Make entry editor DND behave as specified in settings

[Siedlerchr]

Fixes #5546

The setting only applies to the entry editor. The maintainable is still differentiating between the DND Modifiers as implemented in the linked PR
@koppor

Refs #3765

• 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• Check documentation status (Issue created for outdated help page at help.jabref.org?)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]

Difficult thing. I like the drag'n'drop preferences.

The best would be:

a) Respective icon is shown while dragging. (Think, that is impossible)
b) In case a modifier key is pressed (see the deleted comments: Alt, Ctrl, Shift), the OS-default action w.r.t. that key is taken. For instance, if I press Ctrl on Windows, the file os copied regardless of the FileDragDropPreferenceType.

Do you think, that's possible?

Oh, wait, it seems that the old code is close to that - but it does not work corretly for "no modifier" as the if statements there do not check for the OS.

[koppor]

Can we change this to a switch statement?

[Siedlerchr]

I actually found the old code confusing. If I select the default action to be linking and not moving, I would expect that behavior without pressing some modifier key.
However, if we decide to use modifier keys we should remove this setting from the preferences as the user gets the impression it is ignored. See the report in the linked issue.

My personal opinion would be to remove this modifier stuff at all. I doubt that the normal user is aware of the modifier keys

Checking for the OS does not make any sense, as it for linux depends on the desktop system the user has, and this might be different behaviors or not supporting modifiers

[koppor]

I checked #5546. There, it is only talked about WITHOUT modifier keys.

As professional Windows user, I use modifier keys, too. For me, it is OK, if modifiers worked on Windows only and had no effect on other operating systems.

Since no one else seems to know that one can press modifier keys while copying, we can let this in and in a follow-up issue discuss and implement a proper solution.

[tobiasdiez]

In my opinion, dnd onto the maintable and the entry editor should behave the same. Otherwise it's really confusing that some operations on the entry editor respect some settings while a similar action on the maintable does not.

[koppor]

Agree. Both should behave as outlined above (if possible) 😅 Tobias Diez <notifications@github.com> schrieb am Sa., 2. Nov. 2019, 15:01:

…

In my opinion, dnd onto the maintable and the entry editor should behave the same. Otherwise it's really confusing that some operations on the entry editor respect some settings while a similar action on the maintable does not. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#5554?email_source=notifications&email_token=AAKNU7TGK3HMYCTMNLVT7OLQRWB4BA5CNFSM4JH6CP4KYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEC44SFA#issuecomment-549046548>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAKNU7VFUZSIXUDQ7DLSVMTQRWB4BANCNFSM4JH6CP4A> .

[tobiasdiez]

@koppor why did you merged this although it removes functionality that we both agreed should be kept?! I'll revert since this is not a proper fix in my opinion.

[koppor]

I understood your comment wrong: I thought with this PR, they would behave the same. I did not check whether the entry editor supports modifier keys.

One should update JabRef#368 w.r.t. the current behavior of the entry editor.