[Idle-dev] KeyConfig, KeyBinding and other related issues.

Terry Reedy tjreedy at udel.edu
Fri Jun 13 18:58:37 CEST 2014

On 6/13/2014 11:44 AM, Saimadhav Heblikar wrote:

> I would like the keyseq validator to be reviewed.

I will let Tal take first whack at the code.
> The diff file: https://gist.github.com/sahutd/0a471db8138383fd73b2#file-test-keyseq-diff
> A sample test runner file:
> https://gist.github.com/sahutd/0a471db8138383fd73b2#file-test-keyseq-runner-py

Incomplete patches can be posted to the tracker, where Rietveld can be 
used for review. Create a separate issue for 'Tk key-combination 
validator.' Make it a dependency of the test_combination and key-entry 
issues. If a function looks useful outside of Idle, we can propose 
adding it to tkinter.

> In its current form, it supports/has
>      modifiers = ['Shift', 'Control', 'Alt', 'Meta']
>      alpha_uppercase = ['A']
>      alpha_lowercase = ['a']
>      direction = ['Up',]
>      direction_key = ['Key-Up']
> It supports validating combinations upto 4 in length.
> Please test for the above set only. (It will extended easily to fully
> represent the respective complete sets. The reason it cant be done
> *now* is the due to how RE optionals are coded differently in my
> patch. See CLEANUP below). I will also add remaining keys like
> Backspace, Slash etc tomorrow.
> # Cleanup:
> If we decide to go ahead with RE validating keys as in the above patch,
> 0. I made the mistake of not coding RE optionals -> ((pat)|(pat)) same
> for all sets. The result is that, extending the current key set is not
> possible without making all RE optional patterns similar.(Read the
> starting lines of is_valid_keyseq method).
> 1. There is a lot of places where refactoring can be done and
> appropriate comment added.
> 2. I left the asserts as-is. They can be used in testing the validator
> method itself.
> 3. The above patch still needs support for Backspace, slash etc to be
> added. I decided to add, once I am sure we will use it.
> 4. I would like to know how it will affect Mac? What are system
> specific differences? Please run the test-runner script on it and do
> let me know.
> ---
> My friend told that this thing can be done by "defining a grammar and
> automata." I did read up about it, but found it hard to grasp
> everything. Can you say whether it would be easier to solve it that
> way than RE?

A regex (in the original form, without latter additions) defines a 
regular grammar and gets translated to an automaton automatically. The 
later additions make the languages parsed somewhere between regular 
languages and context-free languages. The translated automata are more 
complicated than the originals.  So, if something can sensibly be done 
with regex, and not something simpler, there unlikely to be any 
advantage to writing the automaton by hand.

Does the Tk manual (at Active state, for instance) anywhere defined the 
key-combination language that .bind() accepts?  If not, we might have to 
settle for a function with three possible answers: definitely ok, 
unsure, and definitely not ok (mispelling such as 'Atl', suffix after 
the key such as 'Key-a-Shift', repeated modifiers such as 
'Alt-Alt-Key-x' (even if Tk would allow that), missing key such as 

Terry Jan Reedy

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