898650 - Ensure CrossSlide direction is perpendicular to the container's scroll orientation

Status: RESOLVED FIXED

(Firefox for Metro Graveyard :: Firefox Start, defect)

Description

[Sam Foster [:sfoster] (he/him)]

According to the Windows styleguide, the cross-slide gesture should be on the opposite axis to the scroll axis. So, grids in horizontally oriented containers (i.e. you would pan or scroll side-side) should swipe up/down to select tiles. For a vertically oriented container, you should swipe side-side to select tiles. 

Currently, the tiles in snapped-view still cross-slide on the y-axis, so either the getScrollAxisFromElement implementation in CrossSlide.jsm is buggy, or there's an unexpected horizonal-oriented container in there producing the unexpected result.

Comment 1

[Sam Foster [:sfoster] (he/him)]

Blocks 8.1 support - the start UI and grids are not really scrollable or easily selectable because of scroll-axis errors.

Comment 2

[Sam Foster [:sfoster] (he/him)]

Attachment: Use document aspect ratio check to determine scroll direction

CrossSlide's getScrollDirection was trying to be accommodating of the possibility of an element being inside a scrollable div or something that might disagree with the document's own scroll direction. That's kind of an anti-pattern as far as Metro is concerned I think. Furthermore, the overflow CSS property checks weren't returning the right result in snapped view. I /think/ this new logic gets us the result we want - wide documents scroll left-right, tall documents top-bottom. We could also check scrollMaxX/Y. Or maybe there's a better method I'm missing? It seems like we must know the scroll direction already in order to handle panning, but I didn't spot it yet if so.

We only currently use CrossSlide in the start UI, but if its cheap/easy it would be good to keep it reusable elsewhere.

Comment 3

[Matt Brubeck (:mbrubeck)]

Comment on attachment 796380 [details] [diff] [review]
Use document aspect ratio check to determine scroll direction

Review of attachment 796380 [details] [diff] [review]:
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Looks good to me.

Comment 4

[Sam Foster [:sfoster] (he/him)]

Attachment: Simplified scroll direction heuristics using scrollMaX/Y then document aspect ratio

Added an early return when we have non-zero scrollMaxX or scrollMaxY. Tests out well for me using snapped, full, landscape and portrait, and should work for split view

Comment 5

[Sam Foster [:sfoster] (he/him)]

On fx-team: 
https://hg.mozilla.org/integration/fx-team/rev/1793358348cf

Comment 6

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/1793358348cf