I know I’m a few years behind here, but for any future folks, this is the system I made and it is working flawlessly, but it involves a few steps.
I basically made a custom drag detector.
First, in the widget with the button, I override ‘Preview Mouse Button Down’ but return it unhandled so it doesn’t consume the input.
Then I send that input to a custom event and create a variable.
After that, I assign the ‘On Released’ dispatcher for the button to another custom event and call a custom event dispatcher with a reference to the widget with the button.
Continuing, when I populate the parent widget with the widget that contains the button, I assign my custom event dispatcher to yet another custom event (except in the parent widget).
On that custom event, I then check if a drag was detected (below). If a drag is not detected, then the code for the button clicked fires.
In the parent widget, I override ‘On Mouse Button Up’, again unhandled. I untick the first boolean and execute the previous custom event. Same as if I released the button.
Finally, on a tick event (I’m sending to another custom event), I first check if a drag was detected. The first execution of this should always be false since I’m setting it to true only if it is false. On false, I make sure the mouse button is down with the boolean I made earlier and then I check to see if the mouse moved vertically (this can be either or both) and if that’s true, a drag was detected. Now, the next tick, the first branch will be true. Now I can use the same delta input to offset the scroll box (or you can get the mouse position and ‘hold’ whatever your dragging). I have no need for the ‘OnDrop’ function/override, however you could use the false output of the mouse release event to ‘Release’ the dragged object (you would need to use a button and execute ‘OnHovered’ and send the widget reference to the parent to get where you want to drop it).
Here is a demonstration of the code (I don’t have app functionality yet but it would work, as I tested with a print string):
