fix(drag-drop): fix drag start delay behavior to allow scrolling (#16224)

[Aboisier]

I tried fixing the scrolling issue on mobile devices with my previous PR (#16228), but it did not work on iOS. There was also a bug with scrolling after the item has been dragged once. The native drag interactions were not toggled when the drag sequence is ended­.

In order to fix the iOS issue, we prevent default behaviour of pointer events fired after
the drag sequence has been started instead of only initialized.

[Aboisier]

Actually it seems like there is an issue with my solution. Sometimes, when you drag, it scrolls.

[trampi]

@Aboisier, @crisbesto: at the moment, scrolling is not possible on iOS devices if cdkDragDelay is set and the touch starts on an element with cdkDrag. This is IMHO a real problem, as screen-filling drag items now prevent the user from using the page, as they can not scroll. Not setting cdkDragDelay is obviously not really a fix.

@Aboisier: Whats the state of this PR? Can I help you somehow? Are you still working on fixing the drag scroll behavior you mentioned in your last comment?

Edit: for everyone else: use a DragHandle to work around this problem!

[Aboisier]

Hey @trampi , I don't think I will work on this PR in the near future. It seems like a change has been introduced between 8.0.2 and 8.1.0 and it's breaking my fix, so we are currently using a fork of 8.0.2 on which we applied #16228 and this PR. It's kind of stableish.

You're welcome to continue the work on this PR!

[trampi]

Hi @Aboisier, I would love to but I lack the time, experience and knowledge about CDK. Thank you for your feedback!

[plchampigny]

@crisbeto Can this fix be finished in order to fix this issue #17923

[mmalerba]

Closing since the relevant issue (#17923) has already been fixed

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