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
* <p>
     * This method must be called before any of the dialog unit based conversion
     * methods are called.
     * </p>
     * 
     * @param control
     *            a control from which to obtain the current font
     */
    protected void initializeDialogUnits(Control control) {
        
        GC gc = new GC(control);
        gc.setFont(JFaceResources.getDialogFont());
        fontMetrics = gc.getFontMetrics();
        gc.dispose();
    }
    /**
     * Notifies that the ok button of this dialog has been pressed.
     * <p>
     * The <code>Dialog</code> implementation of this framework method sets
     * this dialog's return code to <code>Window.OK</code> and closes the
     * dialog. Subclasses may override.
     * </p>
     */
    protected void okPressed() {
        setReturnCode(OK);
        close();
    }
    /**
     * Set the layout data of the button to a GridData with appropriate heights
     * and widths.