>
+                    <source>16</source>
-                    <target>11</target>
+                    <target>16</target>
                 </configuration>
             </plugin>
 
@@ -120,4 +143,4 @@
             </plugin>
         </plugins>
     </build>
-</project>
+</project>

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

@@ -25,19 +25,20 @@
 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());
 
-     /**
+    /**
      * Main entry point to the simulator. Creates a simulator and shows the main
      * window.
      *
@@ -49,6 +50,7 @@ public class Main {
 
         Options options = new Options();
 
+        options.addOption(new Option("h", "help", false, "Print this message."));
         options.addOption(new Option("m", "machine", true, "Specify machine type."));
         options.addOption(new Option("c", "cpu", true, "Specify CPU type."));
         options.addOption(new Option("r", "rom", true, "Specify ROM file."));
@@ -57,11 +59,18 @@ public class Main {
         CommandLineParser parser = new DefaultParser();
 
         try {
+
             CommandLine line = parser.parse(options, args);
             InstructionTable.CpuBehavior cpuBehavior = null;
             String romFile = null;
             boolean haltOnBreak = false;
 
+            if (line.hasOption("help")) {
+                HelpFormatter formatter = new HelpFormatter();
+                formatter.printHelp("symon", options, false);
+                return;
+            }
+
             if (line.hasOption("machine")) {
                 String machine = line.getOptionValue("machine").toLowerCase(Locale.ENGLISH);
                 switch (machine) {
@@ -77,6 +86,9 @@ public class Main {
                     case "beneater":
                         machineClass = BenEaterMachine.class;
                         break;
+                    case "mike42":
+                        machineClass = MichaelBillingtonMachine.class;
+                        break;
                     default:
                         logger.error("Could not start Symon. Unknown machine type {}", machine);
                         return;
@@ -109,28 +121,11 @@ public class Main {
                 haltOnBreak = true;
             }
 
+            Ui.initUi();
+
             while (true) {
                 if (machineClass == null) {
-                    Object[] possibilities = {"Symon", "Multicomp", "Simple", "BenEater"};
+                    machineClass = Ui.showMachineSelectionDialog();
-                    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;
-                    }
                 }
 
                 if (cpuBehavior == null) {
@@ -140,9 +135,8 @@ 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());
@@ -150,7 +144,6 @@ public class Main {
                     }
                 });
 
-
                 Simulator.MainCommand cmd = simulator.waitForCommand();
 
                 if (cmd.equals(Simulator.MainCommand.SELECTMACHINE)) {
@@ -163,4 +156,5 @@ public class Main {
             logger.error("Could not start Symon. Reason: {}", ex.getMessage());
         }
     }
+
 }

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

@@ -23,6 +23,7 @@
 
 package com.loomcom.symon;
 
+import com.formdev.flatlaf.util.UIScale;
 import com.loomcom.symon.devices.Memory;
 import com.loomcom.symon.exceptions.*;
 import com.loomcom.symon.machines.Machine;
@@ -53,7 +54,7 @@ public class Simulator {
 
     // UI constants
     private static final int DEFAULT_FONT_SIZE = 12;
-    private static final Font DEFAULT_FONT = new Font(Font.MONOSPACED, Font.PLAIN, DEFAULT_FONT_SIZE);
+    private static final Font DEFAULT_FONT = new Font(Font.MONOSPACED, Font.PLAIN, UIScale.scale(DEFAULT_FONT_SIZE));
     private static final int CONSOLE_BORDER_WIDTH = 10;
 
     // Clock periods, in NS, for each speed. 0MHz, 1MHz, 2MHz, 3MHz, 4MHz, 5MHz, 6MHz, 7MHz, 8MHz.

src/main/java/com/loomcom/symon/devices/Via6522.java

@@ -25,6 +25,7 @@ package com.loomcom.symon.devices;
 
 import com.loomcom.symon.exceptions.MemoryAccessException;
 import com.loomcom.symon.exceptions.MemoryRangeException;
+import com.loomcom.symon.util.Utils;
 
