[super_drag_and_drop] Dragging of Offscreen Items

[anlumo]

I've implemented a sliver-based scrollable grid view with a selection, and when dragging items all selected ones have to be dragged along, including the ones that are scrolled outside of the currently visible view.

It appears that super_drag_and_drop doesn't support this use case. Drag items have to be widgets, but offscreen items aren't part of the widget tree, and so there is no widget for them. I can provide another widget for the drag item via DragItemWidget's dragBuilder, but I'm running into problems there:

• If I don't add these widgets to the widget tree, no drag item is shown.
• If I add them in a way that they're permanently visible to the user (a stack view wrapping the grid view), it does work, but that's not what I want, since they're supposed to be scrolled offscreen and thus not visible to the user.
• If I wrap the DragItemWidgets with an Opacity(opacity: 0, ...) widget, the drag image also is invisible.
• If I wrap the DragItemWidgets with an Offstage widget, the drag image also is invisible.

I couldn't find a way to make this work, am I missing something?

[knopp]

If you have a specific use case like this you might want to look at the lower level BaseDraggableWidget, which lets you build the entire DragConfiguration independent of widgets.

[anlumo]

Thank you for the response! Unfortunately, the documentation for this class is rather lackluster, so it's taking a while to understand how to use it.