stash

frontend/src/label.js

@@ -197,6 +197,18 @@ function relation(node, ownAxis, wantWidth, pxPerMm) {
     if (combinesAsWidth === wantWidth) {
         return {a, b};
     }
+    if (a === 0) {
+        // Every child is a fixed size (a === 0) in the combining direction - e.g. a row that's
+        // just one crisp QR leaf, with no scale-free (text) sibling to invert against. Inverting
+        // "width = b" for an a of 0 would divide by zero: a constant width genuinely doesn't
+        // determine a height, since nothing here actually scales with it. Ask each child directly
+        // for its own size in the wanted direction instead (every one of them must be similarly
+        // fixed, since only a fixed leaf ever contributes a === 0), and take the largest - the
+        // shared dimension has to fit whichever child needs the most room, with any child that
+        // ends up with room to spare centered within it (see drawQrLeaf).
+        const otherParts = node.map(child => relation(child, axis, wantWidth, pxPerMm));
+        return {a: 0, b: Math.max(...otherParts.map(p => p.b))};
+    }
     return {a: 1 / a, b: -b / a};				// invert: solve the affine relation the other way
 }