Set 'step' location for debugger

[bsutton]

So I've got a little scripting language for a robotic arm and I'm trying to implement the ability to 'step' through the code.

I need to highlight the current line that the 'debug stepper' is currently on.

I've been trying to adapt code which implements a green arrow to indicate a break point.
The problem is that the code always moves the green arrow to the 'current cursor' location within a CodeArea.

I need to be able to 'select' the line using a 'next step' button.

The pertinent code is:

            scriptEditor = new CodeArea();

                numberFactory = LineNumberFactory.get(scriptEditor);
                IntFunction<Node> arrowFactory = new ArrowFactory(scriptEditor.currentParagraphProperty());
                IntFunction<Node> graphicFactory = line -> {
                    HBox hbox = new HBox(numberFactory.apply(line), arrowFactory.apply(line));
                    hbox.setAlignment(Pos.CENTER_LEFT);
                    return hbox;
                };

                scriptEditor.setParagraphGraphicFactory(graphicFactory);

and the arrow function:

class ArrowFactory implements IntFunction<Node>
    {
        private final ObservableValue<Integer> shownLine;

        ArrowFactory(ObservableValue<Integer> shownLine)
        {
            this.shownLine = shownLine;
        }

        @Override
        public Node apply(int lineNumber)
        {
            Polygon triangle = new Polygon(0.0, 0.0, 10.0, 5.0, 0.0, 10.0);
            triangle.setFill(Color.GREEN);

            ObservableValue<Boolean> visible = Val.map(shownLine, sl -> sl == lineNumber);

            triangle.visibleProperty().bind(Val.flatMap(triangle.sceneProperty(), scene -> {
                return scene != null ? visible : Val.constant(false);
            }));

            return triangle;
        }
    }

I've played with the 'lineNumber' changing it to use a field which contains the current 'step line' but this just results in every line getting an arrow as I step through the code.

Any assistance would be greatly appreciated.

The full class is:

package controller;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.net.URL;
import java.nio.file.Files;
import java.time.Duration;
import java.util.Collection;
import java.util.Collections;
import java.util.Optional;
import java.util.ResourceBundle;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeoutException;
import java.util.function.IntFunction;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Stream;

import javafx.application.Platform;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.geometry.Pos;
import javafx.scene.Node;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.ButtonType;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Polygon;
import javafx.stage.FileChooser;

import org.fxmisc.richtext.CodeArea;
import org.fxmisc.richtext.LineNumberFactory;
import org.fxmisc.richtext.PlainTextChange;
import org.fxmisc.richtext.StyleSpans;
import org.fxmisc.richtext.StyleSpansBuilder;
import org.reactfx.EventStream;
import org.reactfx.util.Try;
import org.reactfx.value.Val;

import robot.IllegalCommandException;
import robot.InvaidMotorFrequency;
import robot.InvalidMotorConfiguration;
import robot.InvalidMotorException;
import robot.NotConnectedException;
import robot.iRobot;
import application.iDisplay;

public class ScriptController implements iController, Initializable
{

    private static final String[] KEYWORDS = new String[]
    { "mov", "on", "set", "wait", "stop" };

    private static final String KEYWORD_PATTERN = "\\b(" + String.join("|", KEYWORDS) + ")\\b";
    private static final String COMMENT_PATTERN = "//[^\n]*" + "|" + "/\\*(.|\\R)*?\\*/";

    private static final Pattern PATTERN = Pattern.compile("(?<KEYWORD>" + KEYWORD_PATTERN + ")" + "|(?<COMMENT>"
            + COMMENT_PATTERN + ")");
    @FXML
    TextArea scriptEditorPlaceHolder;

    CodeArea scriptEditor;
    private ExecutorService executor;

    @FXML
    HBox nextCmdLine;

    @FXML
    TextField nextCmd;

    private File activeFile = null;
    private iDisplay display;
    private iRobot robot;
    private File lastDir;

    private MainUIController mainController;

    private int currentStep = 0;

    private IntFunction<Node> numberFactory;

    @Override
    public void init(MainUIController mainController, iDisplay display)
    {
        this.mainController = mainController;

        this.display = display;
        this.robot = mainController.getRobot();
        this.lastDir = robot.getLastSaveDirectory();

