From 2e95244176f9f32ce8069cbce1599d39a1c1c922 Mon Sep 17 00:00:00 2001
From: Timmy Willison <4timmywil@gmail.com>
Date: Fri, 29 Oct 2021 16:22:41 -0400
Subject: [PATCH] fix(pan): avoid triggering the pan event if no change

Fixes gh-588
---
 src/panzoom.ts            | 12 +++++++-----
 test/unit/panzoom.test.ts | 34 ++++++++++++++++++++++++++++------
 2 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/src/panzoom.ts b/src/panzoom.ts
index be5cb4df..f98c48c5 100644
--- a/src/panzoom.ts
+++ b/src/panzoom.ts
@@ -291,12 +291,14 @@ function Panzoom(
     originalEvent?: PanzoomEventDetail['originalEvent']
   ) {
     const result = constrainXY(toX, toY, scale, panOptions)
-    const opts = result.opts
-
-    x = result.x
-    y = result.y
 
-    return setTransformWithEvent('panzoompan', opts, originalEvent)
+    // Only try to set if the result is somehow different
+    if (x !== result.x || y !== result.y) {
+      x = result.x
+      y = result.y
+      return setTransformWithEvent('panzoompan', result.opts, originalEvent)
+    }
+    return { x, y, scale, isSVG, originalEvent }
   }
 
   function zoom(
diff --git a/test/unit/panzoom.test.ts b/test/unit/panzoom.test.ts
index 8a1728b5..6382a07d 100644
--- a/test/unit/panzoom.test.ts
+++ b/test/unit/panzoom.test.ts
@@ -281,25 +281,38 @@ describe('Panzoom', () => {
       })
     })
   })
-  describe('force option', () => {
-    it('ignores disablePan', () => {
+  describe('disable options', () => {
+    it('disablePan', async () => {
       const div = document.createElement('div')
       document.body.appendChild(div)
-      const panzoom = Panzoom(div)
-      panzoom.setOptions({
+      const panzoom = Panzoom(div, {
         disablePan: true
       })
+      const badPanListener = () => {
+        assert.ok(false, 'panzoompan event should not be triggered')
+      }
+      ;(div as any).addEventListener('panzoompan', badPanListener)
       panzoom.pan(1, 1)
+      await skipFrame()
+      ;(div as any).removeEventListener('panzoompan', badPanListener)
       let pan = panzoom.getPan()
       assert.strictEqual(pan.x, 0)
       assert.strictEqual(pan.y, 0)
+      const goodPanListener = () => {
+        assert.ok(true, 'panzoompan event should not be triggered')
+      }
+      ;(div as any).addEventListener('panzoompan', goodPanListener)
+
+      // force option bypasses
       panzoom.pan(1, 1, { force: true })
+      await skipFrame()
+      ;(div as any).removeEventListener('panzoompan', goodPanListener)
       pan = panzoom.getPan()
       assert.strictEqual(pan.x, 1)
       assert.strictEqual(pan.y, 1)
       document.body.removeChild(div)
     })
-    it('ignores disableZoom', () => {
+    it('disableZoom', () => {
       const div = document.createElement('div')
       document.body.appendChild(div)
       const panzoom = Panzoom(div)
@@ -309,22 +322,31 @@ describe('Panzoom', () => {
       panzoom.zoom(2)
       let scale = panzoom.getScale()
       assert.strictEqual(scale, 1)
+
+      // force option bypasses
       panzoom.zoom(2, { force: true })
       scale = panzoom.getScale()
       assert.strictEqual(scale, 2)
       document.body.removeChild(div)
     })
-    it('ignores panOnlyWhenZoomed', () => {
+    it('panOnlyWhenZoomed', () => {
       const div = document.createElement('div')
       document.body.appendChild(div)
       const panzoom = Panzoom(div)
       panzoom.setOptions({
         panOnlyWhenZoomed: true
       })
+      const panListener = () => {
+        assert.ok(false, 'panzoompan event should not be triggered')
+      }
+      ;(div as any).addEventListener('panzoompan', panListener)
       panzoom.pan(1, 1)
+      ;(div as any).removeEventListener('panzoompan', panListener)
       let pan = panzoom.getPan()
       assert.strictEqual(pan.x, 0)
       assert.strictEqual(pan.y, 0)
+
+      // force option bypasses
       panzoom.pan(1, 1, { force: true })
       pan = panzoom.getPan()
       assert.strictEqual(pan.x, 1)