CRTC refactoring

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

@@ -65,6 +65,11 @@ public class Crtc extends Device {
 
     private int currentRegister = 0;
 
+    // Status bits
+    private boolean rowColumnAddressing = false;
+    private boolean displayEnableSkew = false;
+    private boolean cursorSkew = false;
+
     private Memory memory;
 
     public Crtc(int deviceAddress, Memory memory) throws MemoryRangeException, IOException {
@@ -118,8 +123,9 @@ public class Crtc extends Device {
         return null;
     }
 
-    public int[] getDmaAccess() {
+    public int getCharAtAddress(int address) throws MemoryAccessException {
-        return memory.getDmaAccess();
+        // TODO: Row/Column addressing
+        return memory.read(address);
     }
 
     public int getHorizontalDisplayed() {
@@ -162,6 +168,18 @@ public class Crtc extends Device {
         return pageSize;
     }
 
+    public boolean getRowColumnAddressing() {
+        return rowColumnAddressing;
+    }
+
+    public boolean getDisplayEnableSkew() {
+        return displayEnableSkew;
+    }
+
+    public boolean getCursorSkew() {
+        return cursorSkew;
+    }
+
     private void setCurrentRegister(int registerNumber) {
         this.currentRegister = registerNumber;
     }
@@ -180,7 +198,9 @@ public class Crtc extends Device {
                 pageSize = horizontalDisplayed * verticalDisplayed;
                 break;
             case MODE_CONTROL:
-                // TODO: Implement multiple addressing modes and cursor skew.
+                rowColumnAddressing = (data & 0x04) != 0;
+                displayEnableSkew = (data & 0x10) != 0;
+                cursorSkew = (data & 0x20) != 0;
                 break;
             case SCAN_LINE:
                 scanLinesPerRow = data;

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

@@ -25,6 +25,7 @@ package com.loomcom.symon.ui;
 
 import com.loomcom.symon.devices.Crtc;
 import com.loomcom.symon.devices.DeviceChangeListener;
+import com.loomcom.symon.exceptions.MemoryAccessException;
 
 import javax.swing.*;
 import java.awt.*;
@@ -36,8 +37,11 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
+import java.util.logging.Level;
 import java.util.logging.Logger;
 
+import static java.lang.System.*;
+
 /**
  * VideoWindow represents a graphics framebuffer backed by a 6545 CRTC.
  * Each time the window's VideoPanel is repainted, the video memory is
@@ -65,7 +69,6 @@ public class VideoWindow extends JFrame implements DeviceChangeListener {
 
     private BufferedImage image;
     private int[] charRom;
-    private int[] videoRam;
 
     private int horizontalDisplayed;
     private int verticalDisplayed;
@@ -85,17 +88,21 @@ public class VideoWindow extends JFrame implements DeviceChangeListener {
     private class VideoPanel extends JPanel {
         @Override
         public void paintComponent(Graphics g) {
-            for (int i = 0; i < crtc.getPageSize(); i++) {
+            try {
-                int address = crtc.getStartAddress() + i;
+                for (int i = 0; i < crtc.getPageSize(); i++) {
-                int originX = (i % horizontalDisplayed) * CHAR_WIDTH;
+                    int address = crtc.getStartAddress() + i;
-                int originY = (i / horizontalDisplayed) * scanLinesPerRow;
+                    int originX = (i % horizontalDisplayed) * CHAR_WIDTH;
-                image.getRaster().setPixels(originX, originY, CHAR_WIDTH, scanLinesPerRow, getGlyph(address));
+                    int originY = (i / horizontalDisplayed) * scanLinesPerRow;
+                    image.getRaster().setPixels(originX, originY, CHAR_WIDTH, scanLinesPerRow, getGlyph(address));
+                }
+                Graphics2D g2d = (Graphics2D) g;
+                if (shouldScale) {
+                    g2d.scale(scaleX, scaleY);
+                }
+                g2d.drawImage(image, 0, 0, null);
+            } catch (MemoryAccessException ex) {
+                logger.log(Level.SEVERE, "Memory Access Exception, can't paint video window! " + ex.getMessage());
             }
-            Graphics2D g2d = (Graphics2D)g;
-            if (shouldScale) {
-                g2d.scale(scaleX, scaleY);
-            }
-            g2d.drawImage(image, 0, 0, null);
         }
 
