Question

This is a question about which general approach to take, so I haven’t included any code.

Requirement:
I need to create a page within a multi-page editor that has two vertical sections in it. The top section has a tree and the bottom section has a text field. The tree and text field should fill their respective sections. Each section should scroll independently and there should be a splitter in between. When the editor is opened I want the visible area of the editor to be divided among the two sections based on some ratio I provide. Then when the editor is resized, the two sections will adjust proportionally to maintain the ratio and fit the page. This way there won’t be scroll bars on the editor page itself, just the two sections.

Proposed Solution:
My idea was to add a SashForm to the editor page and set the size of the SashForm to be the same as the editor’s visible area. Then I’d add a resize listener to the editor page and adjust the size of the SashForm so that it stays in sync with the page. However, I can’t find a way to get the editor’s visible area. So when I add the SashForm it just makes each section big enough to fit its data and adds a scroll on the editor page itself.

Is it possible to meet my requirement?

Answer 1

Success! The key was to listen for resize events on the ScrolledForm. I’ve only tested on Fedora but I’ll take a look on Windows soon. The only thing that bothers me is that the use of the buffer constants seems a little hacky.

/**
 * Form page that contains a sash form and a button.  The sash form is dynamically sized to ensure
 * that it always fills the available space on the page.
 */
public class SashFormDemoPage extends FormPage
{
    /** Horizontal buffer needed to ensure that content fits inside the page */
    private static final int HORIZONTAL_BUFFER = 8;
    /** Vertical buffer needed to ensure that content fits inside the page */
    private static final int VERTICAL_BUFFER = 12;

    /** Percentages of the sash form occupied by the tree and text box respectively */
    private static final int[] SASH_FORM_WEIGHTS = new int[] {30, 70};


    /**
     * Constructor
     * 
     * @param editor    parent editor
     */
    public SashFormDemoPage(ComponentEditor editor)
    {
        super(editor, "sashFormDemoPage", "Demo");
    }


    /**
     * {@inheritDoc}
     */
    @Override
    protected void createFormContent(IManagedForm managedForm)
    {
        // Set page title
        ScrolledForm scrolledForm = managedForm.getForm();
        scrolledForm.setText("SashForm Demo");

        // Set page layout and add a sash form
        final Composite parent = scrolledForm.getBody();
        parent.setLayout(new GridLayout());
        final SashForm sashForm = new SashForm(parent, SWT.VERTICAL);

        // Add a tree as the top row of the sash form and fill it with content
        FormToolkit toolkit = managedForm.getToolkit();
        int style = SWT.SINGLE | SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER;
        Tree tree = toolkit.createTree(sashForm, style);

        for (int i = 0; i < 40; i++) {
            TreeItem parentNode = new TreeItem(tree, SWT.NONE);
            parentNode.setText("parent-" + i);
            for (int j = 0; j < 3; j++) {
                TreeItem childNode = new TreeItem(parentNode, SWT.NONE);
                childNode.setText("child-" + i + "-" + j);
            }
        }

        // Add a text box as the bottom row of the sash form and fill it with content
        style = SWT.MULTI | SWT.V_SCROLL | SWT.WRAP | SWT.BORDER;
        Text text = toolkit.createText(sashForm, null, style);

        String message = "";
        for (int i = 0; i < 100; i++) {
            message += "This is a test of the layout demo system.  This is only a test.  ";
        }
        text.setText(message);

        // Add button below sash form
        final Button button = toolkit.createButton(parent, "Test", SWT.NONE);

        // Add resize listener to sash form's parent so that sash form always fills the page
        parent.addControlListener(new ControlListener() {
            @Override
            public void controlMoved(ControlEvent e)
            {
                // Stub needed to implement ControlListener
            }

            @Override
            public void controlResized(ControlEvent e)
            {
                GridData data = new GridData();
                Point size = parent.getSize();
                data.widthHint = size.x - HORIZONTAL_BUFFER;
                data.heightHint = size.y - button.getSize().y - VERTICAL_BUFFER;
                sashForm.setLayoutData(data);
            }
        });

        // Set sash form's weights and pack its parent so that the initial layout is correct
        sashForm.setWeights(SASH_FORM_WEIGHTS);
        parent.pack();
    }
}