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
defaultButton.moveBelow(null);
            }
        }
        super.initializeBounds();
    }
    /**
     * Returns true if the given Control is a direct or indirect child of
     * container.
     * @param container the potential parent
     * @param control
     * @return boolean <code>true</code> if control is a child
     *  of container
     */
    private boolean isContained(Control container, Control control) {
        Composite parent;
        while ((parent = control.getParent()) != null) {
            if (parent == container)
                return true;
            control = parent;
        }
        return false;
    }
    /**
     * The <code>Dialog</code> implementation of this <code>Window</code>
     * method creates and lays out the top level composite for the dialog, and
     * determines the appropriate horizontal and vertical dialog units based on
     * the font size. It then calls the <code>createDialogArea</code> and
     * <code>createButtonBar</code> methods to create the dialog area and
     * button bar, respectively. Overriding <code>createDialogArea</code> and
     * <code>createButtonBar</code> are recommended rather than overriding