From c4619bb01dd929b29397afc7697958ca23c82c90 Mon Sep 17 00:00:00 2001
From: Derek Brooks <derek@broox.com>
Date: Thu, 2 Jan 2025 11:49:53 -0600
Subject: [PATCH] feat(zoom): Add ability to pan around an image on mouse move
 (#7831)

* Add ability to pan around an image by mouse to close #7306

* Make the zoom module's panWithMouse param more descriptive

* reuse onTouchMove event

---------

Co-authored-by: Vladimir Kharlampidi <nolimits4web@gmail.com>
---
 src/modules/zoom/zoom.mjs   | 69 +++++++++++++++++++++++++++++++++++++
 src/types/modules/zoom.d.ts |  6 ++++
 2 files changed, 75 insertions(+)

diff --git a/src/modules/zoom/zoom.mjs b/src/modules/zoom/zoom.mjs
index ba5860821..2279b5c92 100644
--- a/src/modules/zoom/zoom.mjs
+++ b/src/modules/zoom/zoom.mjs
@@ -14,6 +14,7 @@ export default function Zoom({ swiper, extendParams, on, emit }) {
       limitToOriginalSize: false,
       maxRatio: 3,
       minRatio: 1,
+      panOnMouseMove: false,
       toggle: true,
       containerClass: 'swiper-zoom-container',
       zoomedSlideClass: 'swiper-slide-zoomed',
@@ -26,6 +27,9 @@ export default function Zoom({ swiper, extendParams, on, emit }) {
 
   let currentScale = 1;
   let isScaling = false;
+  let isPanningWithMouse = false;
+  let mousePanStart = { x: 0, y: 0 };
+  const mousePanSensitivity = -3; // Negative to invert pan direction
   let fakeGestureTouched;
   let fakeGestureMoved;
   let preventZoomOut;
@@ -262,6 +266,9 @@ export default function Zoom({ swiper, extendParams, on, emit }) {
     image.touchesStart.y = event.pageY;
   }
   function onTouchMove(e) {
+    const isMouseEvent = e.pointerType === 'mouse';
+    const isMousePan = isMouseEvent && swiper.params.zoom.panOnMouseMove;
+
     if (!eventWithinSlide(e) || !eventWithinZoomContainer(e)) {
       return;
     }
@@ -270,8 +277,14 @@ export default function Zoom({ swiper, extendParams, on, emit }) {
       return;
     }
     if (!image.isTouched || !gesture.slideEl) {
+      if (isMousePan) onMouseMove(e);
+      return;
+    }
+    if (isMousePan) {
+      onMouseMove(e);
       return;
     }
+
     if (!image.isMoved) {
       image.width = gesture.imageEl.offsetWidth || gesture.imageEl.clientWidth;
       image.height = gesture.imageEl.offsetHeight || gesture.imageEl.clientHeight;
@@ -435,6 +448,53 @@ export default function Zoom({ swiper, extendParams, on, emit }) {
       gesture.originY = 0;
     }
   }
+  function onMouseMove(e) {
+    // Only pan if zoomed in and mouse panning is enabled
+    if (currentScale <= 1 || !gesture.imageWrapEl) return;
+    if (!eventWithinSlide(e) || !eventWithinZoomContainer(e)) return;
+
+    const currentTransform = window.getComputedStyle(gesture.imageWrapEl).transform;
+    const matrix = new window.DOMMatrix(currentTransform);
+
+    if (!isPanningWithMouse) {
+      isPanningWithMouse = true;
+      mousePanStart.x = e.clientX;
+      mousePanStart.y = e.clientY;
+
+      image.startX = matrix.e;
+      image.startY = matrix.f;
+      image.width = gesture.imageEl.offsetWidth || gesture.imageEl.clientWidth;
+      image.height = gesture.imageEl.offsetHeight || gesture.imageEl.clientHeight;
+
+      gesture.slideWidth = gesture.slideEl.offsetWidth;
+      gesture.slideHeight = gesture.slideEl.offsetHeight;
+      return;
+    }
+
+    const deltaX = (e.clientX - mousePanStart.x) * mousePanSensitivity;
+    const deltaY = (e.clientY - mousePanStart.y) * mousePanSensitivity;
+
+    const scaledWidth = image.width * currentScale;
+    const scaledHeight = image.height * currentScale;
+    const slideWidth = gesture.slideWidth;
+    const slideHeight = gesture.slideHeight;
+
+    const minX = Math.min(slideWidth / 2 - scaledWidth / 2, 0);
+    const maxX = -minX;
+    const minY = Math.min(slideHeight / 2 - scaledHeight / 2, 0);
+    const maxY = -minY;
+
+    const newX = Math.max(Math.min(image.startX + deltaX, maxX), minX);
+    const newY = Math.max(Math.min(image.startY + deltaY, maxY), minY);
+
+    gesture.imageWrapEl.style.transitionDuration = '0ms';
+    gesture.imageWrapEl.style.transform = `translate3d(${newX}px, ${newY}px, 0)`;
+
+    mousePanStart.x = e.clientX;
+    mousePanStart.y = e.clientY;
+    image.startX = newX;
+    image.startY = newY;
+  }
 
   function zoomIn(e) {
     const zoom = swiper.zoom;
@@ -598,6 +658,15 @@ export default function Zoom({ swiper, extendParams, on, emit }) {
     gesture.slideEl = undefined;
     gesture.originX = 0;
     gesture.originY = 0;
+
+    if (swiper.params.zoom.panOnMouseMove) {
+      mousePanStart = { x: 0, y: 0 };
+      if (isPanningWithMouse) {
+        isPanningWithMouse = false;
+        image.startX = 0;
+        image.startY = 0;
+      }
+    }
   }
 
   // Toggle Zoom
diff --git a/src/types/modules/zoom.d.ts b/src/types/modules/zoom.d.ts
index 658f5baef..f7b9dde44 100644
--- a/src/types/modules/zoom.d.ts
+++ b/src/types/modules/zoom.d.ts
@@ -63,6 +63,12 @@ export interface ZoomOptions {
    * @default 1
    */
   minRatio?: number;
+  /**
+   * When set to true, a zoomed in image will automatically pan while moving the mouse over the image
+   *
+   * @default false
+   */
+  panOnMouseMove?: boolean;
   /**
    * Enable/disable zoom-in by slide's double tap
    *