Mobile webview taps on the chart doesn't display tooltips properly since vega version 5.26.0

[ZhaohuaZeng-at]

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Hi there, I think there is a bug introduced in 5.26.0 that makes tooltips not show up on tap on a mobile device.

I have reproduced this in CodeSandbox by simply swapping those two versions on the file.

To reproduce the issue, you can simply switch to mobile view on chrome browser via the developer tools, to simulate mobile taps. And then you can see that in 5.26.0 version of vega, tap on a bar in the bar chart doesn't display tooltip, and you have to keep on touching the bar to keep it on screen. However, in 5.25.0, once there is tap on a bar, the tooltip will keep on displaying.

Example videos:

in 5.25.0 (expected):

expected.mov

in 5.26.0 (bug):

bug.mov

[domoritz]

Is this related to #3781?

[kadamwhite]

Is this related to #3781?

@domoritz I believe so, yes. I've been looking into the pointer events, as you suggested in slack: this codepen shows the sequence of PointerOut and PointerMove events when you execute a tap and drag action. In my testing a pointerout event appears to fire immediately at the end of every PointerMove sequence, where mouseout by contrast would fire later on, or on a subsequent tap.

My guess is that this behavior is causing the tooltip to be hidden as soon as it is shown, which we can observe by viewing the mutations in the document element inspector: