VSTTGUI4 is a mature and highly developed GUI API that includes advanced extensions called "Custom Views" and "Sub-Controllers" and this ASPiK SDK includes a sample project that demonstrates both of these concepts. This includes the use of some built-in C++ objects that implement the following:

• WaveView: a custom view that displays a waveform histogram
• SpectrumView: a custom view that displays a FFT (NOTE: you must install FFTW for this view to work)
• CustomKnobView: a custom view that subclasses the CAnimKnob object to show how to create and communicate with a view object
• KnobLinkController: a custom sub-controller that allows you to link CAnimKnob objects together so that moving one control moves the others in sync - linking knobs (e.g. for stereo operation) is a common necessity in some plugins.

The ASPiK examples will help you learn to design and use custom views and custom sub-controllers, allowing you to greatly extend the capabilities of your VSTGUI4 based UI.