Add more of OS X's native Emacs keybindings

[nopdotcom]

OS X supports many simple Emacs keybindings in native text fields. (It can do this because the system UI uses Cmd instead of Ctrl as its main modifier key.) Add bindings to functions which already exist in
DefaultEditorKit.

I have a Ctrl-k (cut to end of line) implementation, but it is an additional static RecordableTextAction class. I have not included it.

[cmaglie]

Interesting, never know that, are those key-bindings standard in OSX?

[cmaglie]

@ArduinoBot build this please

[cmaglie]

The 'cut' actions that here is set as Ctrl-W seems to be Ctrl-K instead.
From various sources I see that the mnemonics are:

Ctrl-K -> Kill (cut)
Ctrl-Y -> Yank (paste)

is that right?
All the other shortcuts works as expected.

[cmaglie]

ok after commenting here https://github.com/arduino/Arduino/pull/4743/files#r57473913 I re-read the OP comment:

I have a Ctrl-k (cut to end of line) implementation, but it is an additional static RecordableTextAction class. I have not included it.

and now I've all the pieces together: it seems that Ctrl-K works as "cut to the end of the line" if no text is selected, otherwise it works as a normal "cut".

@nopdotcom do you agree?

[nopdotcom]

tl;dr; Your described behavior is a good improvement; for example, Ctrl-K then Ctrl-Y should put the line back the way it was. The real Ctrl-K is complicated,

Long version: I hadn’t realized how complicated it actually is.

The native OS X behavior for Ctrl-K mimics Emacs very well, but it is confusing. There is a separate cut buffer used by OS X Ctrl-K and Ctrl-Y, unrelated to the clipboard.

Every action taken with Ctrl-K appends to the special buffer:

• If the cursor has moved since the last Ctrl-K, start with an empty special buffer.
• If there is a selection, append the selection into the special buffer, and delete the selection.
• If not at end of line, append the remainder of the line to the special buffer, and delete.
• If at end of line, add a newline to the special buffer, and delete the newline.

Ctrl-Y pastes the special buffer.

The end effect of this is that:

• Pressing Ctrl-K any number of times followed by Ctrl-Y is a no-op.
• From the start of line, Ctrl-K Ctrl-K cuts the whole line in a buffer, which you can then paste multiple times. In particular, Ctrl-A (beginning of line) Ctrl-K (cut line) Ctrl-K (cut newline) Ctrl-Y Ctrl-Y duplicates the current line.

These are wired into my fingers. But I would find it acceptable for Ctrl-A Ctrl-K Ctrl-Y RETURN C-y to duplicate the current line. Which would work with the mapping you described.

[nopdotcom]

Would you like me to clean up my Ctrl-K code and add it to this branch?

[cmaglie]

@nopdotcom
Yes, thank you!
If you can keep the implementation of CTRL-K / CTRL-Y on a separate commit I can start to cherry-pick the other shortcuts.

[cmaglie]

@nopdotcom I've merged your commit without the Ctrl+W and Ctrl+Y part, so we can move forward and close this PR.

02914d7
f74afc4

Feel free to open another PR when you have a correct implementation of the Kill/Yank feature!

Thank you!