Add a way to create drag-and-drop source

[emilk]

I want something like window.is_dragged() to check if a window is being dragged.

The use-case I want to support is docking of window: I want to check if one winit window is being dragged onto another winit window, and if so collapse one into the other.

[kchibisov]

I don't think that's how it works? Maybe it's like that on macOS though, but I don't think it's how it's done in general.

if you're talking about firefox like tab dragging.

[kchibisov]

It usually works with the help of Drag and Drop and you get notified that you dropped a window into another window by that basically. You also need to create a drag with some handle identifying your window.

[emilk]

That's exactly what I'm talking about - detaching a tab into a new window, then drag it back to the original window again.

[kchibisov]

Yeah, you need drag and drop for that.

[emilk]

Thanks - I renamed the issue accordingly!

[kchibisov]

I'm impressed that we don't have issue to create drag and drop source.

[kchibisov]

Just in general, winit needs a way to create drag and drop sources, then you'll natively get a notification that you've dropped something into window Y, then by determining what you've dropped you perform an action.

Let's say you define that DND source is of mime type egui/surface and you pass some identifier as a part of DND operation. Then you use that ID to delete a window (if it was standalone) and put a content in a subview you have.

You can also use that to move view out of a window(creating a new window for it), etc.

[kchibisov]

The issue with all of that is that winit needs clipboard first, because DND sources are basically the same thing with a bit of extra as setting a custom surface along the drag and drop (you can draw a window preview there). But fundamentally it's the same things.