U-shaped pedigree figure

[davmlaw]

There are enormous pedigrees, and you are limited by figure sizes for journals. One of the solutions is to bend the pedigree into a U/horseshoe shape - kind of looks like house of parliament seats.

Thomas says there is an example in a FAME paper - find/link it here

[davmlaw]

[davmlaw]

This is pretty hard.

First thing to do is constrain it so that this is only done in an export, ie not part of general layout, just a tick box on SVG/PDF export (render in U shape tickbox)

Remove "married in" people - ie just those with common ancestor remain (as graph above does) - this removes the complexity of horizontal joins etc

This will only ever look good on somewhat balanced graphs, that are very wide

Might be worth thinking about the invisible U shape that is where the nodes align upon.

The algorithm will be something like:

• For each generation, spread out along the midpoint of a line based on total descendants (to make room in subsequent generations) - in case of 1 (original founder) end up in middle
• Rotate nodes so that they are 90 degrees from the tangent
• Extend a bit up/down the generations across this rotation to make the visible line U shape

[davmlaw]

Got stuck, I think I will retry with a new prompt:

Implement the coordinate assignment for exportUShapeSvg in frontend/src/io/svg/uShapeExporter.ts using a parametric U-spine algorithm.

Context: The upstream code (in the same file) already correctly produces:

• bloodTree — a BFS tree of blood descendants with parent→children maps
• assignedInfo — a map from individual id → { generation: number, arm: "left"|"right"|"root", layoutX: number }
• Root couple left (male) and right (female) individuals

The invisible spine:
Define a U-shaped spine as the parametric path:

• Two straight vertical arms at x = leftStemX and x = rightStemX
• A semicircular (or smooth quadratic) curve connecting them at the bottom
• The spine is invisible — it is a coordinate reference, not a rendered element

Node placement rule:
Each generation maps to an arc distance along the spine measured from the bottom-centre. The further from the bottom, the more "outside" (toward the arm tips). -

• Generation 0 (founders, root couple): placed at the bottom of the spine (the curve midpoint)
• Generation G blood ancestors on arm A: placed ON the spine at arc position G × U_ROW_HEIGHT along arm A, measured upward from
  foundersY
• This makes each blood ancestor a literal point on the spine, not just an approximation

Child spread rule:
At each spine point, compute the local tangent direction. Children of the blood ancestor at that point spread perpendicularly to the tangent, centred at that same arc position but offset laterally:

• On a straight arm the tangent is vertical → perpendicular is horizontal → children spread horizontally outward from the backbone
  (left arm: children go left; right arm: children go right)
• On the curved portion the tangent rotates → children fan radially (this mainly affects the founders' couple line visual)

The spread width for a generation is proportional to the number of siblings: totalSpan = (n - 1) × U_CHILD_V_SPACING centred on the parent's spine position.

What this fixes:

Because children spread perpendicular to the tangent at the parent's arc position, the parent is at the spine while children sit at right angles to it. The parent is never "in the middle" of the children; the children are always in a column that is orthogonal to the backbone direction.

Rendering consequence:

• The backbone path traces through the spine arc positions of all blood ancestors (not just founders)
• The "descent line" between a gen-G ancestor and the branch point for their children is the spine segment between gen-G and gen-(G+1)
  arc positions
• The horizontal connector (on straight arms) runs from the spine to the children column at the children's arc position, not the
  parent's arc position
• The parent is visibly inside (lower on the spine arc) relative to the branch point

Keep from existing code:

• All functions above assignCoordinates
• renderUBackbone, renderRootCoupleLine, renderShape, renderDeceasedSlash, renderProbandArrow, seg, svgDefs, escapeXml
• The overall exportUShapeSvg structure

Replace entirely:

• assignCoordinates — new parametric placement
• renderArmClusterLines — connector from spine to children column must use the children's perpendicular direction and the children's arc position as the attachment y, not the parent's y
• The bounding box / offsetY calculation — derive from the spine geometry, not from Math.min(...allY), so arm nodes cannot pull the canvas top down and compress the visual separation

[davmlaw]

Tried, but could only get going for 2 levels deep in issue_2_export_u_shape branch