From 80b3c4376ca1e36daeac185439c9293c82cd830a Mon Sep 17 00:00:00 2001
From: Jeff Pamer <jeffrey.r.pamer@jpl.nasa.gov>
Date: Mon, 11 Dec 2023 12:31:39 -0800
Subject: [PATCH] Add fallback support for standard Canvas if OffscreenCanvas
 unavailable (#1052)

---
 src/components/timeline/LayerLine.svelte | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/components/timeline/LayerLine.svelte b/src/components/timeline/LayerLine.svelte
index a0172bd374..0e05edb2c3 100644
--- a/src/components/timeline/LayerLine.svelte
+++ b/src/components/timeline/LayerLine.svelte
@@ -192,13 +192,25 @@
     return points;
   }
 
-  function generateOffscreenPoint(lineColor: string, radius: number): OffscreenCanvas | null {
+  function generateOffscreenPoint(lineColor: string, radius: number): OffscreenCanvas | HTMLCanvasElement | null {
     if (!radius) {
       return null;
     }
 
-    const tempCanvas = new OffscreenCanvas(radius * 2 * dpr, radius * 2 * dpr);
-    const tempCtx = tempCanvas.getContext('2d');
+    let tempCanvas: OffscreenCanvas | HTMLCanvasElement;
+    let tempCtx: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D | null;
+
+    if ('OffscreenCanvas' in window) {
+      tempCanvas = new OffscreenCanvas(radius * 2 * dpr, radius * 2 * dpr);
+    } else {
+      tempCanvas = document.createElement('canvas');
+      tempCanvas.height = radius * 2 * dpr;
+      tempCanvas.width = radius * 2 * dpr;
+      tempCanvas.style.height = `${radius * 2}px`;
+      tempCanvas.style.width = `${radius * 2}px`;
+    }
+
+    tempCtx = tempCanvas.getContext('2d');
 
     if (!tempCtx) {
       return null;