Disable viewports inputs when dragging and dropping into the viewport

[ryevdokimov]

Fixes: #90112 and this comment #90112 (comment)

Having viewport inputs enabled while performing a drag and drop leads to issues especially in different navigation modes as mentioned in the linked issue. In theory the existing behavior sounds good, but in practice I believe it leads to more issues than it's worth. Usually, users put the target location in their viewport before dragging to it.

[ryevdokimov]

Just realized I haven't actually solved the problem, and it's a little bit more complex. Might have to look into disabling all input on the viewport before the data has even entered. I think this is more of an "input" problem, than simply not allowing certain functions depending on the drop data.

Edit: Yeah, I think that is probably the way to go, but correct me if I'm wrong.

[akien-mga]

Makes sense to me.

Edit: Not sure actually. I don't have a lot of hands on experience with 3D but it seems useful to me to be able to navigate the scene while dragging something to instantiate at a specific place. Sometimes the target is just a little bit off the current viewport, or zooming is needed to position things precisely, etc.

Actually, I'm not sure.

[ryevdokimov]

There is a precedent in other engines that handle this similarly to this PR. Like I said being able to navigate while you're dragging sounds good in theory, but now you're overlapping many functionalities that cause conflicts, even if it could work and we could find a way to separate it all out I think pressing that many button at once is kind of janky.

You already can't freelook/navigate in the viewport because of a few of these conflicts that exist in master. I think the workflow of finding your target first then dragging is pretty ingrained in most people that work with 3D a lot.

[KoBeWi]

it seems useful to me to be able to navigate the scene while dragging something to instantiate at a specific place

What are the options to navigate the scene though? Holding Alt rotates the camera, but only if you use non-Godot navigation scheme. I think most people use the default, which doesn't allow navigating while dragging (unless I'm missing some shortcut).

[akien-mga]

Alright, let's go with this approach and see if anyone complains their workflow broke.

[akien-mga]

Thanks!