From fefcc9f0caea9f4fd72a717c853fdcc50e9c9a38 Mon Sep 17 00:00:00 2001
From: ahocevar <andreas.hocevar@gmail.com>
Date: Mon, 18 Mar 2019 21:32:55 +0100
Subject: [PATCH] Return directly when all we do is render queued images

---
 src/ol/renderer/canvas/TileLayer.js       | 9 ++++++++-
 src/ol/renderer/canvas/VectorTileLayer.js | 7 ++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/ol/renderer/canvas/TileLayer.js b/src/ol/renderer/canvas/TileLayer.js
index 03b29a026f..a2d601b6e6 100644
--- a/src/ol/renderer/canvas/TileLayer.js
+++ b/src/ol/renderer/canvas/TileLayer.js
@@ -4,7 +4,7 @@
 import {getUid} from '../../util.js';
 import TileRange from '../../TileRange.js';
 import TileState from '../../TileState.js';
-import {createEmpty, getIntersection, getTopLeft} from '../../extent.js';
+import {createEmpty, equals, getIntersection, getTopLeft} from '../../extent.js';
 import CanvasLayerRenderer from './Layer.js';
 import {apply as applyTransform, compose as composeTransform, makeInverse, toString as transformToString} from '../../transform.js';
 
@@ -21,6 +21,12 @@ class CanvasTileLayerRenderer extends CanvasLayerRenderer {
   constructor(tileLayer) {
     super(tileLayer);
 
+    /**
+     * Rendered extent has changed since the previous `renderFrame()` call
+     * @type {boolean}
+     */
+    this.extentChanged = true;
+
     /**
      * @private
      * @type {import("../../extent.js").Extent}
@@ -301,6 +307,7 @@ class CanvasTileLayerRenderer extends CanvasLayerRenderer {
 
     this.renderedRevision = sourceRevision;
     this.renderedResolution = tileResolution;
+    this.extentChanged = !this.renderedExtent_ || !equals(this.renderedExtent_, canvasExtent);
     this.renderedExtent_ = canvasExtent;
 
     this.manageTilePyramid(frameState, tileSource, tileGrid, pixelRatio,
diff --git a/src/ol/renderer/canvas/VectorTileLayer.js b/src/ol/renderer/canvas/VectorTileLayer.js
index 60ed514aad..beaa29dcaf 100644
--- a/src/ol/renderer/canvas/VectorTileLayer.js
+++ b/src/ol/renderer/canvas/VectorTileLayer.js
@@ -27,7 +27,7 @@ import {
   makeInverse
 } from '../../transform.js';
 import CanvasExecutorGroup, {replayDeclutter} from '../../render/canvas/ExecutorGroup.js';
-import {clear} from '../../obj.js';
+import {clear, isEmpty} from '../../obj.js';
 
 
 /**
@@ -432,6 +432,11 @@ class CanvasVectorTileLayerRenderer extends CanvasTileLayerRenderer {
       return this.container_;
     }
 
+    if (!isEmpty(this.renderTileImageQueue_) && !this.extentChanged) {
+      this.renderTileImages_(hifi, frameState);
+      return this.container_;
+    }
+
     const context = this.overlayContext_;
     const declutterReplays = layer.getDeclutter() ? {} : null;
     const source = layer.getSource();