From 2e34dd0fafdc40a0bdd2023db55514083b1da87c Mon Sep 17 00:00:00 2001
From: Frederic Junod <frederic.junod@camptocamp.com>
Date: Thu, 21 Mar 2019 10:42:18 +0100
Subject: [PATCH] Use HTMLImageElement.decode if available

---
 src/ol/Image.js           | 44 ++++++++++++++++++++++++++++++++-------
 src/ol/ImageTile.js       | 17 +++++++--------
 src/ol/style/IconImage.js | 17 +++++++--------
 3 files changed, 51 insertions(+), 27 deletions(-)

diff --git a/src/ol/Image.js b/src/ol/Image.js
index fdfec05be1..45d0cf07cf 100644
--- a/src/ol/Image.js
+++ b/src/ol/Image.js
@@ -120,13 +120,12 @@ class ImageWrapper extends ImageBase {
     if (this.state == ImageState.IDLE || this.state == ImageState.ERROR) {
       this.state = ImageState.LOADING;
       this.changed();
-      this.imageListenerKeys_ = [
-        listenOnce(this.image_, EventType.ERROR,
-          this.handleImageError_, this),
-        listenOnce(this.image_, EventType.LOAD,
-          this.handleImageLoad_, this)
-      ];
       this.imageLoadFunction_(this, this.src_);
+      this.imageListenerKeys_ = listenImage(
+        this.image_,
+        this.handleImageLoad_.bind(this),
+        this.handleImageError_.bind(this)
+      );
     }
   }
 
@@ -143,10 +142,39 @@ class ImageWrapper extends ImageBase {
    * @private
    */
   unlistenImage_() {
-    this.imageListenerKeys_.forEach(unlistenByKey);
-    this.imageListenerKeys_ = null;
+    unlistenImage(this.imageListenerKeys_);
   }
 }
 
+/**
+ * @param {HTMLCanvasElement|HTMLImageElement|HTMLVideoElement} image Image element.
+ * @param {function():any} loadHandler Load callback function.
+ * @param {function():any} errorHandler Error callback function.
+ * @return {Array<import("./events.js").EventsKey>} listener keys.
+ */
+export function listenImage(image, loadHandler, errorHandler) {
+  const img = /** @type {HTMLImageElement} */ (image);
+  if (img.decode) {
+    img.decode().then(loadHandler).catch(errorHandler);
+    return null;
+  } else {
+    const listenerKeys = [
+      listenOnce(img, EventType.LOAD, loadHandler),
+      listenOnce(img, EventType.ERROR, errorHandler)
+    ];
+    return listenerKeys;
+  }
+
+}
+
+/**
+ * @param {Array<import("./events.js").EventsKey>} listenerKeys listener keys.
+ */
+export function unlistenImage(listenerKeys) {
+  if (listenerKeys) {
+    listenerKeys.forEach(unlistenByKey);
+    listenerKeys = null;
+  }
+}
 
 export default ImageWrapper;
diff --git a/src/ol/ImageTile.js b/src/ol/ImageTile.js
index a5ae93b667..b6a5496e03 100644
--- a/src/ol/ImageTile.js
+++ b/src/ol/ImageTile.js
@@ -4,8 +4,7 @@
 import Tile from './Tile.js';
 import TileState from './TileState.js';
 import {createCanvasContext2D} from './dom.js';
-import {listenOnce, unlistenByKey} from './events.js';
-import EventType from './events/EventType.js';
+import {listenImage, unlistenImage} from './Image.js';
 
 
 class ImageTile extends Tile {
@@ -134,13 +133,12 @@ class ImageTile extends Tile {
     if (this.state == TileState.IDLE) {
       this.state = TileState.LOADING;
       this.changed();
-      this.imageListenerKeys_ = [
-        listenOnce(this.image_, EventType.ERROR,
-          this.handleImageError_, this),
-        listenOnce(this.image_, EventType.LOAD,
-          this.handleImageLoad_, this)
-      ];
       this.tileLoadFunction_(this, this.src_);
+      this.imageListenerKeys_ = listenImage(
+        this.image_,
+        this.handleImageLoad_.bind(this),
+        this.handleImageError_.bind(this)
+      );
     }
   }
 
@@ -150,8 +148,7 @@ class ImageTile extends Tile {
    * @private
    */
   unlistenImage_() {
-    this.imageListenerKeys_.forEach(unlistenByKey);
-    this.imageListenerKeys_ = null;
+    unlistenImage(this.imageListenerKeys_);
   }
 }
 
diff --git a/src/ol/style/IconImage.js b/src/ol/style/IconImage.js
index 8f1cc8069f..45214a22cd 100644
--- a/src/ol/style/IconImage.js
+++ b/src/ol/style/IconImage.js
@@ -3,11 +3,12 @@
  */
 
 import {createCanvasContext2D} from '../dom.js';
-import {listenOnce, unlistenByKey} from '../events.js';
 import EventTarget from '../events/Target.js';
 import EventType from '../events/EventType.js';
 import ImageState from '../ImageState.js';
 import {shared as iconImageCache} from './IconImageCache.js';
+import {listenImage, unlistenImage} from '../Image.js';
+
 
 class IconImage extends EventTarget {
   /**
@@ -185,17 +186,16 @@ class IconImage extends EventTarget {
   load() {
     if (this.imageState_ == ImageState.IDLE) {
       this.imageState_ = ImageState.LOADING;
-      this.imageListenerKeys_ = [
-        listenOnce(this.image_, EventType.ERROR,
-          this.handleImageError_, this),
-        listenOnce(this.image_, EventType.LOAD,
-          this.handleImageLoad_, this)
-      ];
       try {
         /** @type {HTMLImageElement} */ (this.image_).src = this.src_;
       } catch (e) {
         this.handleImageError_();
       }
+      this.imageListenerKeys_ = listenImage(
+        this.image_,
+        this.handleImageLoad_.bind(this),
+        this.handleImageError_.bind(this)
+      );
     }
   }
 
@@ -233,8 +233,7 @@ class IconImage extends EventTarget {
    * @private
    */
   unlistenImage_() {
-    this.imageListenerKeys_.forEach(unlistenByKey);
-    this.imageListenerKeys_ = null;
+    unlistenImage(this.imageListenerKeys_);
   }
 }