When I developed shortcuts customization tool I looked mostly on Qt Creator implementation. So:
- on gaining focus there is no replacing of current value (in Qt Creator), and keys are added at the end, but maybe replacing is really more convenient
- maximum length of 4 is because of QKeySequence max length of 4
- backspace button behavior is also came from Qt Creator, but they have "Reset" button as well, so maybe such change is good
- "reset to defaults" is already acting on both fields 

On Fri, Nov 2, 2012 at 6:54 PM, Bogdan Marinov <daggerstab@gmail.com> wrote:
Hello to all.

I have several issues with the current implementation of keyboard shortcuts customization (more on that later). I've already done some work on it trying to address them and fixing bugs.

I dislike the way shortcut editing works at the moment:
- on gaining focus, newly pressed keys are added to the end of the sequence. In all other similar GUI elements that I've seen, the current value is *replaced* after gaining focus.
- the "backspace" button is... strange. The symbol is the same one used in some desktop environments for "clear all the line edit's contents", and its positioning in most GUIs also suggests "clear all" or "reset to default". At the same time, the maximum possible length of a shortcut sequence is four combinations, so even in the worst case returning to replace a single combination doesn't save much more work than just clearing and re-entering the sequence.

What I'm going to do unless there are reasonable objections or counter-proposals:
- replace the "backspace" buttons with "clear" buttons
- add a "reset to defaults" button acting on both primary and alternate fields
- change the behavior, so the new combination is set while it's entered
- replace the "apply" button with "save settings"
- try to replace the static icon for the "backspace" buttons with text or a symbol (it's not night mode-d anyway)

I've been also working on adding a search/filter field, but there are some unexpected problems with it, so it may not appear yet.

Bogdan Marinov

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Best regards,
Anton Samoylov