From d62b4531c3a6e72b964c4a6c4e8706a2b55be9fa Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Sat, 24 Sep 2022 06:58:01 -0700
Subject: [PATCH] Optimize contexts for reading frequently

This was a recommendation from Edge.
Docs here: https://html.spec.whatwg.org/multipage/canvas.html#concept-canvas-will-read-frequently
---
 addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts | 5 ++++-
 src/browser/ColorManager.ts                          | 4 +++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts b/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts
index 9ba83de6..092cf2e5 100644
--- a/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts
+++ b/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts
@@ -110,7 +110,10 @@ export class WebglCharAtlas implements IDisposable {
     this._tmpCanvas = document.createElement('canvas');
     this._tmpCanvas.width = this._config.scaledCellWidth * 4 + TMP_CANVAS_GLYPH_PADDING * 2;
     this._tmpCanvas.height = this._config.scaledCellHeight + TMP_CANVAS_GLYPH_PADDING * 2;
-    this._tmpCtx = throwIfFalsy(this._tmpCanvas.getContext('2d', { alpha: this._config.allowTransparency }));
+    this._tmpCtx = throwIfFalsy(this._tmpCanvas.getContext('2d', {
+      alpha: this._config.allowTransparency,
+      willReadFrequently: true
+    }));
   }
 
   public dispose(): void {
diff --git a/src/browser/ColorManager.ts b/src/browser/ColorManager.ts
index d8dcde6f..4ec0053c 100644
--- a/src/browser/ColorManager.ts
+++ b/src/browser/ColorManager.ts
@@ -89,7 +89,9 @@ export class ColorManager implements IColorManager {
     const canvas = document.createElement('canvas');
     canvas.width = 1;
     canvas.height = 1;
-    const ctx = canvas.getContext('2d');
+    const ctx = canvas.getContext('2d', {
+      willReadFrequently: true
+    });
     if (!ctx) {
       throw new Error('Could not get rendering context');
     }