[e-signature] Text overflow in signature box — drawCertInfo has no lower-bound clipping

[Yorizel]

Summary

drawCertInfo starts text at opts.y + opts.height - 20 and decrements by lineHeight = 14 per line with no check that text stays within the signature box. For small signature heights, text overflows below opts.y, placing content outside the designated signature rectangle.

Root Cause

appearance.ts:94:

let textY = opts.y + opts.height - 20;

And subsequent lines:

textY -= lineHeight;        // 14px per line
// ... no lower-bound guard

For height: 40, the box spans [opts.y, opts.y + 40]. Starting at opts.y + 20, then decrementing 14px × 4 lines = 56px total drop, text lands at opts.y - 36 — 36 points below the box floor.

Affected Files

• libraries/e-signature/src/appearance.ts:94 — textY initialization
• libraries/e-signature/src/appearance.ts:104-170 — no bounds check in the text-drawing loop

Evidence

For height: 60, up to 4 text lines are drawn:

Line 1: y = 60 - 20 = 40 above box origin      → inside ✓
Line 2: y = 40 - 14 = 26 above box origin      → inside ✓
Line 3: y = 26 - 14 = 12 above box origin      → inside ✓
Line 4: y = 12 - 14 = -2 above box origin      → OUTSIDE ✗

Suggested Fix

• Add a lower-bound guard before each page.drawText call:

  if (textY < opts.y) break; // or return — stop drawing outside box

• Or dynamically scale fontSize and lineHeight based on available box height
• Add a minimum height to schema (e.g., z.number().min(60)) to ensure the box can accommodate content