The Driver's least favourite bug: on DX Life's research page a capability-4 plugin
with tabs at the top had a second, element-level scrollbar, and scrolling it scrolled
the TAB HEADER out of view.
doxa-maps-spa pins each fixed-viewport plugin with position:absolute;inset:0;height:
100% and its own comment states the invariant: "fills the pane exactly, so
scrollHeight===clientHeight and overflow:auto paints NO scrollbar." CSS never granted
that. A used height is CLAMPED between min-height and max-height, so a child's own
min-height BEATS the height:100% the shell sets -- it is a floor, not a preference.
Wherever the pane was shorter than that floor the pinned element grew taller than the
pane it was meant to fill, .dms-slot grew with it, and .dms-pane's overflow-y:auto
became a real scroll container wrapping the WHOLE plugin, tab strip included. That is
the second scrollbar: not the plugin's content scroller, the PANE scrolling the plugin
bodily. The invariant was written as a description and was only ever a hope.
The shell now pins with min-height:0. An inline style outranks a child's :host rule,
so that one property restores the invariant for every fixed-viewport plugin at once
without editing any of them. It is NOT added to the scroll-stack branch, where
natural height is the design.
A floor set INSIDE a child's shadow root is out of reach from the shell, and two of
mine had one. research-dashboard's .rd-shell and big-picture's .bp-root now say
min-height:inherit, deferring to :host -- which the gallery pins to 0, and which a
naive page leaves at its own floor, so the collapse guard those floors exist for is
kept rather than deleted. big-picture's 480px MOVED UP to :host rather than being
dropped: :host had no floor there, so inheriting would have quietly resolved to 0
everywhere and thrown away the black-screen guard its own comment calls load-bearing.
check-one-scroll-container asserts both halves, because either alone rots: the shell
still pins with min-height:0, and no plugin grows a NEW floor inside its shadow root.
The second half is what matters later -- a fixed shell plus a plugin that adds
min-height:700px next month is this bug again and nobody would connect it.
The rule is a CONTRADICTION IN ONE DECLARATION, not a large min-height by itself: an
element saying height:100% ("I fill whatever holds me") while refusing to be shorter
than N. My first version flagged any big min-height and caught gospel-resources'
.gd-map, a map deliberately sized height:80svh that scrolls inside its root's own
content scroller -- the one scrollbar a plugin is allowed. Flagging it would have sent
its owner after a non-bug, which is worse than not having the gate.
Negative-tested: removing min-height:0 from the shell, and reverting either .rd-shell
or .bp-root to a constant, each add a failure; restored, only the known one remains.
RED ON PURPOSE, and deliberately NOT in gates:pre. gospel-internet's .gb still carries
min-height:640px and that fix is its owner's. Wiring a red gate into gates:pre would
block the fleet on someone else's file, so the gates:pre entry belongs in the same
landing that fixes .gb -- until then this gate is the work item, afterwards the guard.
Source only: doxa-maps-spa, research-dashboard and big-picture need rebuilding, which
is the build owner's to do.
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