Juce might have an envelope editor component, but I have a long experience making such components for Unix and Windows and would like to build my own.
I didn’t see any tutorial that seems to be concerned with building a component that advanced, though.
Related question: does Juce do a Blit operation, copying an off-screen buffer onto the screen to allow flicker-free graphics? I’m not seeing that as a component method nor in the main class listing.