The virtual terminal (vterm)
                        ----------------------------

FINAL CUT uses a virtual terminal to print character via an update method
on the screen. It provides (as an overlying layer) virtual windows for
the realization of window movements. The update methods only transfer
differences to the virtual terminal or physical screen.



 print(...)
printf(...)
  │
  │          ╔════════════════════════[ vterm ]════════════════════════╗
  │          ║createVTerm()                                            ║
  │          ║                               ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ║
  │          ║                                                         ║
  │          ║                               │ restoreVTerm(x,y,w,h) │ ║
  │  ┌───────╨────[ vwin ]────────────┐                                ║
  │  │createArea(area)                │      └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ║
  │  │                                │                                ║
  │  │                                │                                ║
  └──┼────────►                  putArea(area) ────►                   ║
     │                                │                                ║
     │                         putArea(x,y,area) ────►                 ║
     │                                │                                ║
     │                   ◄──── getArea(x,y,area)                       ║
     │                                │                                ║
     │                                │                                ║
     │                                │                                ║
     │                resizeArea(area)│                                ║
     └───────╥────────────────────────┘                                ║
             ║                                                         ║
             ║       │                                    resizeVTerm()║
             ╚═══════▼═════════════════════════════════════════════════╝
                     │
                     │   putVTerm()
                     └──────────────────► updateTerminalLine(y)
                       updateTerminal()            │
                                                   ▼
                                           ┌───────────────┐
                                           │ output_buffer │
                                           └───────────────┘
                                                   │
                                                   │ flushOutputBuffer()
                                                   │ and putchar(char)
                                                   ▼
                                           ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄
                                           ▌               ▐
                                           ▌    screen     ▐
                                           ▌ ───────────── ▐
                                           ▌ real terminal ▐
                                           ▌               ▐
                                           ▀▀▀▀▀▀▀███▀▀▀▀▀▀▀
                                                  ███
                                               ▀▀▀▀▀▀▀▀▀