Thanks to Ramsey Nasir from the LabVIEW team for this recap!
The "XControls in Theory and Practice" session was presented by Michael Porter from Lime Instruments. Mike is a Certified LabVIEW Architect and a LabVIEW Champion, so he has a lot of experience both developing in and talking about LabVIEW! He also happens to be a self-taught expert on XControl development.
XControls are customized LabVIEW controls that have VI code to support custom functionality. Mike discussed how XControls allow a LabVIEW developer to encapsulate control code and appearance for easy reuse. After describing the basic internal workings of XControls, Mike stressed that XControl code needs to be "able"- readable, scalable, and maintainable. It's good advice for writing software generally, but doubly important for XControls, which are both complicated and expected to be reused by other LabVIEW developers.
In addition to dispensing sage software engineering advice, Mike demonstrated several tricks for XControl developers, such as naming XControl properties so that they are nicely organized in property node popup menus and a way to store the XControl's internal state that completely avoids versioning issues. But possibly the biggest hit of the afternoon was his "probe VI" technique to easily see all of the important data inside an XControl without using breakpoints. Several attendees took photos of his block diagram so they could take it back to work with them to use in their own projects.