MessageFormat header/footerFormat how to change Font for JTable printing

Question

in relation to this thread I have a question if someone to know if is possible to override/change larger font (Font Type, Size, Color) for MessageFormat headerFormat comings with JTable.PrintMode or I must paint g2.drawString("my header/footer") and JTable#print() separatelly

Answer 1

As everybody already mentioned (while I was relaxing in vacation :-) - TablePrintable is tightly knitted for secrecy, no way to subclass, no way to configure the header/footer printing. The only option to hook is to wrap the table's default printable, let it do its work without header/footer and take over the header/footer printing oneself.

The problem with the snippets shown so far is that they dont play nicely with multi-page - as known and mentioned by all authors, of course - because the default printable thinks there are no headers/footers and freely uses the space required by them. Not surprisingly :-)

So the question is: is there a way to make to default not print into the region of the header/footer? And yeah, it is: double-wopper (ehh .. wrapper) is the answer - make the default printable believe it has less printable space by wrapping the given pageFormat into one that returns a adjusted getImageableHeight/Y. Something like:

public class CustomPageFormat extends PageFormat {

    private PageFormat delegate;
    private double headerHeight;
    private double footerHeight;

    public CustomPageFormat(PageFormat format, double headerHeight, double footerHeight) {
        this.delegate = format;
        this.headerHeight = headerHeight;
        this.footerHeight = footerHeight;
    }
    /** 
     * @inherited <p>
     */
    @Override
    public double getImageableY() {
        return delegate.getImageableY() + headerHeight;
    }

    /** 
     * @inherited <p>
     */
    @Override
    public double getImageableHeight() {
        return delegate.getImageableHeight() - headerHeight - footerHeight;
    }

    // all other methods simply delegate

Then use in the printable wrapper (footer has to be done similarly):

public class CustomTablePrintable implements Printable {

    Printable tablePrintable;
    JTable table;
    MessageFormat header; 
    MessageFormat footer;

    public CustomTablePrintable(MessageFormat header, MessageFormat footer) {
        this.header = header;
        this.footer = footer;
    }

    public void setTablePrintable(JTable table, Printable printable) {
        tablePrintable = printable;        
        this.table = table;
    }

    @Override
    public int print(Graphics graphics, PageFormat pageFormat, 
            int pageIndex) throws PrinterException {
        // grab an untainted graphics
        Graphics2D g2d = (Graphics2D)graphics.create();
        // calculate the offsets and wrap the pageFormat
        double headerOffset = calculateHeaderHeight(g2d, pageIndex);
        CustomPageFormat wrappingPageFormat = new CustomPageFormat(pageFormat, headerOffset, 0);
        // feed the wrapped pageFormat into the default printable
        int exists = tablePrintable.print(graphics, wrappingPageFormat, pageIndex);
        if (exists != PAGE_EXISTS) {
            g2d.dispose();
            return exists;
        }
        // translate the graphics to the start of the original pageFormat and draw header
        g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableY());
        printHeader(g2d, pageIndex, (int) pageFormat.getImageableWidth());
        g2d.dispose();

        return PAGE_EXISTS;        
    }


    protected double calculateHeaderHeight(Graphics2D g, int pageIndex) {
        if (header == null) return 0;
        Object[] pageNumber = new Object[]{new Integer(pageIndex + 1)};
        String text = header.format(pageNumber);
        Font headerFont = table.getFont().deriveFont(Font.BOLD, 18f);
        g.setFont(headerFont);
        Rectangle2D rect = g.getFontMetrics().getStringBounds(text, g);
        return rect.getHeight();
    }

    protected void printHeader(Graphics2D g, int pageIndex, int imgWidth) {
        Object[] pageNumber = new Object[]{new Integer(pageIndex + 1)};
        String text = header.format(pageNumber);
        Font headerFont = table.getFont().deriveFont(Font.BOLD, 18f);
        g.setFont(headerFont);
        Rectangle2D rect = g.getFontMetrics().getStringBounds(text, g);
        // following is c&p from TablePrintable printText
        int tx;

        // if the text is small enough to fit, center it
        if (rect.getWidth() < imgWidth) {
            tx = (int) ((imgWidth - rect.getWidth()) / 2);

            // otherwise, if the table is LTR, ensure the left side of
            // the text shows; the right can be clipped
        } else if (table.getComponentOrientation().isLeftToRight()) {
            tx = 0;

            // otherwise, ensure the right side of the text shows
        } else {
            tx = -(int) (Math.ceil(rect.getWidth()) - imgWidth);
        }

        int ty = (int) Math.ceil(Math.abs(rect.getY()));
        g.setColor(Color.BLACK);
        g.drawString(text, tx, ty);

    }
}

And at the end return that from table's getPrintable, like:

    final JTable table = new JTable(myModel){

        /** 
         * @inherited <p>
         */
        @Override
        public Printable getPrintable(PrintMode printMode,
                MessageFormat headerFormat, MessageFormat footerFormat) {
            Printable printable = super.getPrintable(printMode, null, null);
            CustomTablePrintable custom = new CustomTablePrintable(headerFormat, footerFormat);
            custom.setTablePrintable(this, printable);
            return custom;
        }

    };

printHeader/Footer can be implemented to do whatever is required.

At the end of the day: the answer to the question "do I need to call g.drawString(...)" still is "Yes". But at least it's safely outside of the table itself :-)