1 files changed, 46 insertions, 0 deletions
diff --git a/src/lib/test/canvas/detect-canvas-block.ts b/src/lib/test/canvas/detect-canvas-block.ts
new file mode 100644
index 0000000..4557213
--- /dev/null
+++ b/src/lib/test/canvas/detect-canvas-block.ts
@@ -0,0 +1,46 @@
+export const detect2dCanvasBlockOnCanvas = (canvas: HTMLCanvasElement, resetDimensions = true, canvasOpts: CanvasRenderingContext2D | CanvasRenderingContext2DSettings = {
+  desynchronized: true,
+  alpha: true,
+  willReadFrequently: false,
+  // @ts-ignore type is incomplete
+  colorType: 'float16' as const,
+  colorSpace: 'display-p3' as const,
+}): null | Error => {
+  const dimensions = resetDimensions ? [canvas.width, canvas.height] as const : [0, 0] as const;
+  const [w, h] = [255, 255];
+  const checks = 32;
+  const ctx = canvasOpts instanceof CanvasRenderingContext2D && canvasOpts && canvasOpts.canvas.width >= 256 && canvasOpts.canvas.height >= 256 ? canvasOpts : (() => {
+    [canvas.width, canvas.height] = [w, h];
+    return canvas.getContext('2d', canvasOpts) as CanvasRenderingContext2D | null
+  })();
+  if (ctx) {
+    try {
+      // make sure we have canvas support
+      ctx.fillStyle = '#0099ff';
+      ctx.fillRect(0, 0, w, h);
+      for (let i = 0; i < checks; i++) {
+        const data = ctx.getImageData(i % w, i % h, 1, 1).data;
+        if (
+          data[0] !== 0 ||
+          data[1] !== 153 ||
+          data[2] !== 255 ||
+          data[3] !== 255
+        ) {
+          if (resetDimensions) [canvas.width, canvas.height] = dimensions;
+          return new Error("Canvas Data doesn't match written data.");
+        }
+      }
+      ctx.clearRect(0, 0, w, h);
+    } catch (error) {
+      if (resetDimensions) [canvas.width, canvas.height] = dimensions;
+      return new Error('No canvas support', {
+        cause: error
+      });
+    }
+  } else {
+    if (resetDimensions) [canvas.width, canvas.height] = dimensions;
+    return new Error('No canvas support: ctx is undefined.');
+  }
+  return null;
+}
+export const checkFor2dCanvasSupport = () => detect2dCanvasBlockOnCanvas(document.createElement('canvas'), false)