 /**
  * Skeleton for future implementation of a MOS 6522 VIA.
@@ -32,18 +33,82 @@ import com.loomcom.symon.exceptions.MemoryRangeException;
 public class Via6522 extends Pia {
     public static final int VIA_SIZE = 16;
 
+
+    static final int IOB_REG    = 0;    // Output Register B / Input Register B
+    static final int IOA_REG    = 1;    // Output Register A / Input Register A
+    static final int DDRB_REG   = 2;    // Data Direction Register B
+    static final int DDRA_REG   = 3;    // Data Direction Register A
+    static final int T1CL_REG   = 4;    // T1 Low-Order Counter / Latches
+    static final int T1CH_REG   = 5;    // T1 High-Order Counter
+    static final int T1LL_REG   = 6;    // T1 Low-Order Latches
+    static final int T1LH_REG   = 7;    // T1 High-Order Latches
+    static final int T2CL_REG   = 8;    // T2 Low-Order Counter / Latches
+    static final int T2CH_REG   = 9;    // T2 High-Order Counter
+    static final int SR_REG     = 10;   // Shift Register
+    static final int AuxC_REG   = 11;   // Auxiliary Control Register
+    static final int PerC_REG   = 12;   // Peripheral Control Register
+    static final int IntF_REG   = 13;   // Interrupt Flag Register
+    static final int IntE_REG   = 14;   // Interrupt Enable Register
+    static final int IOANH_REG  = 15;   // Same as Register 1 (IOA), but no Handshake
+
+    private int outputRegisterB, inputRegisterB;
+    private int outputRegisterA, inputRegisterA;
+    private int dataDirectionB,  dataDirectionA;
+
     public Via6522(int address) throws MemoryRangeException {
         super(address, address + VIA_SIZE - 1, "MOS 6522 VIA");
+        outputRegisterA = outputRegisterB = 0;
+        dataDirectionA = dataDirectionB = 0;
     }
 
     @Override
     public void write(int address, int data) throws MemoryAccessException {
-        // TODO: Implement write.
+        switch (address) {
+            case IOB_REG    -> outputRegisterB  = data & 0xFF;
+            case IOA_REG    -> outputRegisterA  = data & 0xFF;
+            case DDRB_REG   -> dataDirectionB   = data & 0xFF;
+            case DDRA_REG   -> dataDirectionA   = data & 0xFF;
+            case IOANH_REG  -> outputRegisterA  = data & 0xFF;
+            default -> throw new MemoryAccessException("No Register or Not Implemented!");
+        }
     }
 
     @Override
     public int read(int address, boolean cpuAccess) throws MemoryAccessException {
-        // TODO: Implement read.
+        return switch (address) {
-        return 0;
+            case IOB_REG    -> pbRead();
+            case IOA_REG    -> paRead();
+            case DDRB_REG   -> dataDirectionB;
+            case DDRA_REG   -> dataDirectionA;
+            case IOANH_REG  -> paRead();
+            default -> throw new MemoryAccessException("No Register or Not Implemented!");
+        };
+    }
+
+    public void setInputRegisterB(int data) {
+        inputRegisterB = data & 0xFF;
+    }
+
+    public void setInputRegisterA(int data) {
+        inputRegisterA = data & 0xFF;
+    }
+
+
+    public String getPBStatus() {
+        return "%" + Utils.byteToBin(pbRead());
+    }
+
+    public String getPAStatus() {
+        return "%" + Utils.byteToBin(paRead());
+    }
+
+    private int pbRead() {
+        // Return bits of output register where DDRB is 1 and input register where DDRB is 0
+        return (outputRegisterB & dataDirectionB) | (inputRegisterB & ~dataDirectionB);
+    }
+
+    private int paRead() {
+        // Return bits of output register where DDRB is 1 and input register where DDRB is 0
+        return (outputRegisterA & dataDirectionA) | (inputRegisterA & ~dataDirectionA);
     }
 }

