Re: Event mechanisms for GUI's

[tmoran@acm.org]

> There's nothing wrong with case statements. They're very clear and easy
In small quantity, yes.  But many-branched, nested, case statements with
a lot of near duplication are not so clear or maintainable.  They are
a very low abstraction level, computer-centric, device.
  If This_Window is for showing danger warnings in big red letters to the
reactor operator, and That_Window is for showing daily power demand over
the last month, a mouse click in either is similar from a computer-centric
view, but vastly different in the problem space.  Having This_Window_Type
objects and That_Window_Type objects as descendants of Basic_Window_Type
(inheriting what they have in common) makes them different objects, and a
dispatching call on When_Left_Button_Down(The_Clicked_Window) is in effect
a succinct abbreviation for a case statement on the type of Window,
implemented efficiently and without forgetfullness or typing errors,
automatically by the compiler.