        VBox parent = (VBox) scriptEditorPlaceHolder.getParent();

        int pos = 0;
        for (Node child : parent.getChildrenUnmodifiable())
        {
            if (child == scriptEditorPlaceHolder)
            {
                parent.getChildren().remove(child);
                executor = Executors.newSingleThreadExecutor();

                scriptEditor = new CodeArea();

                numberFactory = LineNumberFactory.get(scriptEditor);
                IntFunction<Node> arrowFactory = new ArrowFactory(scriptEditor.currentParagraphProperty());
                IntFunction<Node> graphicFactory = line -> {
                    HBox hbox = new HBox(numberFactory.apply(line), arrowFactory.apply(line));
                    hbox.setAlignment(Pos.CENTER_LEFT);
                    return hbox;
                };

                scriptEditor.setParagraphGraphicFactory(graphicFactory);

                scriptEditor.textProperty().addListener(
                        (obs, oldText, newText) -> {
                            scriptEditor.setStyleSpans(0, computeHighlighting(newText));

                            EventStream<PlainTextChange> textChanges = scriptEditor.plainTextChanges();
                            textChanges.successionEnds(Duration.ofMillis(500))
                                    .supplyTask(this::computeHighlightingAsync).awaitLatest(textChanges).map(Try::get)
                                    .subscribe(this::applyHighlighting);
                        });

                VBox.setVgrow(scriptEditor, Priority.ALWAYS);
                parent.getChildren().add(pos, scriptEditor);
                break;
            }
        }

    }

    private Task<StyleSpans<Collection<String>>> computeHighlightingAsync()
    {
        String text = scriptEditor.getText();
        Task<StyleSpans<Collection<String>>> task = new Task<StyleSpans<Collection<String>>>()
        {
            @Override
            protected StyleSpans<Collection<String>> call() throws Exception
            {
                return computeHighlighting(text);
            }
        };
        executor.execute(task);
        return task;
    }

    private void applyHighlighting(StyleSpans<Collection<String>> highlighting)
    {
        scriptEditor.setStyleSpans(0, highlighting);
    }

    private static StyleSpans<Collection<String>> computeHighlighting(String text)
    {
        Matcher matcher = PATTERN.matcher(text);
        int lastKwEnd = 0;
        StyleSpansBuilder<Collection<String>> spansBuilder = new StyleSpansBuilder<>();
        while (matcher.find())
        {
            String styleClass = matcher.group("KEYWORD") != null ? "keyword"

            : matcher.group("COMMENT") != null ? "comment" : null; /*
                                                                     * never
                                                                     * happens
                                                                     */
            assert styleClass != null;
            spansBuilder.add(Collections.emptyList(), matcher.start() - lastKwEnd);
            spansBuilder.add(Collections.singleton(styleClass), matcher.end() - matcher.start());
            lastKwEnd = matcher.end();
        }
        spansBuilder.add(Collections.emptyList(), text.length() - lastKwEnd);
        return spansBuilder.create();
    }

    @Override
    public void initialize(URL location, ResourceBundle resources)
    {
        nextCmdLine.setDisable(true);

    }

    @FXML
    void onOpen(ActionEvent event)
    {
        // Create a file chooser
        final FileChooser fc = new FileChooser();
        fc.setInitialDirectory(lastDir);
        FileChooser.ExtensionFilter filter = new FileChooser.ExtensionFilter("Robot Move files", "rmf");
        fc.setSelectedExtensionFilter(filter);

        // In response to a button click:
        File openedFile = fc.showOpenDialog(null);

        if (openedFile != null)
        {
            try
            {
                activeFile = openedFile;
                lastDir = activeFile.getParentFile();
                robot.setLastSaveDirectory(fc.getInitialDirectory());

                scriptEditor.clear();
                try (Stream<String> lines = Files.lines(activeFile.toPath()))
                {
                    lines.forEach(s -> scriptEditor.appendText(s + "\n"));
                }
            }
            catch (IOException e)
            {
                display.showException(e);
            }
        }

