Use distance threshold when suppressing click. about d3-drag HOT 4 CLOSED

I’m going to leave this open because I think it’s still a good enhancement to use a distance threshold for suppressing click.

from d3-drag.

as soon as the mousedown event fires, D3 starts listening to the mousemove.drag event, which immediately starts firing without any actual cursor move.

I’m going to be a tiny bit pedantic, but bear with me, as your point is taken.

Yes, d3-drag listens for a mousemove following mousedown, and interprets that as a non-empty drag gesture and thus cancels the subsequent click. But no, in general, a mousemove event does not follow a mousedown event unless the mouse also moved during the button press. Yet this behavior may be browser- or platform-specific, and is certainly device-specific: given a sensitive input device, pressing the mouse button is more likely to cause a small amount of mouse movement which then triggers mousemove events.

On the devices and platforms I primarily use (macOS), the current implementation works fine. But it is brittle in that any degree of mouse movement is interpreted as a non-empty drag gesture, and given the analog (or uncertain) nature of input, it would be more robust to have a distance threshold.

I’d compute the threshold based on the squared Euclidean distance, not that it makes much difference:

let d2;

drag.on('start', () => {
  d2 = 0;
});

drag.on('drag', () => {
  d2 += d3.event.dx * d3.event.dx + d3.event.dy * d3.event.dy;
});

drag.on('end', () => {
  if (d2 < clickTolerance) {
    d3.select(window).on('click.drag', null);
  }
});

Since you can have multiple active drag gestures, the d2 state here should be tracked on a per-gesture basis.

from d3-drag.

I have to confess I based my observations on one setup only (Mac OS X 10.11.6 and Google Chrome). For whatever reason I experienced constant mousemove event firing but I am unable to reproduce this. As long as I can't figure out what caused this weird behavior I assume this is no issue (or simply a technical issue on my end).

Sorry for taking up your time.

from d3-drag.

Fixed in 1.1.0.

from d3-drag.