Java SWT show Line numbers for StyledText

Question

I was wondering if there is a straightforward way to display line numbers with StyledText text field - even if lines are wrapped. I'm using it in my application and if content gets to big, some line numbers would be nice.

Thank you.

Afrit

There's no true straightforward way as far as I'm aware; you could always put an uneditable text box to the left of your text editor. – Cerracchio

Check the implementation the Eclipse guys are using. – Vibrio

@Adam They are using a SourceViewer as shown here. I tried this example, but somehow I wasn't able to get it running properly. It was doing strange stuff on runtime. Anyway, I would like to keep my StyleText :) – Afrit

Answer 1

The key is org.eclipse.swt.custom.Bullet. It's basically a symbol (or in our case a number) you can add to the beginning of a line.

//text is your StyledText
text.addLineStyleListener(new LineStyleListener()
{
    public void lineGetStyle(LineStyleEvent e)
    {
        //Set the line number
        e.bulletIndex = text.getLineAtOffset(e.lineOffset);

        //Set the style, 12 pixles wide for each digit
        StyleRange style = new StyleRange();
        style.metrics = new GlyphMetrics(0, 0, Integer.toString(text.getLineCount()+1).length()*12);

        //Create and set the bullet
        e.bullet = new Bullet(ST.BULLET_NUMBER,style);
    }
});

Carraway

It works nice. It just misses to redraw all lines if the total amount of lines increases from 9 to 10. Or if a lines is removed in the middle of the file. Thank you. – Afrit

Answer 2

This is my working implementation.

styledText.addLineStyleListener(new LineStyleListener() {
    @Override
    public void lineGetStyle(LineStyleEvent event) {
        // Using ST.BULLET_NUMBER sometimes results in weird alignment.
        //event.bulletIndex = styledText.getLineAtOffset(event.lineOffset);
        StyleRange styleRange = new StyleRange();
        styleRange.foreground = Display.getCurrent().getSystemColor(SWT.COLOR_GRAY);
        int maxLine = styledText.getLineCount();
        int bulletLength = Integer.toString(maxLine).length();
        // Width of number character is half the height in monospaced font, add 1 character width for right padding.
        int bulletWidth = (bulletLength + 1) * styledText.getLineHeight() / 2;
        styleRange.metrics = new GlyphMetrics(0, 0, bulletWidth);
        event.bullet = new Bullet(ST.BULLET_TEXT, styleRange);
        // getLineAtOffset() returns a zero-based line index.
        int bulletLine = styledText.getLineAtOffset(event.lineOffset) + 1;
        event.bullet.text = String.format("%" + bulletLength + "s", bulletLine);
    }
});
styledText.addModifyListener(new ModifyListener() {
    @Override
    public void modifyText(ModifyEvent e) {
        // For line number redrawing.
        styledText.redraw();
    }
});

Note that the possible overhead of syntax highlighting recalculation when calling redraw() is likely to be acceptable, because lineGetStyle() are only called with lines currently on screen.

Infanticide

Answer 3

I believe that using a LineStyleListener should work. Something along the lines of:

styledText.addLineStyleListener(
    new LineStyleListener() {
        @Override
        public void lineGetStyle(LineStyleEvent event) {
            String line = event.lineText;
            int lineNumber = event.lineOffset;
            // Do stuff to add line numbers
        }
    }
);

Skerl

Could you please mention some more details about your approach? On the web, I just found a bunch of examples with LineStyleListener highlighting the content of a line in a certain way e.g. this example. Thank you. – Afrit

Answer 4

This is a way to use bullets that updates the numbers when the content changes:

text.addModifyListener(new ModifyListener() {
    public void modifyText(ModifyEvent event) {
        int maxLine = text.getLineCount();
        int lineCountWidth = Math.max(String.valueOf(maxLine).length(), 3);

        StyleRange style = new StyleRange();
        style.metrics = new GlyphMetrics(0, 0, lineCountWidth * 8 + 5);
        Bullet bullet = new Bullet(ST.BULLET_NUMBER, style);
        text.setLineBullet(0, text.getLineCount(), null);
        text.setLineBullet(0, text.getLineCount(), bullet);
    }
});

Ftlb

Answer 5

As a side-note for colouring the line numbers:

Device device = Display.getCurrent();
style.background = new Color(device, LINE_NUMBER_BG);
style.foreground = new Color(device, LINE_NUMBER_FG);

where LINE_NUMBER_BG and LINE_NUMBER_FG might be a RGB object such as:

final RGB LINE_NUMBER_BG = new RBG(160, 80, 0); // brown
final RGB LINE_NUMBER_FG = new RGB(255, 255, 255); // white

Logography