Enabling scrolling for canvas SWT Draw2d

Question

I'm trying to display more on the canvas than is allowed by the window's/canvas's size limits. I know that there are a couple of ways to this. I could use the FigureCanvas but I'm unsure how the viewport ties into it. I opted to create a ScrolledComposite and placing a canvas within it. My problem is that the scroll bars appear but moving them makes no difference to what is shown on the canvas. Could anyone please point me in the right direction of fixing this? Thanks. *I've added short testable code illustrating the problem.

import org.eclipse.draw2d.ColorConstants;
import org.eclipse.draw2d.Figure;
import org.eclipse.draw2d.IFigure;
import org.eclipse.draw2d.LightweightSystem;
import org.eclipse.draw2d.SimpleRaisedBorder;
import org.eclipse.draw2d.geometry.Rectangle;
import org.eclipse.swt.widgets.Dialog;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.SWT;
import org.eclipse.wb.swt.SWTResourceManager;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.layout.GridData;
import org.xml.sax.SAXException;
import org.eclipse.swt.custom.ScrolledComposite;


public class ScrollDemo extends Dialog {

    protected Shell shell;
    protected IFigure panel;
    protected IFigure v_panel;

    public static void main(String[] args)
    {
        ScrollDemo act= new ScrollDemo(new Shell(), SWT.DIALOG_TRIM | SWT.APPLICATION_MODAL);
        act.open();
    }


    /**
     * Create the dialog.
     * @param parent
     * @param style
     */
    public ScrollDemo(Shell parent, int style) {
        super(parent, style);
        setText("Scrolling Demo");
    }

    /**
     * Open the dialog.
     * @throws SAXException 
     */
    public void open(){
            createContents();
        shell.open();
        shell.layout();
        Display display = getParent().getDisplay();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
    }

    /**
     * Create contents of the dialog.
     */
    private void createContents(){
        shell = new Shell(getParent(), getStyle());
        shell.setSize(475, 375);
        shell.setText(getText());
        shell.setLayout(new GridLayout(1, false));

        ScrolledComposite scrolledComposite = new ScrolledComposite(shell, SWT.BORDER | SWT.H_SCROLL | SWT.V_SCROLL);
        scrolledComposite.setBackground(SWTResourceManager.getColor(SWT.COLOR_DARK_MAGENTA));
        GridData gd_scrolledComposite = new GridData(SWT.LEFT, SWT.CENTER, false, false, 1, 1);
        gd_scrolledComposite.widthHint = 453;
        gd_scrolledComposite.heightHint = 245;
        scrolledComposite.setLayoutData(gd_scrolledComposite);
        scrolledComposite.setExpandHorizontal(true);
        scrolledComposite.setExpandVertical(true);

        Canvas canvas = new Canvas(scrolledComposite,  SWT.H_SCROLL | SWT.V_SCROLL);
        canvas.setBackground(SWTResourceManager.getColor(SWT.COLOR_DARK_YELLOW));
        scrolledComposite.setContent(canvas);
        scrolledComposite.setMinSize(canvas.computeSize(SWT.DEFAULT, SWT.DEFAULT));

        LightweightSystem lws = new LightweightSystem(canvas); 
        panel = new Figure(); 
        lws.setContents(panel);

        int starting_xpos= 0;
        int starting_ypos= 0;
        makeStructure(starting_xpos, starting_ypos, 0);


    }

    private void makeStructure(int starting_xpos, int starting_ypos, int index)
    {
        org.eclipse.draw2d.Label lblRoot= new org.eclipse.draw2d.Label();
        Rectangle rect= new Rectangle(starting_xpos, starting_ypos, 200, 25);
        //Anything longer than 200 cannot be displayed

        lblRoot.setText("BAAAAAAAAAAAB");

        lblRoot.setBorder(new SimpleRaisedBorder());
        lblRoot.setForegroundColor(ColorConstants.black);
        lblRoot.setVisible(true);
        lblRoot.setOpaque(true);
        lblRoot.setBounds(rect);

        panel.add(lblRoot);

         if (index<10)
            {
                makeStructure(starting_xpos+20, starting_ypos+50, index+1);
            }
        }


    }

score 2 · Accepted Answer · answered Jul 27 '14 at 13:36

Ok, I managed to get it working by using a FigureCanvas instead of a Canvas and by using a Viewport as the root element:

public class Draw2d extends Dialog
{
    protected Shell     shell;
    private Viewport    viewport;

    public static void main(String[] args)
    {
        Draw2d act = new Draw2d(new Shell(), SWT.DIALOG_TRIM | SWT.APPLICATION_MODAL);
        act.open();
    }

    public Draw2d(Shell parent, int style)
    {
        super(parent, style);
        setText("Draw2d");
    }

    public void open()
    {
        createContents();
        shell.open();
        shell.layout();
        Display display = getParent().getDisplay();
        while (!shell.isDisposed())
        {
            if (!display.readAndDispatch())
            {
                display.sleep();
            }
        }
    }

    private void createContents()
    {
        shell = new Shell(getParent(), getStyle());
        shell.setSize(475, 375);
        shell.setText(getText());
        shell.setLayout(new GridLayout(1, false));

        FigureCanvas canvas = new FigureCanvas(shell, SWT.H_SCROLL | SWT.V_SCROLL);
        canvas.setBackground(shell.getDisplay().getSystemColor(SWT.COLOR_DARK_YELLOW));
        canvas.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        canvas.setScrollBarVisibility(FigureCanvas.ALWAYS);
        viewport = new Viewport(true);
        canvas.setViewport(viewport);

        LightweightSystem lws = new LightweightSystem(canvas);
        lws.setContents(viewport);

        makeStructure(0, 0, 0);
    }

    private void makeStructure(int starting_xpos, int starting_ypos, int index)
    {
        org.eclipse.draw2d.Label lblRoot = new org.eclipse.draw2d.Label();
        Rectangle rect = new Rectangle(starting_xpos, starting_ypos, 210, 25);

        lblRoot.setText("BAAAAAAAAAAAB");

        lblRoot.setBorder(new SimpleRaisedBorder());
        lblRoot.setForegroundColor(ColorConstants.black);
        lblRoot.setVisible(true);
        lblRoot.setOpaque(true);
        lblRoot.setBounds(rect);

        viewport.add(lblRoot);

        if (index < 10)
        {
            makeStructure(starting_xpos + 20, starting_ypos + 50, index + 1);
        }
    }
}

Scrolling works just fine now.

Thank you very much. How do I increase the size of the canvas that can be accessed by scrolling? Changing the bounds of the canvas/ viewport did nothing for me. — Asher, Jul 28 '14 at 16:38
@Asher Do you need to increase it because you added new figures and they are out of the bounds or do you simply want to increase it? — Baz, Jul 28 '14 at 16:42
What do you mean out of the box? At present, it scrolls fine but only to a set width and height. How can I change those values? — Asher, Jul 28 '14 at 17:58
@Asher So when you add new figures, it does not adjust its bounds? — Baz, Jul 28 '14 at 18:41

Enabling scrolling for canvas SWT Draw2d

1 Answers1