src/main/java/com/loomcom/symon/machines/MichaelBillingtonMachine.java

@@ -0,0 +1,133 @@
+package com.loomcom.symon.machines;
+
+import com.loomcom.symon.Bus;
+import com.loomcom.symon.Cpu;
+import com.loomcom.symon.devices.*;
+import com.loomcom.symon.exceptions.MemoryRangeException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.File;
+
+public class MichaelBillingtonMachine implements Machine{
+
+    private static final Logger logger = LoggerFactory.getLogger(MichaelBillingtonMachine.class.getName());
+
+    // Constants used by the simulated system
+    private static final int BUS_BOTTOM = 0x0000;
+    private static final int BUS_TOP    = 0xffff;
+
+    // 32k of ram, from $0000 to $7fff
+    private static final int MEMORY_BASE = 0x0000;
+    private static final int MEMORY_SIZE = 0x8000;
+
+    // VIA at $8000-$800f
+    private static final int PIA_BASE = 0x8000;
+
+    // ACIA at $8400-$8403
+    private static final int ACIA_BASE = 0x8400;
+
+    // 16k ROM from $c000 to $ffff
+    private static final int ROM_BASE = 0xc000;
+    private static final int ROM_SIZE = 0x4000;
+
+    private final   Bus     bus;
+    private final   Cpu     cpu;
+    private final   Acia    acia;
+    private final   Pia     pia;
+    private final   Memory  ram;
+    private         Memory  rom;
+
+    public MichaelBillingtonMachine(String romFile) throws Exception {
+        this.bus = new Bus(BUS_BOTTOM, BUS_TOP);
+        this.cpu = new Cpu();
+        this.ram = new Memory(MEMORY_BASE, MEMORY_BASE + MEMORY_SIZE - 1);
+        this.pia = new Via6522(PIA_BASE);
+        this.acia = new Acia6551(ACIA_BASE);
+
+        bus.addCpu(cpu);
+        bus.addDevice(ram);
+        bus.addDevice(pia);
+        bus.addDevice(acia);
+
+        if (romFile != null) {
+            File romImage = new File(romFile);
+            if (romImage.canRead()) {
+                logger.info("Loading ROM image from file {}", romImage);
+                this.rom = Memory.makeROM(ROM_BASE, ROM_BASE + ROM_SIZE - 1, romImage);
+            } else {
+                logger.info("Default ROM file {} not found, loading empty R/W memory image.", romImage);
+                this.rom = Memory.makeRAM(ROM_BASE, ROM_BASE + ROM_SIZE - 1);
+            }
+        } else {
+            logger.info("No ROM file specified, loading empty R/W memory image.");
+            this.rom = Memory.makeRAM(ROM_BASE, ROM_BASE + ROM_SIZE - 1);
+        }
+
+        bus.addDevice(rom);
+    }
+
+    @Override
+    public Bus getBus() {
+        return bus;
+    }
+
+    @Override
+    public Cpu getCpu() {
+        return cpu;
+    }
+
+    @Override
+    public Memory getRam() {
+        return ram;
+    }
+
+    @Override
+    public Acia getAcia() {
+        return acia;
+    }
+
+    @Override
+    public Pia getPia() {
+        return pia;
+    }
+
+    @Override
+    public Crtc getCrtc() {
+        return null;
+    }
+
+    @Override
+    public Memory getRom() {
+        return rom;
+    }
+
+    @Override
+    public void setRom(Memory rom) throws MemoryRangeException {
+        if (this.rom != null) {
+            bus.removeDevice(this.rom);
+        }
+        this.rom = rom;
+        bus.addDevice(this.rom);
+    }
+
+    @Override
+    public int getRomBase() {
+        return ROM_BASE;
+    }
+
+    @Override
+    public int getRomSize() {
+        return ROM_SIZE;
+    }
+
+    @Override
+    public int getMemorySize() {
+        return MEMORY_SIZE;
+    }
+
+    @Override
+    public String getName() {
+        return "mike42";
+    }
+}

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

@@ -23,6 +23,7 @@
 
 package com.loomcom.symon.ui;
 
