Bug 33550 [Dialogs] Dialog should support remembering size and position
There are several dialogs that remember its size and position. Since restore the size and considering screen size and font changes isn't trivial JFace's Dialog class should support remembering and restoring size and position. These would realy ease the task for subclasses. May be you can steel the code from OpenTypeSelectionDialog.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
* layout.
     * </p>
     * <p>
     * Subclasses must override this method but may call <code>super</code> as
     * in the following example:
     * </p>
     * 
     * <pre>
     * Composite composite = (Composite) super.createDialogArea(parent);
     * //add controls to composite as necessary
     * return composite;
     * </pre>
     * 
     * @param parent
     *            the parent composite to contain the dialog area
     * @return the dialog area control
     */
    protected Control createDialogArea(Composite parent) {
        
        Composite composite = new Composite(parent, SWT.NONE);
        GridLayout layout = new GridLayout();
        layout.marginHeight = convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_MARGIN);
        layout.marginWidth = convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_MARGIN);
        layout.verticalSpacing = convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_SPACING);
        layout.horizontalSpacing = convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_SPACING);
        composite.setLayout(layout);
        composite.setLayoutData(new GridData(GridData.FILL_BOTH));
        applyDialogFont(composite);
        return composite;
    }