Bug 80429 [Preferences] [Dialogs] FieldEditors should relax requirements to support DialogPages
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/FieldEditor.java
}
    /**
     * Clears the normal message from the message line.
     */
    protected void clearMessage() {
        if (page != null)
            page.setMessage(null);
    }
    /**
     * Returns the number of pixels corresponding to the
     * given number of horizontal dialog units.
     * <p>
     * Clients may call this framework method, but should not override it.
     * </p>
     *
     * @param control the control being sized
     * @param dlus the number of horizontal dialog units
     * @return the number of pixels
     */
    protected int convertHorizontalDLUsToPixels(Control control, int dlus) {
        GC gc = new GC(control);
        gc.setFont(control.getFont());
        int averageWidth = gc.getFontMetrics().getAverageCharWidth();
        gc.dispose();
        double horizontalDialogUnitSize = averageWidth * 0.25;
        return (int) Math.round(dlus * horizontalDialogUnitSize);
    }
    /**
     * Returns the number of pixels corresponding to the
     * given number of vertical dialog units.