When are non-blocking widgets useful?

Starting with IDL 5.0, users have the ability to run widget programs which do not block the IDL command line. This can be useful when using a command line approach to data visualization, but also require the use of a widget-based tool such as XLOADCT, XSURFACE, or a user-created widget program.

Discussion
For example, prior to IDL 5.0 starting XLOADCT from the command line forced the user to close the XLOADCT dialog before continuing with command line processing.

In IDL versions 5.0 and later, you can start the XLOADCT program and leave it running on your desktop while you continue to work at the IDL command line.

    IDL> WINDOW, 1
    IDL> SURFACE, DIST(40)
    IDL> XLOADCT
    IDL> SURFACE, DIST(40), AX = 20.0
    {Dismiss the XLOADCT program}

This flexibility gives you greater control over your visualization work by combining the power of widget-based tools with the convenience of the IDL command line.

To create a non-blocking user-created widget, simply set the NO_BLOCK keyword to each call to XMANAGER. For more information about creating non-blocking widgets, refer to the XMANAGER sections of the IDL documentation.