From 11bc79520a8a048fe05326cfb65c3e69f9967d1f Mon Sep 17 00:00:00 2001
From: Tamius Han <tamius.han@gmail.com>
Date: Sun, 22 Jan 2023 16:05:07 +0100
Subject: [PATCH] ANGLE detection

---
 .../lib/angle-detect/detect-angle-backend.ts  | 122 ++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 src/ext/lib/angle-detect/detect-angle-backend.ts

diff --git a/src/ext/lib/angle-detect/detect-angle-backend.ts b/src/ext/lib/angle-detect/detect-angle-backend.ts
new file mode 100644
index 0000000..08db21a
--- /dev/null
+++ b/src/ext/lib/angle-detect/detect-angle-backend.ts
@@ -0,0 +1,122 @@
+/**
+ * Used to detect ANGLE backend
+ */
+
+export enum AngleVersion {
+  OpenGL,
+  D3D9,
+  D3D11,
+  Metal,
+  Vulkan,
+  NotAvailable,
+}
+
+/**
+ * Detects DirectX version. Note that D3D11 and D3D11on12
+ * do not seem to be distinguishable
+ * @param shaderSource
+ * @returns
+ */
+function detectDX(shaderSource: string) {
+  const glsl = shaderSource.match(/#version (\d+)( es)?$/m);
+
+  const glslVer = +glsl[1];
+
+  if (glslVer >= 300) {
+    return AngleVersion.D3D11;
+  }
+  if (glslVer >= 100) {
+    return AngleVersion.D3D9;
+  }
+}
+
+/**
+ * Detects OpenGL version.
+ */
+function detectGl(shaderSource: string) {
+  // const glsl = shaderSource.match(/#version (\d+)( es)?$/m);
+  // if (glsl && glsl[1]) {
+  //   // GLSL version to OpenGL
+  //   // https://en.wikipedia.org/wiki/OpenGL_Shading_Language
+  //   const OpenGL = {
+  //     100: "OpenGL ES 2.0",
+  //     300: "OpenGL ES 3.0",
+  //     110: "OpenGL 2.0",
+  //     120: "OpenGL 2.1",
+  //     130: "OpenGL 3.0",
+  //     140: "OpenGL 3.1",
+  //     150: "OpenGL 3.2",
+  //     330: "OpenGL 3.3",
+  //     400: "OpenGL 4.0",
+  //     410: "OpenGL 4.1",
+  //     420: "OpenGL 4.2",
+  //     430: "OpenGL 4.3",
+  //     440: "OpenGL 4.4",
+  //     450: "OpenGL 4.5",
+  //     460: "OpenGL 4.6",
+  //   };
+
+  //   return AngleVersion.OpenGL
+  // }
+
+  return AngleVersion.OpenGL;
+}
+
+/**
+ * Detects angle backend version. Vulkan detection not implemented.
+ * @param str
+ * @returns
+ */
+function detectBackend(str) {
+
+  if (str.match(/metal::float4/)) {
+    return AngleVersion.Metal;
+  }
+
+  if (str.match(/VS_OUTPUT main\(/)) {
+    return detectDX(str);
+  }
+
+  return detectGl(str);
+}
+
+/**
+ * Checks which ANGLE backend is being used.
+ * Known limitations: D11on12 cannot be detected.
+ * @returns
+ */
+function detectANGLEBackend(): AngleVersion {
+  const canvas = document.createElement("canvas");
+  const gl = canvas.getContext("webgl2") ||
+    canvas.getContext("webgl") ||
+    canvas.getContext("experimental-webgl");
+
+  const ext = (gl as any).getExtension("WEBGL_debug_shaders");
+
+  if (!ext) {
+    return AngleVersion.NotAvailable;
+  }
+
+  const isWebGL1 = gl instanceof WebGLRenderingContext;
+  const shader = (gl as any).createShader((gl as any).VERTEX_SHADER);
+
+  (gl as any).shaderSource(
+    shader,
+    `#version ${isWebGL1 ? "100" : "300 es"}
+    void main() {
+      gl_Position = vec4(__VERSION__, 1.0, 1.0, 1.0);
+    }
+  `
+  );
+
+  (gl as any).compileShader(shader);
+
+  if (!(gl as any).getShaderParameter(shader, (gl as any).COMPILE_STATUS)) {
+    return console.error("invalid shader", (gl as any).getShaderInfoLog(shader));
+  }
+
+  const source = ext.getTranslatedShaderSource(shader);
+
+  return detectBackend(source);
+}
+