From 2e5a9c20bcdb19e43fecb5a62c99027c8dcaf734 Mon Sep 17 00:00:00 2001
From: Vivia Nikolaidou <vivia@ahiru.eu>
Date: Sat, 28 Sep 2024 20:48:05 +0200
Subject: [PATCH] fix(ui): Fix zoom level after zooming in and back out again
 not ending up where it started

---
 frontend/src/map/Map.tsx | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/frontend/src/map/Map.tsx b/frontend/src/map/Map.tsx
index 93b2e9a581..64789a1745 100644
--- a/frontend/src/map/Map.tsx
+++ b/frontend/src/map/Map.tsx
@@ -48,8 +48,7 @@ export const MapContainer = styled(Box)({
 });
 
 const SCROLL_PARAMETERS = {
-    ZOOM_IN_MULTIPLIER: 4/3 - 1,
-    ZOOM_OUT_MULTIPLIER: 1 - 3/4,
+    ZOOM_MULTIPLIER: 1/4,
     PIXELS_PER_FULL_STEP: 100
 };
 
@@ -476,9 +475,13 @@ abstract class Map<P, S> extends React.Component<P & MapProps, S & MapState > {
             }
         }, 250);
 
-
-        const fullStep = evt.deltaY < 0 ? SCROLL_PARAMETERS.ZOOM_IN_MULTIPLIER : SCROLL_PARAMETERS.ZOOM_OUT_MULTIPLIER;
-        let factor = 1 - (fullStep * (evt.deltaY / SCROLL_PARAMETERS.PIXELS_PER_FULL_STEP));
+        const scaledPixels = evt.deltaY * (SCROLL_PARAMETERS.ZOOM_MULTIPLIER / SCROLL_PARAMETERS.PIXELS_PER_FULL_STEP);
+        let factor;
+        if (evt.deltaY < 0) {
+            factor = 1 / (1 + scaledPixels);
+        } else {
+            factor = 1 - scaledPixels;
+        }
 
         const { scaleX: currentScaleFactor } = this.ctxWrapper.getScaleFactor();