Use the newly proposed scroll-boundary-behavior for amp-sidebar, amp-lightbox

[aghassemi]

Proposed CSS standard scroll-boundary-behavior allows developers to decide the browser's behavior once a scroller has reached its full extent.

When launched, we should use it on amp-sidebar and amp-lightbox to prevent overscrolling of the parent body (using contain)

https://www.chromestatus.com/feature/5734614437986304
w3c/csswg-drafts#769
https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/txdySyr-mb0/tPQJZvJiBw
https://wicg.github.io/scroll-boundary-behavior/AJ

/cc @dvoytenko

[aghassemi]

/cc @cramforce: places we can use this in AMP

[cramforce]

CC @dvoytenko

[dvoytenko]

We should just do it.

[rudygalfi]

Rolling forward to H2 October milestone. Please correct if needed.

[cathyxz]

This is good in Chrome and Edge, but not implemented in Safari.

[dvoytenko]

@cathyxz Have we deployed this though?

[cathyxz]

Nope, sorry. I meant that the scroll-boundary-behavior attribute lives in Chrome, but not Safari in case we want to implement it.

[jridgewell]

Re: b/118645457. In the meantime, can we fix this behavior for scrollable lightbox? Something similar to the 1px scrollTop hack we do for iOS embed viewport.

[aghassemi]

@jridgewell We do that already https://github.com/ampproject/amphtml/blob/master/extensions/amp-lightbox/0.1/amp-lightbox.js#L482 b/118645457 happens regardless of scrollable lightbox.

[jridgewell]

You're only applying it in scrolling-up direction. You need to apply it to the scrolling-down direction, too.

[aghassemi]

@jridgewell Runtime doesn't do the bottom either

amphtml/src/service/viewport/viewport-binding-ios-embed-wrapper.js

Line 296 in 5e6b429

// Unfortunately, the same is very expensive to do on the bottom, due to

because it is expensive to do. Probably fine for lightbox though. I will give it a try

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.

[katsar0v]

Any update?