fix(block-ui): center PDF net labels

system-block-ui/src/rendering/export-pdf.ts

@@ -1,6 +1,7 @@
 import { jsPDF } from "jspdf";
 import { svg2pdf } from "svg2pdf.js";
 import { downloadBlob } from "./download-blob";
+import { normalizeTextBaselinesForSvg2Pdf } from "./normalize-text-baselines-for-svg2pdf";
 
 export { downloadBlob } from "./download-blob";
 
@@ -175,6 +176,7 @@ const prepareSheets = (input: SchematicPdfInput): PreparedSheet[] => {
       throw new TypeError(`Schematic sheet ${index + 1} has no SVG content`);
     }
     const element = parseSvg(sheet.svg);
+    normalizeTextBaselinesForSvg2Pdf(element.querySelectorAll("text, tspan"));
     const dimensions = getSvgDimensions(element);
     normalizeSvgViewport(element, dimensions);
     return { element };

system-block-ui/src/rendering/normalize-text-baselines-for-svg2pdf.test.ts

@@ -0,0 +1,61 @@
+import { describe, expect, test } from "bun:test";
+import { normalizeTextBaselinesForSvg2Pdf } from "./normalize-text-baselines-for-svg2pdf";
+
+const createBaselineElement = (
+  initialAttributes: Readonly<Record<string, string>>,
+) => {
+  const attributes = new Map(Object.entries(initialAttributes));
+
+  return {
+    attributes,
+    element: {
+      getAttribute: (name: string) => attributes.get(name) ?? null,
+      hasAttribute: (name: string) => attributes.has(name),
+      setAttribute: (name: string, attributeValue: string) => {
+        attributes.set(name, attributeValue);
+      },
+    },
+  };
+};
+
+describe("SVG text baseline compatibility", () => {
+  test("maps the dominant baseline and calibrates central text", () => {
+    const centered = createBaselineElement({
+      "dominant-baseline": "central",
+    });
+
+    normalizeTextBaselinesForSvg2Pdf([centered.element]);
+
+    expect(Object.fromEntries(centered.attributes)).toEqual({
+      "dominant-baseline": "central",
+      "alignment-baseline": "central",
+      dy: "0.08em",
+    });
+  });
+
+  test("preserves explicit alignment and positioning", () => {
+    const explicitlyAligned = createBaselineElement({
+      "dominant-baseline": "central",
+      "alignment-baseline": "hanging",
+    });
+    const explicitlyPositioned = createBaselineElement({
+      "dominant-baseline": "central",
+      dy: "0.2em",
+    });
+
+    normalizeTextBaselinesForSvg2Pdf([
+      explicitlyAligned.element,
+      explicitlyPositioned.element,
+    ]);
+
+    expect(Object.fromEntries(explicitlyAligned.attributes)).toEqual({
+      "dominant-baseline": "central",
+      "alignment-baseline": "hanging",
+    });
+    expect(Object.fromEntries(explicitlyPositioned.attributes)).toEqual({
+      "dominant-baseline": "central",
+      "alignment-baseline": "central",
+      dy: "0.2em",
+    });
+  });
+});

system-block-ui/src/rendering/normalize-text-baselines-for-svg2pdf.ts

@@ -0,0 +1,25 @@
+const SVG2PDF_CENTRAL_BASELINE_DY = "0.08em";
+
+type SvgTextBaselineElement = Pick<
+  Element,
+  "getAttribute" | "hasAttribute" | "setAttribute"
+>;
+
+export const normalizeTextBaselinesForSvg2Pdf = (
+  elements: Iterable<SvgTextBaselineElement>,
+): void => {
+  for (const element of elements) {
+    if (element.hasAttribute("alignment-baseline")) continue;
+
+    const dominantBaseline = element.getAttribute("dominant-baseline");
+    if (!dominantBaseline) continue;
+
+    element.setAttribute("alignment-baseline", dominantBaseline);
+
+    // jsPDF places its middle baseline slightly above the browser SVG
+    // central baseline. Preserve author positioning when compensating for it.
+    if (dominantBaseline === "central" && !element.hasAttribute("dy")) {
+      element.setAttribute("dy", SVG2PDF_CENTRAL_BASELINE_DY);
+    }
+  }
+};