Adding GUI to already existing CLI framework

[Frank Aune]

Hello,

I'm about to begin designing a GUI for an already existing CLI framework 
written in python. And I believe its a good idea to invest some time into 
researching implementation ideas instead of jumping straight into writing 
code.

I do not want my CLI framework to be dependent on wx in any way, so the GUI 
must be completely separated.

All error messages in the CLI framework are handled by exceptions, so those 
are relatively easy to catch in the GUI. I have identified two areas where I 
must come up with a solution:

1. How to execute blocking code in the CLI framework from the GUI, without 
making the GUI unresponsive. 

2. How to signal messages and events from the CLI framework up into the GUI, 
without making the CLI framework dependent on the GUI. I'm thinking 
especially about progress bar updates and progress messages etc.


Possible solutions for 1. I can think of:
- Make decorator function in the GUI for threading the CLI framework
- Make CLI framework threaded
- Use twisted callbacks

Personally I dont like twisted callbacks in wx (never could make them work 
like I wanted), but I'm looking for advice on the cleanest way of 
accomplising this. I have used threads and thread-decorators in wx apps 
before, and I'm crazy enough to actually admit I like it :-)


Possible solutions for 2. I can think of:
- Let CLI framework communicate with GUI over a UNIX socket, possibly using 
JSON socket API.

- Use DBUS for signaling the GUI (the CLI framework deals with hotpluggable 
HW, so I think DBUS usage is a good idea anyway)

- Have a possible GUI object reference in the CLI framework constructor ( GUI 
= None), and then test if the GUI object exists - and if so, do signaling 
through the GUI object reference through a self-defined API. To separate the 
dependency on wx, I could make my own signaling layer which the CLI framework 
calls, and then in this layer again call wx functions.

- Just let the CLI framework send out wx.EVENTS and from CLI framework POW 
don't care if someone is listening. Then make the GUI respond to these 
events. This will make the framework depend on wx (at least it needs to 
import wx into its namespace and send out events), but perhaps this is an 
acceptable approach?

I'm pretty clueless on how to accomplish this in a clean way, so I am very 
much looking for good advice on how you guys deal with this sort of 
challenges!

Code examples, articles, tutorials, opinions - all are welcome :-)

Thank you very much for all input, and have a nice weekend!

Best regards,
Frank Aune