Copy/paste events

[tpoisseau]

#231 (comment)

How should we plan to implement copy/paste events.

On this PR I had to add some code in Java side, but the result was a bit hacky but use the clipboard events.

• skip ctrl+c/ctrl+v events
• a non-aware environment could trigger two same events (one from keyboard, another from clipboard events)

This implementation, which straddled the line between java and js, was unsatisfactory in my eyes.

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I think we should on https://github.com/Actelion/openchemlib define a generic API for clipboard, compatible with browser clipboard API and DataTransfer API.
It will be hard work, it will need to support async pattern (with callback, I think it will be the most simple we could do to be compatible with java and js)

With a generic clipboard api and clipboard events handling in java. The actual IClipboardHandler would need to change, but could have a single implementation in java, using an IClipboard.

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Or an other solution could be to do full implementation of copy-paste events handling in JS side for this repository, and do not propagate copy-paste events from keyboard to java.