+import com.formdev.flatlaf.util.UIScale;
 import com.loomcom.symon.Breakpoints;
 import com.loomcom.symon.util.Utils;
 import org.slf4j.Logger;
@@ -40,7 +41,7 @@ public class BreakpointsWindow extends JFrame {
 
     private static final Logger logger = LoggerFactory.getLogger(BreakpointsWindow.class);
 
-    private static final Dimension FRAME_SIZE = new Dimension(240, 280);
+    private static final Dimension FRAME_SIZE = UIScale.scale(new Dimension(240, 280));
     private static final String EMPTY_STRING = "";
 
     private final JFrame mainWindow;
@@ -70,7 +71,6 @@ 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/MemoryWindow.java

@@ -23,6 +23,7 @@
 
 package com.loomcom.symon.ui;
 
+import com.formdev.flatlaf.util.UIScale;
 import com.loomcom.symon.Bus;
 import com.loomcom.symon.exceptions.MemoryAccessException;
 import com.loomcom.symon.util.Utils;
@@ -55,15 +56,15 @@ public class MemoryWindow extends JFrame implements ActionListener {
     private JButton previousPageButton;
     private JButton nextPageButton;
 
-    private static final Dimension MINIMUM_SIZE = new Dimension(320, 600);
+    private static final Dimension MINIMUM_SIZE = UIScale.scale(new Dimension(400, 600));
 
     // The width of column 0 (address), in pixels
-    private static final int ADDR_COL_WIDTH = 48;
+    private static final int ADDR_COL_WIDTH = UIScale.scale(64);
 
-    private static final int HEX_COL_WIDTH = 32;
+    private static final int HEX_COL_WIDTH = UIScale.scale(32);
 
     // The width of the ASCII cells, in pixels
-    private static final int ASCII_COL_WIDTH = 8;
+    private static final int ASCII_COL_WIDTH = UIScale.scale(15);
 
     // The start/end columns of the ASCII view
     private static final int ASCII_COL_START = 9;

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

@@ -23,17 +23,20 @@
 
 package com.loomcom.symon.ui;
 
+import com.formdev.flatlaf.util.UIScale;
 import com.loomcom.symon.Cpu;
 import com.loomcom.symon.CpuState;
+import com.loomcom.symon.devices.Pia;
+import com.loomcom.symon.devices.Via6522;
 import com.loomcom.symon.machines.Machine;
 
 import javax.swing.*;
 import javax.swing.border.Border;
 import javax.swing.border.EtchedBorder;
-import javax.swing.plaf.metal.MetalTextFieldUI;
 import java.awt.*;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
+import java.util.Objects;
 
 /**
  * UI component that displays the current state of the simulated CPU.
@@ -69,12 +72,14 @@ public class StatusPanel extends JPanel {
     private JTextField aField;
     private JTextField xField;
     private JTextField yField;
+    private JTextField piaBField;
+    private JTextField piaAField;
 
     private final Machine machine;
 
     private static final int EMPTY_BORDER = 10;
     private static final Border LABEL_BORDER = BorderFactory.createEmptyBorder(0, 5, 0, 0);
-    private static final Font LABEL_FONT = new Font(Font.SANS_SERIF, Font.BOLD, 12);
+    private static final Font LABEL_FONT = new Font(Font.SANS_SERIF, Font.BOLD, UIScale.scale(12));
     private static final Dimension LARGE_TEXT_FIELD_SIZE = new Dimension(134, 22);
     private static final Dimension SMALL_TEXT_FIELD_SIZE = new Dimension(65, 22);
 
@@ -86,7 +91,7 @@ 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));
@@ -99,20 +104,20 @@ public class StatusPanel extends JPanel {
         JPanel statusFlagsPanel = new JPanel();
         statusFlagsPanel.setAlignmentX(LEFT_ALIGNMENT);
 
