Question / Feature request: Expose onNodeDragStart or alternative to enable custom drag behaviors like spawning new nodes on drag

[klaraseitz]

Hi @vasturiano,

I’m currently working with Force Graph 2D and trying to implement a custom drag interaction where:

• When a user starts dragging a node, instead of moving the original node, a new node is created connected to the original,
• The drag then continues with this newly created node following the cursor,
• While the original node remains fixed in place.

Right now, the library provides onNodeDrag and onNodeDragEnd callbacks, but there’s no onNodeDragStart exposed.

I’m wondering if exposing onNodeDragStart would make it possible to implement this behavior? Or if there’s another way to programmatically transfer drag control to a different node mid-drag?

The main challenge is that the drag events are managed internally by d3-drag, and I couldn't find a way to intercept or reassign the dragging to a different node once started.
I plan to allow both drag types by implementing two distinct modes: one for moving existing nodes around, and another dedicated to adding nodes via drag.

Any advice, or plans to expose this event or add a way to control drag behavior would be greatly appreciated.

Thanks for the great library and for considering this!

[vasturiano]

@klaraseitz thanks for reaching out.

You should be able to easily detect the start of the drag using the current event handlers. Just set a flag on onNodeDrag and remove it on onNodeDragEnd. If you get a onNodeDrag without the flag set, you know it's the start of the drag.

Hopefully this mechanism allows to build the rest of your feature as you intend.

[klaraseitz]

@vasturiano thanks for you reply!
Maybe I haven't explained myself well. I didn't mean to be able to detect the start of a drag but rather initiate the start of a node.
Imagine also the use case where I drag a link. A link doesn't support dragging by default but if i could manually trigger the drag of a node I could have a similar behaviour. (in my use case i'd never need to drag both ends of a link, but always just the source would suffice.

Here is an example code snippet to show the initial dragging behaviour I tried to explain last time.
You can observe that dragging a node creates a new node in the same spot where dragging started. But the node that gets dragged is currently the old node. But i would like it to be the new node.

Is there any way to transfer the drag from one node to another? Or manually initiate the drag on the desired node?

Thanks! :)