    }

    @FXML
    void onSave(ActionEvent event)
    {
        if (activeFile != null)
        {
            BufferedWriter writer;
            try
            {
                writer = new BufferedWriter(new FileWriter(activeFile));
                writer.write(scriptEditor.getText());
                writer.close();
            }
            catch (IOException e)
            {
                display.showException(e);
            }

        }
        else
            onSaveAs(event);

    }

    @FXML
    void onSaveAs(ActionEvent event)
    {
        // Create a file chooser
        final FileChooser fc = new FileChooser();
        fc.setInitialDirectory(lastDir);
        FileChooser.ExtensionFilter filter = new FileChooser.ExtensionFilter("Robot Move files", "rmf");
        fc.setSelectedExtensionFilter(filter);
        // In response to a button click:
        File savedFile = fc.showSaveDialog(null);

        if (savedFile != null)
        {
            activeFile = savedFile;
            lastDir = activeFile.getParentFile();
            if (!activeFile.getName().endsWith(".rmf"))
                activeFile = new File(activeFile.getParentFile(), activeFile.getName() + ".rmf");
            onSave(event);
            robot.setLastSaveDirectory(fc.getInitialDirectory());
        }

    }

    @FXML
    void onNew(ActionEvent event)
    {
        Alert alert = new Alert(AlertType.CONFIRMATION);
        alert.setTitle("Confirm New action");
        alert.setHeaderText(null);
        alert.setContentText("Are you sure? You will loose any unsaved changes");

        Optional<ButtonType> result = alert.showAndWait();
        if (result.get() == ButtonType.OK)
        {
            activeFile = null;
            scriptEditor.clear();
        }
    }

    @FXML
    void onRun(ActionEvent event)
    {
        runSequence(scriptEditor.getText());
    }

    @FXML
    void onRestart(ActionEvent event)
    {
        currentStep = 0;
        scriptEditor.setStyleClass(0, scriptEditor.getText().length(), "black");
    }

    @FXML
    void onStep(ActionEvent event)
    {
        // not very efficient but means we can handle editing whilst stepping
        String[] cmds = scriptEditor.getText().split("\n");

        if (currentStep == cmds.length)
        {
            scriptEditor.setStyleClass(0, scriptEditor.getText().length(), "black");
            display.showMessage("Sequence complete. Resetting to start");
            currentStep = 0;
        }
        else
        {
            int startCharacter = 0;
            int endCharacter = cmds[0].length();
            // determine character position of current step
            for (int i = 1; i <= currentStep; i++)
            {
                startCharacter = endCharacter + 1;
                endCharacter += cmds[i].length() + 1;
            }

            String cmd = cmds[currentStep].trim();

            scriptEditor.setStyleClass(0, startCharacter, "black");
            scriptEditor.setStyleClass(startCharacter, endCharacter, "blue");
            // scriptEditor.setStyle(startCharacter, endCharacter,
            // "-fx-strikethrough");

            // First time step is click we prime the pump
            if (currentStep >= 0)
            {
                // stepSequence(cmd);
            }

            currentStep++;
            this.nextCmd.setText(cmd);
        }
    }

    private void stepSequence(String nextCommand)
    {
        try
        {
            this.robot.sendCmd(nextCommand, display);
        }
        catch (Exception e1)
        {
            display.showException(e1);
        }
    }

    public void runSequence(String text)
    {
        if (!robot.isConnected())
            this.display.showError("Device is not connected");
        else
        {
            // push into the background so we don't lock the UI.
            ExecutorService executor = Executors.newSingleThreadExecutor();
            executor.submit(() -> {
                try
                {
                    String[] cmds = text.split("\n");

                    int line = 1;
                    for (String cmd : cmds)
                    {
                        scriptEditor.setStyleClass(line, line, ".step-highlite");

                        if (cmd != null)
                            this.robot.sendCmd(cmd.trim(), display);
                        line++;
                    }

                    Platform.runLater(() -> this.display.append("Sequence sent in full\n"));
                }
                catch (NotConnectedException | IOException | TimeoutException | InvalidMotorConfiguration
                        | InvaidMotorFrequency | InvalidMotorException | IllegalCommandException e)
                {
                    Platform.runLater(() -> display.showException(e));
                }
            });
        }

