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the cost of interactive loveliness

You see, GUIs might look
Frank: What’s up now?
nice and easy, but they are
Joe: Well, it looks like I have to worry about lots of other GUI actually a pretty complicated
events, not just my own. beast under the hood. There‛s
lots of different events to
Jim: Yeah. It appears the operating system and this Window
Manager thing can give the GUI application work to do. worry about.
Frank: Yes, that’s right. All that interactive loveliness comes at a
cost.
Joe: Cost?!? You mean we have to pay?
Frank: No, not that sort of cost. You sometimes need to write a little
extra code to interact with the Window Manager when and where
necessary... that’s what I mean by “cost.”
Joe: Phew! So... what’s a Window Manager, anyway?
Frank: It’s something built into every GUI application that handles
the management of your application’s windows. Python’s GUI,
tkinter, has a Window Manager, as do all the other GUI toolkits.
Joe: So, how do I work with the events generated by the Window
Manager?
Frank: You create a function with the code you want to run and
then connect the function to the event.

Joe: OK, I get that. But which event do I connect up to? It’s not like
the Window Manager has a button to click on, is it?
Jim: That’s a good question... Frank?

Frank: Well spotted. What happens with the Window Manager is
that there’s a set of protocol properties that you can interact with as Joe Frank
and when required.
Joe: Protocol what? Properties? Jim
Jim: Yeah, you’ve lost me there, Frank.
Frank: Yes, protocol properties... they really are not as scary as they
sound. Remember: with GUIs, it’s all just code.
Jim & Joe: Where have we heard that before... ?
Frank: Here, let me show you what I mean...

320 Chapter 9