Also look at blog postings for more.
Gauge Widgets
These are some animated gauge widgets I did for an Upwork client. There are properties for color, range, animation speed, and other aspects. I also created custom widgets for Qt designer, so the client could drag and drop gauges on their product screen. I provided detailed instructions on how to build everything, and how to use the widgets in an overall design. All coded in C++, and tested on Linux and Windows.
A Complex Control GUI for a Laser Sub-system
This GUI controlled a sub-system of a large experimental laser system. It accesses an Oracle database, several cameras, and an actuator control system, in addition to system facilities.

The GUI provides for manual control of each actuator. The actuators are piezoelectric devices that effect change on a deformable mirror in a hexagonal pattern, hence the hexagonal elements.

LEDWidget
This widget was developed as part of a tutorial on creating custom Qt widgets that could be integrated into Designer.

Qt Signal Adapter Library
In 2011, I created the Qt Signal Adapter template library. It allows one to connect Qt signals to regular C++ function objects. Probably mostly obsolete, as newer versions of Qt provide the same functionality with several overloads of the connect method. There is learning value in the library, as it shows how to use the Qt meta object system to create slots and signals on the fly and invoke them dynamically.