    }

    class ArrowFactory implements IntFunction<Node>
    {
        private final ObservableValue<Integer> shownLine;

        ArrowFactory(ObservableValue<Integer> shownLine)
        {
            this.shownLine = shownLine;
        }

        @Override
        public Node apply(int lineNumber)
        {
            Polygon triangle = new Polygon(0.0, 0.0, 10.0, 5.0, 0.0, 10.0);
            triangle.setFill(Color.GREEN);

            ObservableValue<Boolean> visible = Val.map(shownLine, sl -> sl == lineNumber);

            triangle.visibleProperty().bind(Val.flatMap(triangle.sceneProperty(), scene -> {
                return scene != null ? visible : Val.constant(false);
            }));

            return triangle;
        }
    }
}

[TomasMikula]

Hi Brett,

you need to change this line

IntFunction<Node> arrowFactory = new ArrowFactory(scriptEditor.currentParagraphProperty());

to

IntFunction<Node> arrowFactory = new ArrowFactory(currentStep);

That requires you to make currentStep a property.

[bsutton]

Got it working so thanks for the prompt answer.

For the record here are the required changes.

currentStep become:
CurrentStep currentStep = new CurrentStep();

The Arrow is constructed as:
IntFunction arrowFactory = new ArrowFactory(currentStep);

I had to implement an observable for Current Step as:

    class CurrentStep implements ObservableValue<Integer>
    {
        private HashMap<ChangeListener<? super Integer>, ChangeListener<? super Integer>> changeListeners = new HashMap<>();

        private HashMap<InvalidationListener, InvalidationListener> invalidateListeners = new HashMap<>();

        private int value = 0;

        public void setValue(int value)
        {
            int oldValue = this.value;
            this.value = value;

            if (value == -1)
            {
                if (oldValue != -1)
                    for (InvalidationListener listener : invalidateListeners.values())
                    {
                        listener.invalidated(this);
                    }
            }
            else
                for (ChangeListener<? super Integer> listener : changeListeners.values())
                {
                    listener.changed(this, oldValue, value);
                }
        }

        public int get()
        {
            return value;
        }

        @Override
        public void addListener(ChangeListener<? super Integer> listener)
        {
            changeListeners.put(listener, listener);

        }

        @Override
        public void removeListener(ChangeListener<? super Integer> listener)
        {
            changeListeners.remove(listener);

        }

        @Override
        public Integer getValue()
        {
            return new Integer(value);
        }

        @Override
        public void addListener(InvalidationListener listener)
        {
            invalidateListeners.put(listener, listener);
        }

        @Override
        public void removeListener(InvalidationListener listener)
        {
            invalidateListeners.remove(listener);

        }
    };

The full code is:

package controller;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.net.URL;
import java.nio.file.Files;
import java.time.Duration;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Optional;
import java.util.ResourceBundle;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeoutException;
import java.util.function.IntFunction;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Stream;

import javafx.application.Platform;
import javafx.beans.InvalidationListener;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.geometry.Pos;
import javafx.scene.Node;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.ButtonType;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Polygon;
import javafx.stage.FileChooser;

import org.fxmisc.richtext.CodeArea;
import org.fxmisc.richtext.LineNumberFactory;
import org.fxmisc.richtext.PlainTextChange;
import org.fxmisc.richtext.StyleSpans;
import org.fxmisc.richtext.StyleSpansBuilder;
import org.reactfx.EventStream;
import org.reactfx.util.Try;
import org.reactfx.value.Val;

import robot.IllegalCommandException;
import robot.InvaidMotorFrequency;
import robot.InvalidMotorConfiguration;
import robot.InvalidMotorException;
import robot.NotConnectedException;
import robot.iRobot;
import application.iDisplay;

public class ScriptController implements iController, Initializable
{

    private static final String[] KEYWORDS = new String[]
    { "mov", "on", "set", "wait", "stop" };

    private static final String KEYWORD_PATTERN = "\\b(" + String.join("|", KEYWORDS) + ")\\b";
    private static final String COMMENT_PATTERN = "//[^\n]*" + "|" + "/\\*(.|\\R)*?\\*/";

    private static final Pattern PATTERN = Pattern.compile("(?<KEYWORD>" + KEYWORD_PATTERN + ")" + "|(?<COMMENT>"
            + COMMENT_PATTERN + ")");
    @FXML
    TextArea scriptEditorPlaceHolder;

