From 1c812e88134940d5a6bca4a059a92528c8f16ecb Mon Sep 17 00:00:00 2001
From: John O'Keefe <jrokeefe@protonmail.com>
Date: Mon, 17 Aug 2026 08:40:03 -0400
Subject: [PATCH] Add recenter(): reset pan while keeping the current zoom

---
 fixed-layout.js | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/fixed-layout.js b/fixed-layout.js
index 767089a..716941d 100644
--- a/fixed-layout.js
+++ b/fixed-layout.js
@@ -193,6 +193,25 @@ export class FixedLayout extends HTMLElement {
     this.#render();
   }
 
+  // Reset pan while keeping the current zoom: the wrapper's base layout
+  // already centers the spread, so translate(0,0) recenters it. Re-syncs
+  // #side afterwards (same rule as drag-end) so next()/prev() stay sane.
+  recenter() {
+    this.#transform.x = 0;
+    this.#transform.y = 0;
+    this.#applyTransform();
+    if (
+      !this.#center &&
+      !this.#left?.blank &&
+      !this.#right?.blank &&
+      !this.#portrait
+    ) {
+      const leftWidth = (this.#left.width ?? 0) * this.#transform.scale;
+      const viewportCenterInWrapper = this.getBoundingClientRect().width / 2;
+      this.#side = viewportCenterInWrapper < leftWidth ? "left" : "right";
+    }
+  }
+
   toggleMagnifier() {
     this.#magnifier.enabled = !this.#magnifier.enabled;