-        carryOn = new ImageIcon(this.getClass().getResource("/C_on.png"));
+        carryOn = loadScaledIcon("/C_on.png");
-        carryOff = new ImageIcon(this.getClass().getResource("/C_off.png"));
+        carryOff = loadScaledIcon("/C_off.png");
-        zeroOn = new ImageIcon(this.getClass().getResource("/Z_on.png"));
+        zeroOn = loadScaledIcon("/Z_on.png");
-        zeroOff = new ImageIcon(this.getClass().getResource("/Z_off.png"));
+        zeroOff = loadScaledIcon("/Z_off.png");
-        irqOn = new ImageIcon(this.getClass().getResource("/I_on.png"));
+        irqOn = loadScaledIcon("/I_on.png");
-        irqOff = new ImageIcon(this.getClass().getResource("/I_off.png"));
+        irqOff = loadScaledIcon("/I_off.png");
-        decimalOn = new ImageIcon(this.getClass().getResource("/D_on.png"));
+        decimalOn = loadScaledIcon("/D_on.png");
-        decimalOff = new ImageIcon(this.getClass().getResource("/D_off.png"));
+        decimalOff = loadScaledIcon("/D_off.png");
-        breakOn = new ImageIcon(this.getClass().getResource("/B_on.png"));
+        breakOn = loadScaledIcon("/B_on.png");
-        breakOff = new ImageIcon(this.getClass().getResource("/B_off.png"));
+        breakOff = loadScaledIcon("/B_off.png");
-        overflowOn = new ImageIcon(this.getClass().getResource("/O_on.png"));
+        overflowOn = loadScaledIcon("/O_on.png");
-        overflowOff = new ImageIcon(this.getClass().getResource("/O_off.png"));
+        overflowOff = loadScaledIcon("/O_off.png");
-        negativeOn = new ImageIcon(this.getClass().getResource("/N_on.png"));
+        negativeOn = loadScaledIcon("/N_on.png");
-        negativeOff = new ImageIcon(this.getClass().getResource("/N_off.png"));
+        negativeOff = loadScaledIcon("/N_off.png");
 
         // Initialize all to off
         carryFlagLabel = new JLabel(carryOff, JLabel.CENTER);
@@ -125,16 +130,15 @@ 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);
@@ -152,6 +156,10 @@ public class StatusPanel extends JPanel {
         JLabel xLabel = makeLabel("X");
         JLabel yLabel = makeLabel("Y");
 
+        // PIA/VIA labels
+        JLabel piaBLabel = makeLabel("PB");
+        JLabel piaALabel = makeLabel("PA");
+
         statusFlagsLabel.setToolTipText("6502 Processor Status Flags");
         opcodeLabel.setToolTipText("Instruction Register");
         pcLabel.setToolTipText("Program Counter");
@@ -164,6 +172,9 @@ public class StatusPanel extends JPanel {
         xField = makeTextField(SMALL_TEXT_FIELD_SIZE, true);
         yField = makeTextField(SMALL_TEXT_FIELD_SIZE, true);
 
+        piaBField = makeTextField(LARGE_TEXT_FIELD_SIZE, false);
+        piaAField = makeTextField(LARGE_TEXT_FIELD_SIZE, false);
+
         // Make fields editable
         pcField.addActionListener(new ActionListener() {
             @Override
@@ -243,7 +254,6 @@ 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);
@@ -287,6 +297,25 @@ public class StatusPanel extends JPanel {
         add(xField, constraints);
         constraints.gridx = 1;
         add(yField, constraints);
+
+        constraints.insets = new Insets(5, 0, 0, 0);
+        constraints.gridx = 0;
+        constraints.gridwidth = 2;
+        constraints.gridy = 10;
+        add(piaBLabel, constraints);
+
+        constraints.insets = new Insets(2, 2, 2, 2);
+        constraints.gridy = 11;
+        add(piaBField, constraints);
+
+        constraints.insets = new Insets(5, 0, 0, 0);
+        constraints.gridy = 12;
+        add(piaALabel, constraints);
+
+        constraints.insets = new Insets(2, 2, 2, 2);
+        constraints.gridy = 13;
+        add(piaAField, constraints);
+
     }
 
     /**
@@ -296,6 +325,8 @@ public class StatusPanel extends JPanel {
         Cpu cpu = machine.getCpu();
         CpuState cpuState = cpu.getCpuState();
 
