Fixes the hover flicker the maintainers' way (jacomyal/sigma.js#1493):
sigma v3 picks nodes by reading a single pixel from a picking
framebuffer rendered at HALF the CSS resolution, and has no setting
for hit padding. Small nodes get tiny, ragged hit edges, and our glow
halo (9px beyond the disc) was NOT pickable — moving the cursor from
the disc onto its own halo de-hovered it, an oscillation loop.
NodeCircleProgram subclass (registered via nodeProgramClasses)
replaces only VERTEX_SHADER_SOURCE: a verbatim copy of sigma 3.0.3's
circle vertex shader that adds PICKING_PAD_PX (10) of radius under
#ifdef PICKING_MODE alone. The visible pass never takes that branch,
so rendering is pixel-identical (verified headless); the pickable
disc is disc + 10px, covering the whole hover halo, so the halo is
now hoverable and small candidate nodes are comfortable to hit.
sigma/rendering is imported dynamically (its ESM build touches
WebGL globals at module scope; SSR-safe like the sigma import).
This replaces the reverted prototype-patch approach (f12480e).
sigma v4 ships this officially as the nodePickingPadding setting —
noted for a future upgrade.
amosblomqvist
8f5276040c