Tame Serial Monitor Memory & CPU Usage (Arduino issue #2233)

arduino/Arduino#2233

app/src/processing/app/SerialMonitor.java

@@ -19,6 +19,7 @@
 package processing.app;
 
 import processing.app.debug.MessageConsumer;
+import processing.app.debug.TextAreaFIFO;
 import processing.core.*;
 import static processing.app.I18n._;
 
@@ -32,17 +33,19 @@
 import java.net.*;
 import java.util.*;
 
-public class SerialMonitor extends JFrame implements MessageConsumer {
+public class SerialMonitor extends JFrame implements MessageConsumer,ActionListener {
   private Serial serial;
   private String port;
-  private JTextArea textArea;
+  private TextAreaFIFO textArea;
   private JScrollPane scrollPane;
   private JTextField textField;
   private JButton sendButton;
   private JCheckBox autoscrollBox;
   private JComboBox lineEndings;
   private JComboBox serialRates;
   private int serialRate;
+  private javax.swing.Timer updateTimer;
+  private StringBuffer updateBuffer;
 
   public SerialMonitor(String port) {
     super(port);
@@ -70,7 +73,9 @@ public void actionPerformed(ActionEvent e) {
     Font editorFont = Preferences.getFont("editor.font");
     Font font = new Font(consoleFont.getName(), consoleFont.getStyle(), editorFont.getSize());
 
-    textArea = new JTextArea(16, 40);
+    textArea = new TextAreaFIFO(4000000);
+    textArea.setRows(16);
+    textArea.setColumns(40);
     textArea.setEditable(false);    
     textArea.setFont(font);
 
@@ -174,6 +179,9 @@ public void actionPerformed(ActionEvent event) {
         }
       }
     }
+
+    updateBuffer = new StringBuffer(1048576);
+    updateTimer = new javax.swing.Timer(33, this);  // redraw serial monitor at 30 Hz
   }
 
   protected void setPlacement(int[] location) {
@@ -230,6 +238,7 @@ public void openSerialPort() throws SerialException {
       }
     }
     serial.addListener(this);
+    updateTimer.start();
   }
 
   public void closeSerialPort() {
@@ -243,15 +252,34 @@ public void closeSerialPort() {
     }
   }
 
-  public void message(final String s) {
-    SwingUtilities.invokeLater(new Runnable() {
-      public void run() {
-        textArea.append(s);
-        if (autoscrollBox.isSelected()) {
-        	textArea.setCaretPosition(textArea.getDocument().getLength());
-        }
-      }});
+  public void message(String s) {
+    // TODO: can we pass a byte array, to avoid overhead of String
+    addToUpdateBuffer(s);
+  }
+
+  private synchronized void addToUpdateBuffer(String s) {
+    updateBuffer.append(s);
+  }
+
+  private synchronized String consumeUpdateBuffer() {
+    String s = updateBuffer.toString();
+    updateBuffer.setLength(0);
+    return s;
+  }
+
+  public void actionPerformed(ActionEvent e) {
+    final String s = consumeUpdateBuffer();
+    if (s.length() > 0) {
+      //System.out.println("gui append " + s.length());
+      boolean scroll = autoscrollBox.isSelected();
+      textArea.allowTrim(scroll);
+      textArea.append(s);
+      if (scroll) {
+        textArea.setCaretPosition(textArea.getDocument().getLength());
+      }
+    }
   }
+
 }
 
 class FakeSerial extends Serial {

app/src/processing/app/debug/TextAreaFIFO.java

@@ -0,0 +1,55 @@
+// adapted from https://community.oracle.com/thread/1479784
+
+package processing.app.debug;
+
+import java.awt.*;
+import java.awt.event.*;
+import java.util.Date;
+import javax.swing.*;
+import javax.swing.event.*;
+import javax.swing.text.*;
+
+public class TextAreaFIFO extends JTextArea implements DocumentListener
+{
+	private int maxChars;
+	private int updateCount;  // limit how often we trim the document
+	private boolean doTrim;
+
+	public TextAreaFIFO(int max) {
+		maxChars = max;
+		updateCount = 0;
+		doTrim = true;
+		getDocument().addDocumentListener( this );
+	}
+
+	public void allowTrim(boolean trim) {
+		doTrim = trim;
+	}
+
+	public void insertUpdate(DocumentEvent e) {
+		if (++updateCount > 150 && doTrim) {
+			updateCount = 0;
+			SwingUtilities.invokeLater( new Runnable() {
+				public void run() {
+					trimDocument();
+				}
+			});
+		}
+	}
+
+	public void removeUpdate(DocumentEvent e) {}
+	public void changedUpdate(DocumentEvent e) {}
+
+	public void trimDocument() {
+		int len = 0;
+		len = getDocument().getLength();
+		if (len > maxChars) {
+			int n = len - maxChars;
+			System.out.println("trimDocument: remove " + n + " chars");
+			try {
+				getDocument().remove(0, n);
+			} catch(BadLocationException ble) {
+			}
+		}
+	}
+}