From b7a6285ecf53ad0517719ab01fe1aa3e2c331501 Mon Sep 17 00:00:00 2001
From: Douglass Turner <douglass.turner@gmail.com>
Date: Mon, 18 Oct 2021 18:18:01 -0400
Subject: [PATCH] Git Issue 1400 (#1404)

---
 js/browser.js       | 10 ++++++++++
 js/ui/zoomWidget.js |  6 ++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/js/browser.js b/js/browser.js
index d22ec490f..d11d0d13d 100755
--- a/js/browser.js
+++ b/js/browser.js
@@ -1198,6 +1198,16 @@ class Browser {
         return this.config.minimumBases;
     }
 
+    // Zoom in by a factor of 2, keeping the same center location
+    zoomIn() {
+        this.zoomWithScaleFactor(0.5)
+    };
+
+    // Zoom out by a factor of 2, keeping the same center location if possible
+    zoomOut() {
+        this.zoomWithScaleFactor(2.0)
+    };
+
     async zoomWithScaleFactor(scaleFactor, centerBPOrUndefined, referenceFrameOrUndefined) {
 
         const viewportWidth = this.calculateViewportWidth(this.referenceFrameList.length)
diff --git a/js/ui/zoomWidget.js b/js/ui/zoomWidget.js
index 639c3febe..760dabb6f 100644
--- a/js/ui/zoomWidget.js
+++ b/js/ui/zoomWidget.js
@@ -43,7 +43,8 @@ const ZoomWidget = function (browser, parent) {
     this.zoomContainer.appendChild(this.zoomOutButton)
     this.zoomOutButton.appendChild(Icon.createIcon('minus-circle'))
     this.zoomOutButton.addEventListener('click', () => {
-        browser.zoomWithScaleFactor(2.0)
+        // browser.zoomWithScaleFactor(2.0)
+        browser.zoomOut()
     })
 
     // Range slider
@@ -85,7 +86,8 @@ const ZoomWidget = function (browser, parent) {
     this.zoomContainer.appendChild(this.zoomInButton)
     this.zoomInButton.appendChild(Icon.createIcon('plus-circle'))
     this.zoomInButton.addEventListener('click', () => {
-        browser.zoomWithScaleFactor(0.5)
+        // browser.zoomWithScaleFactor(0.5)
+        browser.zoomIn()
     })
 
     browser.on('locuschange', (referenceFrameList) => {