Keep engineering labels crisp

Compose scripts without baseline drift

schemd has no TeX runtime, and its labels still read like engineering notation. Grouped _ and ^ scripts nest. A bounded set of commands, such as \Omega, \pi, \theta, \mu and \infty, resolves to glyphs, and so do \langle, \rangle and \oplus. Hence |0\rangle reads as the ket it is. Each generated tspan carries an explicit baseline correction, so text that follows a nested script returns to the parent baseline and never drifts. Rotation stops at the vector. The label sits outside the rotated group and stays upright.

source:V7 "V_{ref}^{+}" at (100, 150) #blue [type=voltage-dc]
inductor:L7 "4.7 \mu H" at (330, 150) #purple [orientation=down]
qgate:Q7 "R_y" at (570, 150) #purple [parameter="\pi/3" phase="e^{i\theta}"]
port:O7 "\langle Z \rangle" at (800, 150) #emerald

Width is measured from a table and never from a browser, and no font is loaded at any point. The compiler carries the advance widths of Arial, which Helvetica, Liberation Sans and Arimo share, and it names that stack as the SVG's default font. Across the vocabulary the estimate is within 1.5% of the rendered width. Text is compressed with textLength only when it would overflow its space, and it is never stretched. A long label grows the component's bounds before placement is checked, which is why the whole scheme works without getBBox(), a call that server rendering cannot make. A page whose CSS sets a wider face on the SVG will see labels overrun the space measured for them.

A label may also be left out altogether. The part then draws its designator and no label row.

Use polished custom gate rows

qgate is the escape hatch, and it shares the exact shell of hadamard: the same stub lengths, corner radius, focus treatment and ports. Its parameter, phase and matrix rows grow the body by fixed amounts. A custom operator can therefore carry its own definition and remain the same kind of object.

prepare:PG "|0\rangle" at (80, 130) #blue
ry:RG "R_y" at (270, 130) #cyan [parameter="\pi/8"]
qgate:UG "V" at (480, 130) #purple [parameter="\theta" matrix="[a,b;c,d]"]
measure:MG "M_x" at (700, 130) #emerald

PG.out -> RG.in #blue [quantum line]
RG.out -> UG.in #cyan [quantum line]
UG.out -> MG.in #purple [quantum line]