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RowHeightMixin

Auto-generated @jbrowse/mobx-state-tree API for the current JBrowse release — see pluggable elements for concepts. Built into JBrowse core. View source.

#crossCuttingMixin The two-valued row height every multi-row display has. A rowHeightConfigSchemaFields slot whose 0 means fit-to-display-height, and an autoRowHeight getter saying what that fit divides. Brings the raw rowHeight getter, setRowHeight, and the resolved effectiveRowHeight every consumer reads

The convention itself is agent-docs/reference/ROW_HEIGHT_AND_FIT.md; this is the middle link of it. Both ends were already shared: rowHeightMenuItem and SetRowHeightDialog in this directory are the one menu row and dialog for every row display, and resolveRowHeight in core is the one place the 0 sentinel resolves and a non-positive result is floored. What sat between them was three hand-written copies — maf, the multi-row feature painting and the multi-sample variant base — of the slot, the getter over it and the setter.

This package already depended on members it did not declare. rowHeightMenu restates rowHeight / setRowHeight / setFitToHeight as RowHeightModel and types.ts's TreeDrawingModel restates effectiveRowHeight, so a display wiring in the shared menu and spelling one of them differently compiled and then failed at the first click. Slots and accessors now move together, matching treeSidebarConfigSchemaFields + TreeSidebarMixin.

What stays per display is the value, not the declaration, and the doc says which: autoRowHeight, because the height available to rows is a different quantity in each (canvas's fitTargetHeight, maf's rowsHeight, variants' availableHeight), and setFitToHeight, because seeding the height slot on the way in is required exactly where the height getter is content-derived and wrong where it is the slot itself.

effectiveRowHeight is overridable, and one display overrides it: the multi-row feature painting caps the row stack at the canvas limit, since it sizes its canvas to its content instead of scrolling a viewport.

Getters

MemberDescription
rowHeight
number		Raw per-row height setting: 0 is fit-to-display-height, any positive value is a fixed px height. The resolved value is effectiveRowHeight — consumers read that, never this. On the config rather than the display snapshot for the same reason height is: the config node outlives the display instance, so a fixed height survives unticking and reticking the track.
autoRowHeight
number		The height fit mode divides between the rows, declared here and overridden by every display — the quantity differs in each, so this stub is a slot for the answer rather than an answer. Declaring it is what lets effectiveRowHeight below read a member of its own type instead of one asserted onto self.

A display that composes the mixin and supplies no override resolves to a 1px row, exactly as it did when this getter did not exist and the read found undefined: resolveRowHeight floors both.

Supply it as a getter, the way all three displays do. Mobx refuses to write a volatile over a computed, so a .volatile of this name throws at create — loudly, and before any row is drawn.
effectiveRowHeight
number		Resolved per-row height. rowHeight === 0 divides the display's own autoRowHeight across the rows; any positive value is the fixed px height, used as-is however many rows there are.

Sub-pixel is legitimate and deliberately not floored here — a cohort with more rows than the track has pixels has a genuinely fractional row height, and flooring it makes the content taller than the height it was asked to fit inside. resolveRowHeight floors only a non-positive result, which consumers divide by.

Actions

MemberDescription
setRowHeight
(n: number) => void		Pin a px row height. 0 is the fit sentinel, but enter fit mode through setFitToHeight instead — displays whose height getter is content-derived have to re-seed the slot on the way in, and that is what the action is for.