texlabels

rpic extension. With texlabels = 1, any label string fully delimited as $…$ is typeset as inline TeX math — natively, by a pure-Rust engine (RaTeX, a KaTeX port). No LaTeX installation, no JavaScript, no fonts to install.

.PS
texlabels = 1; margin = 0.1
arrow "$u$" above
S: circle rad 10/72.27
line right 0.35
G: box "$G(s)$" wid 1 ht 0.55
arrow "$y$" above
line -> down G.ht from last arrow then left last arrow.c.x - S.x then to S.s
"$-\;$" below rjust
.PE

Coverage is KaTeX-grade — fractions, radicals, operators with limits, Greek, \mathbb, matrices:

.PS
texlabels = 1
box "$-\frac{T}{2}$" fit
move right 0.25
box "$\sqrt{2}\,V\sin(\omega t)$" fit
move right 0.25
box "$\displaystyle\sum_{n=1}^{\infty}\frac{1}{n^2}=\frac{\pi^2}{6}$" fit
.PE

Rules

• Off by default. With texlabels = 0, $…$ prints literally — exactly what dpic’s SVG mode does, so classic sources are untouched.
• Only strings fully delimited by $…$ (after trimming spaces) are typeset; anything else, including interior $, stays literal text.
• Metrics are exact (width, height, depth from the layout engine) — bboxes, anchors, fit and baseline alignment are more precise than the classic estimates.
• A formula that fails to parse falls back to the literal label plus a diagnostic; a bad formula never fails the picture.
• Activation can also come from the invocation, source staying sovereign: rpic -t, Python render_svg(src, texlabels=True), JS compile(src, { texlabels: true }).
• The default WASM build ships without the math engine (size budget) — labels fall back to literal there. The npm package additionally ships a math-enabled build: ready(undefined, { math: true }) lazy-loads it and $…$ labels typeset in the browser too (see Bindings).

The dpic ecosystem typesets labels through LaTeX in its TeX backends; texlabels brings that quality to rpic’s native SVG/PNG/PDF. Design and the full candidate study: docs/tex-labels.md.