Overscroll & Pull to Refresh
in Chrome for Android
The overscroll glow effect on Android is triggered, per axis, under the following conditions:
Under such conditions, the unused, viewport-targeted scroll delta in the non-scrollable direction will be provided as an impulse to the edge glow effect. Note that content can prevent the overscroll effect from occurring by:
Pull-to-refresh in Chrome for Android (shipped in m41) augments the overscroll glow as one of the “default actions” for a touch sequence. The effect’s activation is slightly more restrictive in its initial conditions:
Transitioning from scrolling (or flinging) into overscroll continues to yield the overscroll glow, partially mitigating accidental refreshes. The refresh effect and action can be prevented by similar mechanisms noted for the overscroll glow effect, and is be purely cosmetic (not deforming or translating the content in any fashion). GMail’s pull-to-refresh provides a simple, cosmetic visual feedback model.
The default action of the pull-to-refresh effect can be effectively prevented by doing any of the following :
Note that the pull-to-refresh effect will never activate if any scrolling occurs before the overscrolling motion, e.g., if the user first scrolls down, then back up, or if the page scroll offset is 0 but has a scrolling div that the user scrolls up before overscrolling.
￫ See this simple page for an example of how to suppress the pull-to-refresh effect, including how to suppress pull-to-refresh but preserve the overscroll glow.
 This could be considered a bug, but some web devs use such a path explicitly to prevent the default top controls hiding behavior.
 This solution may change at some point in the future, but for the time being it also serves to disable omnibox hiding and some other default behaviors associated with body scrolling.
 Overscrolling touchmoves in this sense means touch events where 1) the page y scroll offset is zero, and 2) the touch event’s primary motion direction is downward (i.e., touch event coordinates are *increasing* and the user is logically overscrolling the page top).