From 8fe71bbbff95eb96f91ab8b046ffa09a6dbdb9cb Mon Sep 17 00:00:00 2001
From: John Leonard <jellyedwards@hotmail.com>
Date: Fri, 14 Feb 2020 11:39:54 +0000
Subject: [PATCH] perf: only do expensive reload when texture changes

---
 src/ol/webgl/Helper.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/ol/webgl/Helper.js b/src/ol/webgl/Helper.js
index cf2ceeab3a..ce97b33a01 100644
--- a/src/ol/webgl/Helper.js
+++ b/src/ol/webgl/Helper.js
@@ -558,6 +558,7 @@ class WebGLHelper extends Disposable {
       if (value instanceof HTMLCanvasElement || value instanceof HTMLImageElement || value instanceof ImageData) {
         // create a texture & put data
         if (!uniform.texture) {
+          uniform.prevValue = undefined;
           uniform.texture = gl.createTexture();
         }
         gl.activeTexture(gl[`TEXTURE${textureSlot}`]);
@@ -567,7 +568,8 @@ class WebGLHelper extends Disposable {
         gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
 
         const imageReady = !(value instanceof HTMLImageElement) || /** @type {HTMLImageElement} */(value).complete;
-        if (imageReady) {
+        if (imageReady && uniform.prevValue !== value) {
+          uniform.prevValue = value;
           gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, value);
         }