+        Pia pia = machine.getPia();
+
         // Update the Processor Status Flag display
         int status = cpuState.getStatusFlag();
 
@@ -317,6 +348,12 @@ public class StatusPanel extends JPanel {
         xField.setText(cpu.getXRegisterStatus());
         yField.setText(cpu.getYRegisterStatus());
 
+        // Update the Pia Variables
+        if (pia instanceof Via6522) {
+            piaBField.setText(((Via6522) pia).getPBStatus());
+            piaAField.setText(((Via6522) pia).getPAStatus());
+        }
+
         repaint();
     }
 
@@ -389,16 +426,11 @@ public class StatusPanel extends JPanel {
         JTextField textField = new JTextField("");
         textField.setAlignmentX(LEFT_ALIGNMENT);
         textField.setEditable(editable);
-        textField.setMinimumSize(size);
+
-        textField.setMaximumSize(size);
+        Dimension scaleSize = UIScale.scale(size);
-        textField.setPreferredSize(size);
+        textField.setMinimumSize(scaleSize);
-        textField.setBackground(Color.WHITE);
+        textField.setMaximumSize(scaleSize);
-        // Although we usually defer to the system look-and-feel, for
+        textField.setPreferredSize(scaleSize);
-        // 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;
     }
@@ -407,4 +439,14 @@ public class StatusPanel extends JPanel {
         String val = source.getText().replaceAll("[^0-9a-fA-F]", "");
         return Integer.parseInt(val, 16);
     }
+
+    private ImageIcon loadScaledIcon(String resourcePath) {
+        ImageIcon icon = new ImageIcon(Objects.requireNonNull(this.getClass().getResource(resourcePath)));
+
+        int scaledWidth = UIScale.scale(icon.getIconWidth());
+        int scaledHeight = UIScale.scale(icon.getIconHeight());
+
+        Image scaleImage = icon.getImage().getScaledInstance(scaledWidth, scaledHeight, Image.SCALE_SMOOTH);
+        return new ImageIcon(scaleImage);
+    }
 }

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

@@ -24,6 +24,7 @@
 
 package com.loomcom.symon.ui;
 
+import com.formdev.flatlaf.util.UIScale;
 import com.loomcom.symon.CpuState;
 import com.loomcom.symon.util.FifoRingBuffer;
 
@@ -39,8 +40,8 @@ public class TraceLog extends JFrame {
     private final FifoRingBuffer<CpuState> traceLog;
     private final JTextArea                    traceLogTextArea;
 
-    private static final Dimension MIN_SIZE       = new Dimension(320, 200);
+    private static final Dimension MIN_SIZE       = UIScale.scale(new Dimension(320, 200));
-    private static final Dimension PREFERRED_SIZE = new Dimension(640, 480);
+    private static final Dimension PREFERRED_SIZE = UIScale.scale(new Dimension(640, 480));
     private static final int       MAX_LOG_LENGTH = 50000;
 
     public TraceLog() {
@@ -53,7 +54,7 @@ public class TraceLog extends JFrame {
         setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
 
         traceLogTextArea = new JTextArea();
-        traceLogTextArea.setFont(new Font(Font.MONOSPACED, Font.BOLD, 12));
+        traceLogTextArea.setFont(new Font(Font.MONOSPACED, Font.BOLD, UIScale.scale(12)));
         traceLogTextArea.setEditable(false);
 
         JScrollPane scrollableView = new JScrollPane(traceLogTextArea);

