From ab28c4833827c7bee0796e504747e781afa7dae6 Mon Sep 17 00:00:00 2001
From: Frederic Junod <frederic.junod@camptocamp.com>
Date: Wed, 14 Feb 2018 14:51:51 +0100
Subject: [PATCH] Only compute the viewState focus when it's needed

---
 src/ol/PluggableMap.js | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/ol/PluggableMap.js b/src/ol/PluggableMap.js
index 82bd7dee49..83c1869fce 100644
--- a/src/ol/PluggableMap.js
+++ b/src/ol/PluggableMap.js
@@ -1208,15 +1208,18 @@ PluggableMap.prototype.renderFrame_ = function(time) {
       layerStates[getUid(layerStatesArray[i].layer)] = layerStatesArray[i];
     }
     viewState = view.getState();
-    const center = viewState.center;
-    const pixelResolution = viewState.resolution / this.pixelRatio_;
-    center[0] = Math.round(center[0] / pixelResolution) * pixelResolution;
-    center[1] = Math.round(center[1] / pixelResolution) * pixelResolution;
+    let focus = this.focus_;
+    if (!focus) {
+      focus = viewState.center;
+      const pixelResolution = viewState.resolution / this.pixelRatio_;
+      focus[0] = Math.round(focus[0] / pixelResolution) * pixelResolution;
+      focus[1] = Math.round(focus[1] / pixelResolution) * pixelResolution;
+    }
     frameState = /** @type {olx.FrameState} */ ({
       animate: false,
       coordinateToPixelTransform: this.coordinateToPixelTransform_,
       extent: extent,
-      focus: !this.focus_ ? center : this.focus_,
+      focus: focus,
       index: this.frameIndex_++,
       layerStates: layerStates,
       layerStatesArray: layerStatesArray,