Add copy and paste commands to terminal context menu

[krassowski]

References

Closes #3011

Re-uses the same interface to Clipboard API that we use in FileEditor's context menu for over two years now (#8425, JupyterLab 2.2).

Code changes

• add new methods to ITerminal interface: getSelection, hasSelection and paste following the underlying naming of xterjm.js implementation
• implement the new methods in Terminal by passing them over to xterm.js methods
• add new commands: terminal:paste and terminal:copy
• add the new commands to context menu

User-facing changes

• 'Refresh terminal' command now uses refresh icon when in context menu
• 'Copy' and 'Paste' context menu actions added

When pasting for the first time the browser may (depending on browser/settings) ask for confirmation to allow access to the clipboard:

All the caveats of this not working if browser restricts Clipboard API apply, see browser compatibility table.

For example, Firefox does not permit copy in non-secure contexts (https is ok) and does not allow paste at all. This is also the case for file editor, so this is not new. Ideally we would detect support and disable the command if support is not available but this is tricky for browsers which allow support after user consent.

Backwards-incompatible changes

Adds new non-optional methods to the interface.

If would like to backport to 3.6 if time permits, making the new methods optional in backport (but required for 4.0).

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[fcollonval]

Thanks @krassowski

Do you have time to make the backport this week. I'll like to get a beta out this week for 3.6; so we can focus on 4.0.0?

[fcollonval]

@meeseeksdev please backport to 3.6.x

It will likely fail but that will set the bot label

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout 3.6.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 43f4428916cbc3a83f9faa05091cd2bee523cd1c

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #13535: Add copy and paste commands to terminal context menu'

4. Push to a named branch:

git push YOURFORK 3.6.x:auto-backport-of-pr-13535-on-3.6.x

5. Create a PR against branch 3.6.x, I would have named this PR:

"Backport PR #13535 on branch 3.6.x (Add copy and paste commands to terminal context menu)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.

[dhirschfeld]

For example, Firefox does not permit copy in non-secure contexts (https is ok) and does not allow paste at all. This is also the case for file editor, so this is not new. Ideally we would detect support and disable the command if support is not available but this is tricky for browsers which allow support after user consent.

Thanks for the heads-up. No paste is a bit disappointing 😢 From the link you posted it seems you also need to opt-in to the read feature on Firefox: