Review the window event binding API

[tmontes]

Facts

• Currently mostly directly mapped to tkinter API.
• The bind_direct_key is the exception.
• Makes adapting to different backends non-trivial, probably.

Idea

• Simplify the API.
• Create a bind_key taking a "single letter" key argument:
  • Optional on_press=True, on_release=False arguments.
  • Optional direct boolean flag for the current bind_direct_key behaviour.
  • Will need to support non-letter keys, somehow (cursor keys, space, functions keys, backspace, etc).
  • Should support modifiers: shift, control, alt, command, meta, windows, etc.
• Create a a few mouse input focused methods: clicks, movement, scroll?
• Maybe a few Window related events: focus/unfocus/move/resize/minimize/restore/hide?

[tmontes]

Linking tk and Qt docs related to keyboard. These will be handy when looking for somewhat generic / common ground API solutions:

• tk bind - www.tcl.tk/man/tcl8.6/TkCmd/bind.htm
• Qt key enum - https://doc.qt.io/qt-5/qt.html#Key-enum
• Qt keyboard modifier enum - https://doc.qt.io/qt-5/qt.html#KeyboardModifier-enum