From 4e683650c1d203fbd72e7e06d8dc4e032fb58221 Mon Sep 17 00:00:00 2001
From: Erik Onarheim <erik.onarheim@gmail.com>
Date: Mon, 23 Sep 2024 08:01:24 -0500
Subject: [PATCH 1/3] fix: [#3215] Check shader complexity to avoid crash

---
 .../Context/image-renderer/image-renderer.ts  |  5 ++-
 src/engine/Graphics/Context/webgl-util.ts     | 42 +++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/src/engine/Graphics/Context/image-renderer/image-renderer.ts b/src/engine/Graphics/Context/image-renderer/image-renderer.ts
index 6021de77c..1a37fcab1 100644
--- a/src/engine/Graphics/Context/image-renderer/image-renderer.ts
+++ b/src/engine/Graphics/Context/image-renderer/image-renderer.ts
@@ -11,6 +11,7 @@ import { RendererPlugin } from '../renderer';
 import { Shader } from '../shader';
 import { VertexBuffer } from '../vertex-buffer';
 import { VertexLayout } from '../vertex-layout';
+import { getMaxShaderComplexity } from '../webgl-util';
 import frag from './image-renderer.frag.glsl';
 import vert from './image-renderer.vert.glsl';
 
@@ -54,7 +55,9 @@ export class ImageRenderer implements RendererPlugin {
     this._context = context;
     // Transform shader source
     // FIXME: PIXEL 6 complains `ERROR: Expression too complex.` if we use it's reported max texture units, 125 seems to work for now...
-    this._maxTextures = Math.min(gl.getParameter(gl.MAX_TEXTURE_IMAGE_UNITS), 125);
+    const maxTexture = gl.getParameter(gl.MAX_TEXTURE_IMAGE_UNITS);
+    const maxComplexity = getMaxShaderComplexity(gl, maxTexture);
+    this._maxTextures = Math.min(maxTexture, maxComplexity);
     const transformedFrag = this._transformFragmentSource(frag, this._maxTextures);
     // Compile shader
     this._shader = new Shader({
diff --git a/src/engine/Graphics/Context/webgl-util.ts b/src/engine/Graphics/Context/webgl-util.ts
index 5903b12e8..c70679355 100644
--- a/src/engine/Graphics/Context/webgl-util.ts
+++ b/src/engine/Graphics/Context/webgl-util.ts
@@ -134,3 +134,45 @@ export function getAttributePointerType(gl: WebGLRenderingContext, type: number)
       return gl.FLOAT;
   }
 }
+
+/**
+ *
+ */
+export function getMaxShaderComplexity(gl: WebGL2RenderingContext, numIfs: number): number {
+  const assembleTestShader = (numIfs: number) => {
+    const testShader = `#version 300 es
+    precision mediump float;
+    out vec4 fragColor;
+    void main() {
+      float index = 1.01;
+      %%complexity%%
+    }`;
+    let testComplexity = '';
+    for (let i = 0; i < numIfs; i++) {
+      if (i === 0) {
+        testComplexity += `if (index <= ${i}.5) {\n`;
+      } else {
+        testComplexity += `   else if (index <= ${i}.5) {\n`;
+      }
+
+      testComplexity += `      fragColor = vec4(1.0);\n`;
+      testComplexity += `   }\n`;
+    }
+    return testShader.replace('%%complexity%%', testComplexity);
+  };
+
+  let canCompile = false;
+  do {
+    const test = assembleTestShader(numIfs);
+
+    const shader = gl.createShader(gl.FRAGMENT_SHADER)!;
+    gl.shaderSource(shader, test);
+    gl.compileShader(shader);
+
+    canCompile = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
+    if (!canCompile) {
+      numIfs = numIfs / 2;
+    }
+  } while (!canCompile);
+  return numIfs;
+}

From 6079b231ea34c3073632ebec24f6637fe4bb271c Mon Sep 17 00:00:00 2001
From: Erik Onarheim <erik.onarheim@gmail.com>
Date: Mon, 23 Sep 2024 09:19:30 -0500
Subject: [PATCH 2/3] coerce an integer

---
 src/engine/Graphics/Context/webgl-util.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/engine/Graphics/Context/webgl-util.ts b/src/engine/Graphics/Context/webgl-util.ts
index c70679355..6027059cc 100644
--- a/src/engine/Graphics/Context/webgl-util.ts
+++ b/src/engine/Graphics/Context/webgl-util.ts
@@ -171,7 +171,7 @@ export function getMaxShaderComplexity(gl: WebGL2RenderingContext, numIfs: numbe
 
     canCompile = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
     if (!canCompile) {
-      numIfs = numIfs / 2;
+      numIfs = (numIfs / 2) | 0;
     }
   } while (!canCompile);
   return numIfs;

From e2455c064df97a7145ee2e550ee9352757566945 Mon Sep 17 00:00:00 2001
From: Erik Onarheim <erik.onarheim@gmail.com>
Date: Mon, 23 Sep 2024 09:35:02 -0500
Subject: [PATCH 3/3] Add changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5b1c910d0..c836953dc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -104,6 +104,7 @@ are doing mtv adjustments during precollision.
 
 ### Fixed
 
+- Fixed issue where certain devices that support large numbers of texture slots exhaust the maximum number of if statements (complexity) in the shader.
 - Fixed issue where `ex.Label` where setting the opacity of caused a multiplicative opacity effect when actor opacity set
 - Fixed issue where the `ex.Loader` would have a low res logo on small configured resolution sizes
 - Fixed issue where `ex.Gif` was not parsing certain binary formats correctly