Add X11 Primary Selection clipboard support

[davidemdot]

Related to issue #2389 (JabRef and the X Window clipboard/selections).

I have been testing different alternatives and I think that this is the best choice (for using XClipboard a new dependency is needed, and it does not give any added value).

• All contents that JabRef sends to the system clipboard will be available in the X11 Primary clipboard too (i.e., copyVersionToClipboard() in the About dialog). So it is possible to paste it in a text editor, doing click in the middle/third mouse button.

• It is necessary to call the install() method in every text field where you want to use it. For the moment, it is activated in the GlobalSearchBar, therefore you can try it: write something, select a piece of text and do click in the middle button.

• Now ClipBoardManager uses the singleton pattern. It is instantiated once in Globals.java.

Any feedback will be more than welcome! :"D

---

• Change in CHANGELOG.md described
• Tests created for changes
• Manually tested changed features in running JabRef
• Screenshots added in PR description (for bigger UI changes)
• Ensured that the git commit message is a good one
• Check documentation status (Issue created for outdated help page at help.jabref.org?)

[koppor]

Thank you on working on this. No Linux at hand currently.

The primary and secondary buffers are completely separate buffers. So, the test case is:

1. Open JabRef
2. Add a new entry
3. Have the entry editor opened, showing the author and title field
4. Select Milton {Abramowitz} and Irene A. {Stegun} (here in this issue) and press Ctrl+C to copy that text to the primary buffer
5. Select Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables with the mouse. To not press any keyboard shortcut
6. Switch to JabRef (maybe using Alt+Tab)
7. Go to the title field.
8. Press the middle mouse key.
9. Check expectation: Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables is pasted.
10. Go to the author field.
11. Press Ctrl+V
12. Expectation: Milton {Abramowitz} and Irene A. {Stegun} appears.

@davidemdot Could you check if it works like that?

@gregoa This is the expected behavior if I remember the Linux desktop correctly. I checked https://docs.kde.org/trunk5/en/kde-workspace/klipper/clipboard-modes.html, which seems a good short resource on that. I see at https://ask.slashdot.org/story/04/06/02/1832201/dealing-with-the-unix-copy-and-paste-paradigm that Firefox pastes the secondary clipboard at Ctrl+V if text was selected in firefox.

Short summary for X11 clipboards: https://unix.stackexchange.com/a/139193/18033. Longer text (good introd pargraphs) : https://www.uninformativ.de/blog/postings/2017-04-02/0/POSTING-en.html. I learned, there is CLIPBOARD (typically Ctrl+C/V) and PRIMARY (mouse text highlight).

Source for the bibtex example: https://en.wikipedia.org/wiki/BibTeX

[davidemdot]

@koppor After last commit, which activates the PRIMARY clipboard for all TextField/TextArea controls in the entry editor, your test case works exactly as you said.

[koppor]

@gregoa @noMICROSOFTbuhtz Could you test if it meets your expectations? - Find the build at http://builds.jabref.org/issue-2389/.

[tobiasdiez]

Welcome back, it's been too long 😸

It's cool that's working now and the code looks good to me as well. I've only a few comments. I would also suggest that you propose these changes directly at the JavaFX upstream repository https://github.com/openjdk/jfx so that other could profit from the X11 support as well!

[koppor]

Minor comment remains.