    CodeArea scriptEditor;
    private ExecutorService executor;

    @FXML
    HBox nextCmdLine;

    @FXML
    TextField nextCmd;

    private File activeFile = null;
    private iDisplay display;
    private iRobot robot;
    private File lastDir;

    CurrentStep currentStep = new CurrentStep();

    private MainUIController mainController;

    private IntFunction<Node> numberFactory;

    @Override
    public void init(MainUIController mainController, iDisplay display)
    {
        this.mainController = mainController;

        this.display = display;
        this.robot = mainController.getRobot();
        this.lastDir = robot.getLastSaveDirectory();

        VBox parent = (VBox) scriptEditorPlaceHolder.getParent();

        int pos = 0;
        for (Node child : parent.getChildrenUnmodifiable())
        {
            if (child == scriptEditorPlaceHolder)
            {
                parent.getChildren().remove(child);
                executor = Executors.newSingleThreadExecutor();

                scriptEditor = new CodeArea();

                numberFactory = LineNumberFactory.get(scriptEditor);
                IntFunction<Node> arrowFactory = new ArrowFactory(currentStep);
                IntFunction<Node> graphicFactory = line -> {
                    HBox hbox = new HBox(numberFactory.apply(line), arrowFactory.apply(line));
                    hbox.setAlignment(Pos.CENTER_LEFT);
                    return hbox;
                };

                scriptEditor.setParagraphGraphicFactory(graphicFactory);

                scriptEditor.textProperty().addListener(
                        (obs, oldText, newText) -> {
                            scriptEditor.setStyleSpans(0, computeHighlighting(newText));

                            EventStream<PlainTextChange> textChanges = scriptEditor.plainTextChanges();
                            textChanges.successionEnds(Duration.ofMillis(500))
                                    .supplyTask(this::computeHighlightingAsync).awaitLatest(textChanges).map(Try::get)
                                    .subscribe(this::applyHighlighting);
                        });

                VBox.setVgrow(scriptEditor, Priority.ALWAYS);
                parent.getChildren().add(pos, scriptEditor);
                break;
            }
        }

    }

    private Task<StyleSpans<Collection<String>>> computeHighlightingAsync()
    {
        String text = scriptEditor.getText();
        Task<StyleSpans<Collection<String>>> task = new Task<StyleSpans<Collection<String>>>()
        {
            @Override
            protected StyleSpans<Collection<String>> call() throws Exception
            {
                return computeHighlighting(text);
            }
        };
        executor.execute(task);
        return task;
    }

    private void applyHighlighting(StyleSpans<Collection<String>> highlighting)
    {
        scriptEditor.setStyleSpans(0, highlighting);
    }

    private static StyleSpans<Collection<String>> computeHighlighting(String text)
    {
        Matcher matcher = PATTERN.matcher(text);
        int lastKwEnd = 0;
        StyleSpansBuilder<Collection<String>> spansBuilder = new StyleSpansBuilder<>();
        while (matcher.find())
        {
            String styleClass = matcher.group("KEYWORD") != null ? "keyword"

            : matcher.group("COMMENT") != null ? "comment" : null; /*
                                                                     * never
                                                                     * happens
                                                                     */
            assert styleClass != null;
            spansBuilder.add(Collections.emptyList(), matcher.start() - lastKwEnd);
            spansBuilder.add(Collections.singleton(styleClass), matcher.end() - matcher.start());
            lastKwEnd = matcher.end();
        }
        spansBuilder.add(Collections.emptyList(), text.length() - lastKwEnd);
        return spansBuilder.create();
    }

    @Override
    public void initialize(URL location, ResourceBundle resources)
    {
        nextCmdLine.setDisable(true);

