pop-up blocker algorithm doesn't define behavior for touch

[RByers]

The allowed to show a pop-up definition lists a number of types of events, including mouseup and click. But doesn't define what the behavior should be for touch input, eg. inside of a touchend or pointerup listener.

Today chromium permits popup from within any touch event, but this has caused problems with pop-ups during a scroll. Safari appears to have a more complex algorithm where pop-ups can be opened from some touchend listeners (eg. corresponding to taps), but not others (eg. corresponding to scrolls). We're debating how we want to change the behavior in chromium here. Once we have data on what seems to work well, I'm happy to submit a PR to the spec for this.

If others have opinions on the constraints for this algorithm, please mention them here (or the above chromium bug).

[mikewest]

I'd love for @jeisinger to have time to look at this in more detail, as that algorithm is fairly naïve, and doesn't really match what browsers are doing. Touch events are only the tip of the iceberg.

[foolip]

Oh, so this is why scrolling the page is enough to clear the media playback restrictions in Blink :)

[jeisinger]

Anything you manage to come up with that reduces the number of scenarios where we instantiate an UGI that doesn't break all of the interwebs...

[domenic]

It looks like this got duplicated into #1358 and solved in #1875. The algorithm still has overall problems, which is tracked as #1903.