* QGraphicsScene similar Emacs' buffer, control content and state.
* QGraphicsView similar Emacs' window, control size and position.
* Every change in QGraphicsScene will synchronization to QGraphicsView in realtime by GPU composite.
* We use Xlib XReparent technology stick QGraphicsView to Emacs frame.
* Destroy QGraphicsView if emacs eaf-mode's window hide, create new QGraphicsView if eaf-mode window show, but QGraphicsScene still live in background until user kill eaf-mode buffer.
* When user use mouse click on QGraphicsView, QGraphicsView will translate mouse event coordinate and pass mouse event to QGraphicsScene to handle.
* When user use keyboard input in Emacs buffer, Emacs will key event to QGraphicsScene throught DBus IPC.
* Elisp call Python function through DBus method.
* Python call Elisp function through DBus signal.
## Why choose Qt?
Qt's QGraphicsView and QGraphicsScene is awesome, it's easier to implement window composite than other GUI library (such as GTK+).