    }

    @FXML
    void onOpen(ActionEvent event)
    {
        // Create a file chooser
        final FileChooser fc = new FileChooser();
        fc.setInitialDirectory(lastDir);
        FileChooser.ExtensionFilter filter = new FileChooser.ExtensionFilter("Robot Move files", "rmf");
        fc.setSelectedExtensionFilter(filter);

        // In response to a button click:
        File openedFile = fc.showOpenDialog(null);

        if (openedFile != null)
        {
            try
            {
                activeFile = openedFile;
                lastDir = activeFile.getParentFile();
                robot.setLastSaveDirectory(fc.getInitialDirectory());

                scriptEditor.clear();
                try (Stream<String> lines = Files.lines(activeFile.toPath()))
                {
                    lines.forEach(s -> scriptEditor.appendText(s + "\n"));
                }
            }
            catch (IOException e)
            {
                display.showException(e);
            }
        }

    }

    @FXML
    void onSave(ActionEvent event)
    {
        if (activeFile != null)
        {
            BufferedWriter writer;
            try
            {
                writer = new BufferedWriter(new FileWriter(activeFile));
                writer.write(scriptEditor.getText());
                writer.close();
            }
            catch (IOException e)
            {
                display.showException(e);
            }

        }
        else
            onSaveAs(event);

    }

    @FXML
    void onSaveAs(ActionEvent event)
    {
        // Create a file chooser
        final FileChooser fc = new FileChooser();
        fc.setInitialDirectory(lastDir);
        FileChooser.ExtensionFilter filter = new FileChooser.ExtensionFilter("Robot Move files", "rmf");
        fc.setSelectedExtensionFilter(filter);
        // In response to a button click:
        File savedFile = fc.showSaveDialog(null);

        if (savedFile != null)
        {
            activeFile = savedFile;
            lastDir = activeFile.getParentFile();
            if (!activeFile.getName().endsWith(".rmf"))
                activeFile = new File(activeFile.getParentFile(), activeFile.getName() + ".rmf");
            onSave(event);
            robot.setLastSaveDirectory(fc.getInitialDirectory());
        }

    }

    @FXML
    void onNew(ActionEvent event)
    {
        Alert alert = new Alert(AlertType.CONFIRMATION);
        alert.setTitle("Confirm New action");
        alert.setHeaderText(null);
        alert.setContentText("Are you sure? You will loose any unsaved changes");

        Optional<ButtonType> result = alert.showAndWait();
        if (result.get() == ButtonType.OK)
        {
            activeFile = null;
            scriptEditor.clear();
        }
    }

    @FXML
    void onRun(ActionEvent event)
    {
        runSequence(scriptEditor.getText());
    }

    @FXML
    void onRestart(ActionEvent event)
    {
        currentStep.setValue(0);
        scriptEditor.setStyleClass(0, scriptEditor.getText().length(), "black");
    }

    @FXML
    void onStep(ActionEvent event)
    {
        // not very efficient but means we can handle editing whilst stepping
        String[] cmds = scriptEditor.getText().split("\n");

        if (currentStep.get() == cmds.length)
        {
            scriptEditor.setStyleClass(0, scriptEditor.getText().length(), "black");
            display.showMessage("Sequence complete. Resetting to start");
            currentStep.setValue(0);
        }
        else
        {
            int startCharacter = 0;
            int endCharacter = cmds[0].length();
            // determine character position of current step
            for (int i = 1; i <= currentStep.get(); i++)
            {
                startCharacter = endCharacter + 1;
                endCharacter += cmds[i].length() + 1;
            }

            String cmd = cmds[currentStep.get()].trim();

            scriptEditor.setStyleClass(0, startCharacter, "black");
            scriptEditor.setStyleClass(startCharacter, endCharacter, "blue");
            // scriptEditor.setStyle(startCharacter, endCharacter,
            // "-fx-strikethrough");

