CrossLineStyleListener.java Source code

Introduction

Here is the source code for CrossLineStyleListener.java

Source

/*
Revised from The Definitive Guide to SWT and JFace
by Robert Harris and Rob Warner 
Apress 2004
*/

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.ExtendedModifyEvent;
import org.eclipse.swt.custom.ExtendedModifyListener;
import org.eclipse.swt.custom.LineStyleEvent;
import org.eclipse.swt.custom.LineStyleListener;
import org.eclipse.swt.custom.StyleRange;
import org.eclipse.swt.custom.StyledText;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class CrossLineStyleListener {
    public static void main(String[] args) {
        final Display display = new Display();
        final Shell shell = new Shell(display);

        final StyledText styledText = new StyledText(shell, SWT.V_SCROLL | SWT.BORDER);

        final MultiLineCommentListener lineStyleListener = new MultiLineCommentListener();
        styledText.addLineStyleListener(lineStyleListener);

        styledText.addExtendedModifyListener(new ExtendedModifyListener() {
            public void modifyText(ExtendedModifyEvent event) {
                // Recalculate the comments
                lineStyleListener.refreshMultilineComments(styledText.getText());
                // Redraw the text
                styledText.redraw();
            }
        });

        styledText.setBounds(10, 10, 500, 100);
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
    }
}

class MultiLineCommentListener implements LineStyleListener {
    // Markers for multiline comments
    private static final String COMMENT_START = "/*";
    private static final String COMMENT_END = "*/";

    // Color for comments
    private static final Color COMMENT_COLOR = Display.getCurrent().getSystemColor(SWT.COLOR_BLUE);

    List commentOffsets = new LinkedList();

    public void refreshMultilineComments(String text) {
        // Clear any stored offsets
        commentOffsets.clear();

        // Go through all the instances of COMMENT_START
        for (int pos = text.indexOf(COMMENT_START); pos > -1; pos = text.indexOf(COMMENT_START, pos)) {
            // offsets[0] holds the COMMENT_START offset
            // and COMMENT_END holds the ending offset
            int[] offsets = new int[2];
            offsets[0] = pos;

            // Find the corresponding end comment.
            pos = text.indexOf(COMMENT_END, pos);

            // If no corresponding end comment, use the end of the text
            offsets[1] = pos == -1 ? text.length() - 1 : pos + COMMENT_END.length() - 1;
            pos = offsets[1];

            // Add the offsets to the collection
            commentOffsets.add(offsets);
        }
    }

    /**
     * Called by StyledText to get the styles for a line
     *
     * @param event the event
     */
    public void lineGetStyle(LineStyleEvent event) {
        // Create a collection to hold the StyleRanges
        List styles = new ArrayList();

        // Store the length for convenience
        int length = event.lineText.length();

        for (int i = 0, n = commentOffsets.size(); i < n; i++) {
            int[] offsets = (int[]) commentOffsets.get(i);

            // If starting offset is past current line--quit
            if (offsets[0] > event.lineOffset + length)
                break;

            // Check if we're inside a multiline comment
            if (offsets[0] <= event.lineOffset + length && offsets[1] >= event.lineOffset) {
                // Calculate starting offset for StyleRange
                int start = Math.max(offsets[0], event.lineOffset);

                // Calculate length for style range
                int len = Math.min(offsets[1], event.lineOffset + length) - start + 1;

                // Add the style range
                styles.add(new StyleRange(start, len, COMMENT_COLOR, null));
            }
        }

        // Copy all the ranges into the event
        event.styles = (StyleRange[]) styles.toArray(new StyleRange[0]);
    }
}