From a1ff60bf9be4fd0eb569ac2b13cf189d700a048b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Iv=C3=A1n=20S=C3=A1nchez=20Ortega?= <ivan@mazemap.no>
Date: Thu, 4 Feb 2016 12:27:23 +0100
Subject: [PATCH] Make wheel-zoom speed depend on a new wheelPxPerZoomLevel
 option

---
 debug/map/zoom-delta.html              |  6 ++++--
 src/map/handler/Map.ScrollWheelZoom.js | 10 ++++++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/debug/map/zoom-delta.html b/debug/map/zoom-delta.html
index ee449a6c..5c86dd82 100644
--- a/debug/map/zoom-delta.html
+++ b/debug/map/zoom-delta.html
@@ -71,7 +71,8 @@
 			layers: [osm1],
 			zoom: 5,
 			zoomSnap: 0.25,
-			zoomDelta: 0.5
+			zoomDelta: 0.5,
+			wheelPxPerZoomLevel: 50
 		});
 
 		var map2 = new L.Map('map2', {
@@ -79,7 +80,8 @@
 			layers: [osm2],
 			zoom: 5,
 			zoomSnap: 0,
-			zoomDelta: 0.25
+			zoomDelta: 0.25,
+			wheelPxPerZoomLevel: 50
 		});
 
 		map1.on('zoomend',function(){
diff --git a/src/map/handler/Map.ScrollWheelZoom.js b/src/map/handler/Map.ScrollWheelZoom.js
index d6f17406..55a3afbc 100644
--- a/src/map/handler/Map.ScrollWheelZoom.js
+++ b/src/map/handler/Map.ScrollWheelZoom.js
@@ -4,7 +4,8 @@
 
 L.Map.mergeOptions({
 	scrollWheelZoom: true,
-	wheelDebounceTime: 40
+	wheelDebounceTime: 40,
+	wheelPxPerZoomLevel: 50
 });
 
 L.Map.ScrollWheelZoom = L.Handler.extend({
@@ -45,9 +46,10 @@ L.Map.ScrollWheelZoom = L.Handler.extend({
 		map._stop(); // stop panning and fly animations if any
 
 		// map the delta with a sigmoid function to -4..4 range leaning on -1..1
-		var d2 = Math.ceil(4 * Math.log(2 / (1 + Math.exp(-Math.abs(this._delta / 200)))) / Math.LN2),
-		    d3 = d2 * this._map.options.zoomDelta,
-		delta = map._limitZoom(zoom + (this._delta > 0 ? d3 : -d3)) - zoom;
+		var d2 = this._delta / (this._map.options.wheelPxPerZoomLevel * 4),
+		    d3 = 4 * Math.log(2 / (1 + Math.exp(-Math.abs(d2)))) / Math.LN2,
+		    d4 = Math.max(d3, this._map.options.zoomSnap || 0),
+		    delta = map._limitZoom(zoom + (this._delta > 0 ? d4 : -d4)) - zoom;
 
 		this._delta = 0;
 		this._startTime = null;