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Issue or RFC Endorsed by Atom's Maintainers

Admittedly, this has not been endorsed by any maintainers (other than the fact that I'm submitting a PR for it now as a maintainer?).

Description of the Change

Previously, we would accept any drop request as valid in a drag-and-drop operation, regardless if we would actually do anything with it. Before signaling that a drop would be valid, we now check that 1) files are included in the drag store, and 2) the pane is in the workspace center.

The first check is entirely visual - this is to prevent the drop effect from changing to "move" instead of staying as "none" if the potential drop operation would be invalid.

The second check has an additional functional change - attempting to drop files onto docks no longer does anything. This is to prevent confusion, as TextEditors can only be opened in the center of the workspace, and I thought it was best to be explicit about that, even when initiating a drop operation. (Previously, dropping onto a dock would open the TextEditor in the workspace center, not the dock itself.)

Note: with this change, my drop effect on Windows is "copy" instead of "none" when the event is not prevented, and I can't figure out why. Maybe it's just a bug with Windows?
Edit: Maybe I need to look at 71a2797?

Alternate Designs

None.

Possible Drawbacks

You now must drop a file in the center workspace for a new TextEditor to be created.

Verification Process

• Dragging a file into the workspace center still opens a new TextEditor
• Dragging a file into a dock (e.g. the Git tab) does not do anything
• Dragging text into the workspace center does not do anything
• Dragging text into a dock does not do anything

Release Notes

N/A