feat(board): detent horizontal board scroll to each column on mobile#51
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On a phone the columns hit their min-w-72 floor and the board scrolls sideways; a swipe used to rest anywhere, leaving two column halves on screen. Make the row scroll-snap x-mandatory with each column a snap-start point, so a horizontal swipe always settles with one column pinned to the left edge — each column becomes a "home" for the scroll. - snap-start (not center): a left-to-right board reads like flipping pages. - mandatory (not proximity): a firm home for every scroll, as asked. - No column-width change; snapping is purely additive. - Suppressed while a card is being dragged (gated on activeId): the drag edge auto-scroll scrolls this same row programmatically and mandatory snap fights it, stuttering the auto-scroll toward the target column. On drop, activeId clears and the row re-snaps to the nearest column. - No-op on desktop, where flex-1 fits every column and the row never overflows. Verified in WebKit at 390px: a partial nudge settled exactly on a column edge (0px delta) with zero page overflow. Documented in REFERENCE (board) and DECISIONS.
bryankennedy
approved these changes
Jul 4, 2026
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Why
On a phone the board columns hit their
min-w-72floor and the row scrolls sideways. A swipe used to rest anywhere, leaving you staring at two half-columns. This makes the horizontal scroll detent so each column is a "home" position.What
snap-x snap-mandatory; each column is asnap-startpoint → a swipe always settles with one column pinned to the left edge.activeId): the card-drag edge auto-scroll (PROG-47/48) scrolls this same row programmatically, and mandatory snap fights it — re-snapping after each step and stuttering the auto-scroll. On drop,activeIdclears and the row re-snaps to the nearest column.flex-1fits every column and the row never overflows.Testing
tsc -bclean. Verified in WebKit (Playwright) at a 390px iPhone viewport:scroll-snap-type: x mandatory, columns reportsnap-align: start, a partial nudge settled exactly on a column edge (0px delta), and zero page horizontal overflow.Docs
Updated
docs/REFERENCE.md(board section) and appended adocs/DECISIONS.mdentry covering the snap-start / mandatory / mid-drag-suppression choices.Design choices confirmed with the owner
Snap position left edge, column width unchanged (~288px floor), detent strength mandatory.