TouchGFX: What Scenario(s) User Needs to Modify Generated FrontendApplication and FrontendHeap classes?

[BParh.1]

So I noticed the are two generated classes under user code section *gui folder), they are FrontendApplication class and FrontendHeap class. But so far I never really use them, I only modify ScreenView classes so far.

So what are these two Frontend*** classes? and what scenarios I need to modify them?