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
buttonBar = null;
            dialogArea = null;
        }
        return returnValue;
    }
    /**
     * Applies the dialog font to all controls that currently have the default
     * font.
     * 
     * @param control
     *            the control to apply the font to. Font will also be applied to
     *            its children. If the control is <code>null</code> nothing
     *            happens.
     */
    public static void applyDialogFont(Control control) {
        if (control == null || dialogFontIsDefault())
            return;
        Font dialogFont = JFaceResources.getDialogFont();
        applyDialogFont(control, dialogFont);
    }
    /**
     * Sets the dialog font on the control and any of its children if thier font
     * is not otherwise set.
     * 
     * @param control
     *            the control to apply the font to. Font will also be applied to
     *            its children.
     * @param dialogFont
     *            the dialog font to set
     */