Support a pan min offset / distance

Subject of the issue

I’d like to be able to configure an offset or distance within which a pan doesn’t start. Typically when dragging there is a margin of error to distinguish between a press (with wiggle) and a drag which tends to be implemented as a minimum distance a drag must move before recognising the event as a drag instead of a blurry press.

Your environment

• Version of panzoom: 4.0
• Browser and browser version: Google Chrome | 79.0.3945.117 (Official Build) (64-bit) (cohort: Stable)

Expected behaviour

1. Configure panzoom with an option like minPanDistance: 5
2. When panning, don’t start the pan action until the mouse/pointer has moved by 5 pixels
3. After the 5px threshold distance has been passed continue the pan as if the threshold didn’t exist - i.e. if the distance is 6px then the pan should be 6px and not 1px (6px - 5px)

Actual behaviour

No option exists, the pan begins immediately. This can cause UX issue when clicking or tapping on buttons/elements that are within the pan area as they can move unintentionally.

Steps to reproduce

This is a new feature, it can always be reproduced.

[mattnathan]

@timmywil I forked and applied the change I needed. I’ve created a PR which works for my application, whether it’s the correct way to do it for this project I don’t know. Hopefully it’ll help get the feature landed here anyway.

[timmywil]

Sorry I didn’t get back right away. There’s not really a set time on how long a feature can be collecting interest. That said, while this feature only has 2 votes, it has the most of the 3 features in the list so far. I’m not opposed to doing it, but I probably won’t have time in the near future. If you want to fork and fix, that could be the start of a PR! 😃