Re-displaying Subtools and Dialogs

The fragment of code below will create a new version of the tool every time it is called.

void create_a_subtool(void)
{
    tw_tool("Sub Tool", 256, 128);

    /** specify sub tool entries here **/

    tw_end_subtool();
}

Sub tools invoked by the user (say by a button press) are usually meant to be unique, and only need to be re-displayed if they have been iconified. They should thus be created with a code fragment like

void create_a_subtool(void)
{
    static void *tool_id = NULL;

    if(tool_id != 0)
    {
  tw_show_tool(tool_id);
  return;
    }

    tool_id = tw_tool("Sub Tool", 256, 128);

    /** specify sub tool entries here **/

    tw_end_subtool();
}

The first time the tool is invoked it will be created in the usual way, subsequent invocations will simply re-display the tool. Similarly dialog boxes should be created with a code fragment that allows them to be re-displayed after dismissal rather than re-created, e.g.

void create_a_dialog()
{
    static void *dialog_id = NULL;

    if(dialog_id != 0)
    {
  tw_show(dialog_id);
  return;
    }

    dialog_id = tw_dialog("Dialog Box");

    /** specify dialog entries here **/

    tw_end_dialog();
}