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

@@ -0,0 +1,153 @@
+/*
+ * 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 com.loomcom.symon.machines.*;
+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 java.awt.*;
+import java.beans.PropertyChangeListener;
+import java.lang.reflect.InvocationTargetException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+
+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");
+
+        logger.debug("AWT Toolkit class: {}", Toolkit.getDefaultToolkit().getClass().getName());
+
+        // 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");
+
+        applyDetectedUiScale();
+
+        // 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", "Mike42" };
+        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 if (s != null && s.equals("Mike42")) {
+            return MichaelBillingtonMachine.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;
+    }
+
+    private static void applyDetectedUiScale() {
+        Double rawScale = null;
+
+        if (SystemInfo.isLinux) rawScale = X11ResourceReader.readXftDpiScale(); // ex: 1.5, 2.0, 2.5...
+
+        if (rawScale != null && rawScale > 1.0) {
+            // flatlaf.uiScale aceita frações — mantém a precisão original
+            System.setProperty("flatlaf.uiScale", rawScale + "x");
+
+            // sun.java2d.uiScale só aceita inteiros — arredonda para cima
+            int javaScale = (int) Math.ceil(rawScale);
+            //System.setProperty("sun.java2d.uiScale", String.valueOf(javaScale));
+
+            logger.debug("Detected scale {}x, applying flatlaf.uiScale={}x, sun.java2d.uiScale={}x",
+                    rawScale, rawScale, javaScale);
+        } else {
+            logger.debug("No X11 HiDPI scale detected, using default.");
+        }
+    }
+}

src/main/java/com/loomcom/symon/ui/X11ResourceReader.java

@@ -0,0 +1,54 @@
+package com.loomcom.symon.ui;
+
+import com.sun.jna.Library;
+import com.sun.jna.Native;
+import com.sun.jna.Pointer;
+import com.sun.jna.ptr.IntByReference;
+import com.sun.jna.ptr.PointerByReference;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class X11ResourceReader {
+
+    private final static Logger logger = LoggerFactory.getLogger(X11ResourceReader.class.getName());
+
+
+    public interface X11 extends Library {
+        X11 INSTANCE = Native.load("X11", X11.class);
+
+        Pointer XOpenDisplay(String display);
+        Pointer XResourceManagerString(Pointer display);
+        void XCloseDisplay(Pointer display);
+    }
+
+    public static Double readXftDpiScale() {
+        Pointer display = null;
+        try {
+            display = X11.INSTANCE.XOpenDisplay(null);
+            if (display == null) {
+                return null; // não conseguimos ligar ao X server (ex: Wayland puro sem XWayland)
+            }
+
+            Pointer resourceString = X11.INSTANCE.XResourceManagerString(display);
+            if (resourceString == null) {
+                return null;
+            }
+
+            String resources = resourceString.getString(0);
+            for (String line : resources.split("\n")) {
+                if (line.startsWith("Xft.dpi:")) {
+                    int dpi = Integer.parseInt(line.split(":")[1].trim());
+                    return Math.round((dpi / 96.0) * 4) / 4.0;
+                }
+            }
+            return null;
+        } catch (UnsatisfiedLinkError | Exception e) {
+            logger.debug("Could not read X11 resource manager (libX11 unavailable?)", e);
+            return null;
+        } finally {
+            if (display != null) {
+                X11.INSTANCE.XCloseDisplay(display);
+            }
+        }
+    }
+}

src/main/java/com/loomcom/symon/util/Utils.java

@@ -76,6 +76,16 @@ public class Utils {
                                            "F0", "F1", "F2", "F3", "F4", "F5", "F6", "F7",
                                            "F8", "F9", "FA", "FB", "FC", "FD", "FE", "FF"};
 
+    private static final String[] BIN_CONSTANTS = new String[256];
+
+    static {
+        for (int i = 0; i < 256; i++) {
+            String bin = Integer.toBinaryString(i);
+            // Left-pad to 8 digits with zeros
+            BIN_CONSTANTS[i] = "00000000".substring(bin.length()) + bin;
+        }
+    }
+
     /**
      * Very fast 8-bit int to ASCII conversion.
      *
@@ -116,4 +126,14 @@ public class Utils {
     public static int address(int lowByte, int hiByte) {
         return ((hiByte << 8) | lowByte) & 0xffff;
     }
+
+    /**
+     * Very fast 8-bit int to binary conversion, with zero-padded output.
+     *
+     * @param val The unsigned 8-bit value to convert to a zero padded binary string.
+     * @return Eight digit, zero padded binary string.
+     */
+    public static String byteToBin(int val) {
+        return BIN_CONSTANTS[val & 0xff];
+    }
 }

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