         @Override
@@ -132,7 +139,6 @@ public class VideoWindow extends JFrame implements DeviceChangeListener {
         this.scheduler = Executors.newSingleThreadScheduledExecutor();
         this.crtc = crtc;
         this.charRom = loadCharRom("/pet.rom");
-        this.videoRam = crtc.getDmaAccess();
         this.scaleX = scaleX;
         this.scaleY = scaleY;
         this.shouldScale = (scaleX > 1 || scaleY > 1);
@@ -158,13 +164,6 @@ public class VideoWindow extends JFrame implements DeviceChangeListener {
 
     }
 
-    public void refreshDisplay() {
-        // TODO: Verify whether this is necessary. Does `repaint()' do anything if the window is not visible?
-        if (isVisible()) {
-            repaint();
-        }
-    }
-
     /**
      * Called by the CRTC on state change.
      */
@@ -239,15 +238,13 @@ public class VideoWindow extends JFrame implements DeviceChangeListener {
      * @param address The address of the character being requested.
      * @return An array of integers representing the pixel data.
      */
-    private int[] getGlyph(int address) {
+    private int[] getGlyph(int address) throws MemoryAccessException {
-        int chr = videoRam[address];
+        int chr = crtc.getCharAtAddress(address);
         int romOffset = (chr & 0xff) * (CHAR_HEIGHT * CHAR_WIDTH);
         int[] glyph = new int[CHAR_WIDTH * scanLinesPerRow];
 
         // Populate the character
-        for (int i = 0; i < (CHAR_WIDTH * Math.min(CHAR_HEIGHT, scanLinesPerRow)); i++) {
+        arraycopy(charRom, romOffset, glyph, 0, CHAR_WIDTH * Math.min(CHAR_HEIGHT, scanLinesPerRow));
-            glyph[i] = charRom[romOffset + i];
-        }
 
         // Overlay the cursor
         if (!hideCursor && crtc.isCursorEnabled() && crtc.getCursorPosition() == address) {

src/test/java/com/loomcom/symon/CrtcTest.java

@@ -19,19 +19,17 @@ import static org.mockito.Mockito.*;
 public class CrtcTest {
 
     Crtc crtc;
+    Memory memory;
 
     @Mock
     DeviceChangeListener changeListener;
-    @Mock
-    Memory memory;
 
     @Before
     public void createDevices() throws Exception {
+        memory = new Memory(0, 0x7fff);
+
         crtc = new Crtc(0x9000, memory);
         crtc.registerListener(changeListener);
-
-        when(memory.startAddress()).thenReturn(0);
-        when(memory.endAddress()).thenReturn(0x7fff);
     }
 
     @Test
@@ -340,4 +338,58 @@ public class CrtcTest {
         crtc.write(1, 0x80); // Can't position cursor
     }
 
+    @Test
+    public void shouldSetRowColumnAddressing() throws Exception {
+        assertEquals(false, crtc.getRowColumnAddressing());
+        crtc.write(0, 8);        // Select mode control register
+        crtc.write(1, 0x04);
+        assertEquals(true, crtc.getRowColumnAddressing());
+    }
+
+    @Test
+    public void shouldSetDisplayEnableSkew() throws Exception {
+        assertEquals(false, crtc.getDisplayEnableSkew());
+        crtc.write(0, 8);        // Select mode control register
+        crtc.write(1, 0x10);
+        assertEquals(true, crtc.getDisplayEnableSkew());
+    }
+
+    @Test
+    public void shouldSetCursorSkew() throws Exception {
+        assertEquals(false, crtc.getCursorSkew());
+        crtc.write(0, 8);        // Select mode control register
+        crtc.write(1, 0x20);
+        assertEquals(true, crtc.getCursorSkew());
+    }
+
+    @Test
+    public void shouldDoStraightBinaryAddressing() throws Exception {
+        crtc.write(0, 8);
+        crtc.write(1, 0); // Select straight binary addressing
+
+        // Fill the memory with a repeating pattern
+        int videoMemoryBase = 0x7000;
+        int j = 0;
+
+        for (int i = 0; i < 2048; i++) {
+            memory.write(videoMemoryBase + i, j);
+            if (j == 255) {
+                j = 0;
+            } else {
+                j++;
+            }
+        }
+
+        // Now verify that straight-binary addressing of the CRTC works
+        j = 0;
+
+        for (int i = 0; i < 2048; i++) {
+            assertEquals(j, crtc.getCharAtAddress(videoMemoryBase + i));
+            if (j == 255) {
+                j = 0;
+            } else {
+                j++;
+            }
+        }
+    }
 }