PointerXY and Tap yield different coordinates

HoloViews
1

I’m trying to use two crosshairs, one with PointerXY and one with Tap and it seems that they produce different coordinates for the same mouse position.

I’m noticing that there is a slight offset between these two. This offset can be visually seen by clicking then zooming in. Further, I have some callbacks attached to these that will extract information from a dataset at the hovered and clicked points. My expectation is that up clicking, the extracted information will be for the same point as the hover point, but that is proving not to be the case and PointerXY and Tap are yield different coordinates for the same mouse position.

I’m curious if anyone has any ideas on how to correct this behavior?

import geoviews as gv
import holoviews as hv

tiles = gv.tile_sources.OSM()

xlim = -20037508.34, 20037508.34
ylim = -20048966.1, 20048966.1
x0 = float((xlim[0] + xlim[-1]) / 2)
y0 = float((ylim[0] + ylim[-1]) / 2)

posxy = hv.streams.PointerXY(source=tiles, x=x0, y=y0)
clickxy = hv.streams.Tap(source=tiles, x=x0, y=y0).rename(x="x_click", y="y_click")  # type: ignore

def posxy_crosshair(x, y):
    kwargs = dict(color='red', line_width=1, line_dash="dashed")
    return hv.HLine(y).opts(**kwargs) * hv.VLine(x).opts(**kwargs)
posch = hv.DynamicMap(posxy_crosshair, streams=[posxy])

def clickxy_crosshair(x_click, y_click):
    kwargs = dict(color='black', line_width=1)
    return hv.HLine(y_click).opts(**kwargs) * hv.VLine(x_click).opts(**kwargs)
clch = hv.DynamicMap(clickxy_crosshair, streams=[clickxy])

(tiles * posch * clch).opts(active_tools=['wheel_zoom'], width=600, height=600).opts(xlim=xlim, ylim=ylim)

2

Hmm; that’s worrisome. There could be a good reason for this, but I’d suggest filing it as a bug report on github, because it sure doesn’t sound like how it should be behaving. At the very least if there’s such a difference deliberately, it should be documented clearly somewhere.

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