App/app/api/po/[id]/export/route.ts

@@ -6,6 +6,7 @@ import { TC_FIXED_LINE, TC_DEFAULTS } from "@/lib/validations/po";
 import { downloadBuffer } from "@/lib/storage";
 import { CANCELLED_WATERMARK_PNG_BASE64, CANCELLED_WATERMARK_W, CANCELLED_WATERMARK_H } from "@/lib/cancelled-watermark";
 import { getImageSize, scaleToBox } from "@/lib/image-size";
+import { signatoryLayout } from "@/lib/po-export-layout";
 
 // ── Company fallback constants (used when no company is linked to a PO) ──────
 
@@ -476,27 +477,25 @@ export async function GET(request: NextRequest, { params }: Props) {
     };
 
     const sigExt = signatureBase64 ? scaleToBox(signatureSize ?? { width: 360, height: 96 }, 165, 44) : null;
-    const sigLeft = sigExt ? Math.round((SIG_BLOCK_PX - sigExt.width) / 2) : 0; // centred over the name
+    const stampExt = stampImg ? scaleToBox(stampImg, 80, 66) : null;
+    // Signature centred over the name; stamp to its RIGHT with a gap (no overlap).
+    const { sigLeft, stampLeft } = signatoryLayout({ blockPx: SIG_BLOCK_PX, sig: sigExt, stamp: stampExt });
 
-    // Stamp / seal — drawn FIRST so it sits BEHIND the signature, tucked to its right.
-    if (stampImg) {
-      const stampExt = scaleToBox(stampImg, 80, 66);
-      const stampLeft = sigExt
-        ? Math.min(SIG_BLOCK_PX - stampExt.width, sigLeft + sigExt.width - Math.round(stampExt.width * 0.35))
-        : SIG_BLOCK_PX - stampExt.width - 6;
+    // Stamp / seal — drawn FIRST so it layers BEHIND the signature if they ever touch.
+    if (stampImg && stampExt && stampLeft != null) {
       const stampId = wb.addImage({
         base64: stampImg.base64,
         extension: stampImg.mime === "image/jpeg" ? "jpeg" : "png",
       });
       ws.addImage(stampId, {
-        tl: anchorAt(Math.max(0, stampLeft), SIG_ROW - 1),
+        tl: anchorAt(stampLeft, SIG_ROW - 1),
         ext: stampExt,
         editAs: "oneCell",
       });
     }
 
     // Approver signature — drawn AFTER the stamp (on top), centred over the name.
-    if (signatureBase64 && sigExt) {
+    if (signatureBase64 && sigExt && sigLeft != null) {
       const imgType = signatureMime === "image/jpeg" ? "jpeg" : "png";
       const imgId = wb.addImage({ base64: signatureBase64, extension: imgType });
       ws.addImage(imgId, {

App/lib/po-export-layout.ts

@@ -0,0 +1,32 @@
+// Geometry for the exported PO's left signatory block (cols A-D).
+// The approver signature is centred over the name; the company stamp/seal sits to
+// its RIGHT with a gap so it never overlays the signature or name — important
+// because uploaded signatures/stamps aren't always transparent PNGs.
+
+export interface Size { width: number; height: number }
+
+export interface SignatoryLayout {
+  sigLeft: number | null;   // px from the block's left edge, or null when no signature
+  stampLeft: number | null; // px from the block's left edge, or null when no stamp
+}
+
+export function signatoryLayout(opts: {
+  blockPx: number;
+  sig: Size | null;
+  stamp: Size | null;
+  gap?: number;
+}): SignatoryLayout {
+  const gap = opts.gap ?? 10;
+  const sigLeft = opts.sig ? Math.round((opts.blockPx - opts.sig.width) / 2) : null; // centred
+
+  let stampLeft: number | null = null;
+  if (opts.stamp) {
+    stampLeft =
+      sigLeft != null && opts.sig
+        ? Math.min(opts.blockPx - opts.stamp.width, sigLeft + opts.sig.width + gap) // clear of the signature
+        : opts.blockPx - opts.stamp.width - 6; // no signature → right-align in the block
+    stampLeft = Math.max(0, stampLeft);
+  }
+
+  return { sigLeft, stampLeft };
+}

App/tests/unit/po-export-layout.test.ts

@@ -0,0 +1,39 @@
+import { describe, it, expect } from "vitest";
+import { signatoryLayout } from "@/lib/po-export-layout";
+
+const BLOCK = 503; // px width of the A-D signatory block
+
+describe("signatoryLayout", () => {
+  it("centres the signature in the block", () => {
+    const { sigLeft } = signatoryLayout({ blockPx: BLOCK, sig: { width: 153, height: 44 }, stamp: null });
+    expect(sigLeft).not.toBeNull();
+    expect(sigLeft! + 153 / 2).toBeCloseTo(BLOCK / 2, 0); // centre ≈ block centre
+  });
+
+  it("places the stamp to the RIGHT of the signature with no overlap", () => {
+    const sig = { width: 153, height: 44 };
+    const stamp = { width: 67, height: 66 };
+    const { sigLeft, stampLeft } = signatoryLayout({ blockPx: BLOCK, sig, stamp, gap: 10 });
+    expect(stampLeft! ).toBeGreaterThanOrEqual(sigLeft! + sig.width); // starts at/after signature ends
+    expect(stampLeft! + stamp.width).toBeLessThanOrEqual(BLOCK);     // stays inside the block
+  });
+
+  it("never overlaps even with the widest signature + stamp", () => {
+    const sig = { width: 165, height: 44 };   // scaleToBox caps
+    const stamp = { width: 80, height: 66 };   // scaleToBox caps
+    const { sigLeft, stampLeft } = signatoryLayout({ blockPx: BLOCK, sig, stamp });
+    expect(stampLeft!).toBeGreaterThanOrEqual(sigLeft! + sig.width);
+    expect(stampLeft! + stamp.width).toBeLessThanOrEqual(BLOCK);
+  });
+
+  it("right-aligns the stamp when there is no signature", () => {
+    const { sigLeft, stampLeft } = signatoryLayout({ blockPx: BLOCK, sig: null, stamp: { width: 67, height: 66 } });
+    expect(sigLeft).toBeNull();
+    expect(stampLeft! + 67).toBeLessThanOrEqual(BLOCK);
+    expect(stampLeft!).toBeGreaterThan(BLOCK / 2); // on the right side
+  });
+
+  it("returns nulls when there are no images", () => {
+    expect(signatoryLayout({ blockPx: BLOCK, sig: null, stamp: null })).toEqual({ sigLeft: null, stampLeft: null });
+  });
+});