            // First time step is click we prime the pump
            if (currentStep.get() >= 0)
            {
                stepSequence(cmd);
            }

            currentStep.setValue(currentStep.get() + 1);
            this.nextCmd.setText(cmd);
        }
    }

    private void stepSequence(String nextCommand)
    {
        try
        {
            this.robot.sendCmd(nextCommand, display);
        }
        catch (Exception e1)
        {
            display.showException(e1);
        }
    }

    public void runSequence(String text)
    {
        if (!robot.isConnected())
            this.display.showError("Device is not connected");
        else
        {
            // push into the background so we don't lock the UI.
            ExecutorService executor = Executors.newSingleThreadExecutor();
            executor.submit(() -> {
                try
                {
                    String[] cmds = text.split("\n");

                    int line = 1;
                    for (String cmd : cmds)
                    {
                        scriptEditor.setStyleClass(line, line, ".step-highlite");

                        if (cmd != null)
                            this.robot.sendCmd(cmd.trim(), display);
                        line++;
                    }

                    Platform.runLater(() -> this.display.append("Sequence sent in full\n"));
                }
                catch (NotConnectedException | IOException | TimeoutException | InvalidMotorConfiguration
                        | InvaidMotorFrequency | InvalidMotorException | IllegalCommandException e)
                {
                    Platform.runLater(() -> display.showException(e));
                }
            });
        }

    }

    class ArrowFactory implements IntFunction<Node>
    {
        private final ObservableValue<Integer> shownLine;

        ArrowFactory(ObservableValue<Integer> shownLine)
        {
            this.shownLine = shownLine;
        }

        @Override
        public Node apply(int lineNumber)
        {
            Polygon triangle = new Polygon(0.0, 0.0, 10.0, 5.0, 0.0, 10.0);
            triangle.setFill(Color.GREEN);

            ObservableValue<Boolean> visible = Val.map(shownLine, sl -> sl == lineNumber);

            triangle.visibleProperty().bind(Val.flatMap(triangle.sceneProperty(), scene -> {
                return scene != null ? visible : Val.constant(false);
            }));

            return triangle;
        }
    }

    class CurrentStep implements ObservableValue<Integer>
    {
        private HashMap<ChangeListener<? super Integer>, ChangeListener<? super Integer>> changeListeners = new HashMap<>();

        private HashMap<InvalidationListener, InvalidationListener> invalidateListeners = new HashMap<>();

        private int value = 0;

        public void setValue(int value)
        {
            int oldValue = this.value;
            this.value = value;

            if (value == -1)
            {
                if (oldValue != -1)
                    for (InvalidationListener listener : invalidateListeners.values())
                    {
                        listener.invalidated(this);
                    }
            }
            else
                for (ChangeListener<? super Integer> listener : changeListeners.values())
                {
                    listener.changed(this, oldValue, value);
                }
        }

        public int get()
        {
            return value;
        }

        @Override
        public void addListener(ChangeListener<? super Integer> listener)
        {
            changeListeners.put(listener, listener);

        }

        @Override
        public void removeListener(ChangeListener<? super Integer> listener)
        {
            changeListeners.remove(listener);

        }

        @Override
        public Integer getValue()
        {
            return new Integer(value);
        }

        @Override
        public void addListener(InvalidationListener listener)
        {
            invalidateListeners.put(listener, listener);
        }

        @Override
        public void removeListener(InvalidationListener listener)
        {
            invalidateListeners.remove(listener);

        }
    };

}

[bsutton]

I've re-opened this issue as its not quite working.

Whilst the triangle is now moved to the correct line it only gets re-displayed if you cause that area of the editor to re-draw.

I note that my CurrentStep ObservableValue class only ever gets InvalidationListeners added. I was expecting the CodeArea to add change listeners so that when I change the line number it would force a refresh of the old/new locations of the arrow indicataor.

I dug into the code of CodeArea but I really can work out what is going on. I thought looking at the code that updates the Carat position might provide some insight:

 @Override
    public void positionCaret(int pos) {
        try(Guard g = suspend(caretPosition, currentParagraph, caretColumn)) {
            internalCaretPosition.setValue(pos);
        }

But this code really didn't really help. I've got no idea what the suspend method does.

What do I need to do?

[TomasMikula]

Hi Brett,

first of all, you don't need a special CurrentStep class. Just define currentStep like this:

Property<Integer> currentStep = new SimpleObjectProperty<>(0);

If that doesn't solve your problem, please try to provide a simple self-contained example that I can help troubleshoot.

[TomasMikula]

Please, reopen with a SSCCE if the problem still persists.