Third instance of the same pattern, and the worst ratio yet. Mantine mounts a HoverCard's
Popover machinery - Popover, PopoverTarget and PopoverDropdown - even when it is disabled.
A month grid is around 42 cells and `disabled` is `isEditMode || eventsForDate.length === 0`,
so on a typical month most days mounted three components for a card that can never open, and
in edit mode every single day did.
Measured on a real board: 42 Popovers, 42 PopoverDropdowns and 42 PopoverTargets - 126 of
this widget's 171 listener-attaching components - in a widget with only 251 DOM nodes. That
is a far worse components-per-node ratio than media-releases, which had 340 across 2,951
nodes.
Returning the day cell directly when disabled is behaviour-identical: a disabled HoverCard
never opens, so nothing observable is lost.
This is now the third place this exact Mantine behaviour has cost real work - after the
shared board context menu and the media-release tooltips. The general rule: Mantine overlay
components mount their full machinery regardless of `disabled`, so `disabled` is a
visual-suppression prop, not a cost-avoidance one. Deciding before rendering is what avoids
the cost.
Thomas Camlong
365b2ed13e