[TASK] Fix various exceptions

src/main/java/lu/jpt/csparqlproject/gui/FancyTextObserverWindow.java

@@ -4,6 +4,7 @@ import java.awt.BorderLayout;
 import java.awt.Color;
 import java.awt.Container;
 import java.awt.Dimension;
+import java.awt.EventQueue;
 import java.awt.Font;
 import java.awt.Insets;
 import java.awt.event.ActionEvent;
@@ -52,6 +53,7 @@ public class FancyTextObserverWindow extends JFrame implements Observer {
 	private JTextPane textPane;
 	private volatile boolean autoScrollToBottom = true;
 	private volatile boolean usePrefixManager = true;
+	private volatile boolean clearInsteadOfEleminatingLines = true;
 
 	/**
 	 * Constructor
@@ -70,6 +72,15 @@ public class FancyTextObserverWindow extends JFrame implements Observer {
 		this.autoScrollToBottom = autoScrollToBottom;
 	}
 	
+	/**
+	 * Set whether the window contents shall be cleared instead of being
+	 * maintained line by line to enforce a line limit.
+	 * @param clear
+	 */
+	public void setClearInsteadOfEliminatingLines(boolean clear) {
+		this.clearInsteadOfEleminatingLines = clear;
+	}
+	
 	/**
 	 * Set whether or not the PrefixManager shall be used to shorten
 	 * uris in strings to prefixes.
@@ -247,12 +258,25 @@ public class FancyTextObserverWindow extends JFrame implements Observer {
 	}
 
 	/**
-	 * Internal method to append text to the textpane
+	 * Internal man-in-the-middle method to pass the task to the AWT EventQueue
 	 * @param text to show within the window
 	 * @param addLinebreak whether or not to add a linebreak (usually yes is better)
 	 * @param color to display the text in
 	 */
 	private void appendToTextPane(String text, boolean addLinebreak, Color color) {
+		final FancyTextObserverWindow me = this;
+		EventQueue.invokeLater(() -> {
+			me.actuallyAppendTextToTextPane(text, addLinebreak, color);
+		});
+	}
+	
+	/**
+	 * Internal method to append text to the textpane
+	 * @param text to show within the window
+	 * @param addLinebreak whether or not to add a linebreak (usually yes is better)
+	 * @param color to display the text in
+	 */
+	private void actuallyAppendTextToTextPane(String text, boolean addLinebreak, Color color) {
 		if (addLinebreak) text += "\n";
 		StyleContext styleContext = StyleContext.getDefaultStyleContext();
 		AttributeSet attributeSet = styleContext.addAttribute(SimpleAttributeSet.EMPTY, StyleConstants.Foreground, color);
@@ -271,35 +295,47 @@ public class FancyTextObserverWindow extends JFrame implements Observer {
 			}
 		} while(!success);
 		// This is the place to enforce a line limit
-		//this.enforceLineLimit();
+		this.enforceLineLimit();
 		// TODO: Fix behaviour when autoscroll is disabled!
 		if(this.autoScrollToBottom) {
 			Document textPaneDocument = this.textPane.getDocument();
 			this.textPane.select(textPaneDocument.getLength(), textPaneDocument.getLength());
-		} 
+		}
 	}
-
+	
 	/**
 	 * Helper method to enforce a line limit for the window.
 	 */
 	private void enforceLineLimit() {
-		int MAX_LINES = 50;
+		int MAX_LINES = 300;
 		String[] lines = this.textPane.getText().split("\n");
 		int totalLines = lines.length;
 		int characters = 0;
 		if(totalLines > MAX_LINES) {
-			int linesToRemove = (totalLines - MAX_LINES) - 1;
-			if(linesToRemove > 5) {
-				for(int currentLine = 0; currentLine < linesToRemove; currentLine++) {
-					characters += lines[currentLine].length() + 1;
-				}
+			if(clearInsteadOfEleminatingLines) {
 				try {
-					this.textPane.getDocument().remove(0, characters);
+					this.textPane.getDocument().remove(0, this.textPane.getDocument().getLength());
 				} catch (BadLocationException e) {
-					FancyTextObserverWindow.logger.error(e.toString());
-					FancyTextObserverWindow.logger.error(e.getMessage());
+					// This has to work. :-/
+				}
+			} else {
+				int linesToRemove = (totalLines - MAX_LINES) - 1;
+				if(linesToRemove > 0) {
+					for(int currentLine = 0; currentLine < linesToRemove; currentLine++) {
+						characters += lines[currentLine].length() + 1;
+					}
+					try {
+						this.textPane.getDocument().remove(0, characters);
+					} catch (BadLocationException e) {
+						FancyTextObserverWindow.logger.error(e.toString());
+						FancyTextObserverWindow.logger.error(e.getMessage());
+					}
+					// Bonus: Update caret position
+					int length = this.textPane.getDocument().getLength();
+					this.textPane.setCaretPosition(length);
 				}
 			}
+
 		}
 	}