Fix MSAA hang for Mali-G71 and Mali-G76 GPUs (#3499)

common/api/webgl-compatibility.api.md

@@ -105,6 +105,7 @@ export enum DepthType {
 // @public
 export interface GraphicsDriverBugs {
     fragDepthDoesNotDisableEarlyZ?: true;
+    msaaWillHang?: true;
 }
 
 // @public

common/changes/@itwin/webgl-compatibility/markschlosser-fix-msaa-hang-malig71-malig76_2022-04-08-13-29.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@itwin/webgl-compatibility",
+      "comment": "Do not allow buggy GPUs to render MSAA.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@itwin/webgl-compatibility"
+}

core/webgl-compatibility/src/Capabilities.ts

@@ -73,6 +73,12 @@ const buggyIntelMatchers = [
   /ANGLE \(Intel, Intel\(R\) (U)?HD Graphics 6(2|3)0 Direct3D11/,
 ];
 
+// Regexes to match Mali GPUs known to suffer from GraphicsDriverBugs.msaaWillHang.
+const buggyMaliMatchers = [
+  /Mali-G71/,
+  /Mali-G76/,
+];
+
 // Regexes to match as many Intel integrated GPUs as possible.
 // https://en.wikipedia.org/wiki/List_of_Intel_graphics_processing_units
 const integratedIntelGpuMatchers = [
@@ -254,6 +260,16 @@ export class Capabilities {
 
     this._isMobile = ProcessDetector.isMobileBrowser;
 
+    const debugInfo = gl.getExtension("WEBGL_debug_renderer_info");
+    const unmaskedRenderer = debugInfo !== null ? gl.getParameter(debugInfo.UNMASKED_RENDERER_WEBGL) : undefined;
+    const unmaskedVendor = debugInfo !== null ? gl.getParameter(debugInfo.UNMASKED_VENDOR_WEBGL) : undefined;
+
+    this._driverBugs = {};
+    if (unmaskedRenderer && buggyIntelMatchers.some((x) => x.test(unmaskedRenderer)))
+      this._driverBugs.fragDepthDoesNotDisableEarlyZ = true;
+    if (unmaskedRenderer && buggyMaliMatchers.some((x) => x.test(unmaskedRenderer)))
+      this._driverBugs.msaaWillHang = true;
+
     this._maxTextureSize = gl.getParameter(gl.MAX_TEXTURE_SIZE);
     this._supportsCreateImageBitmap = typeof createImageBitmap === "function" && ProcessDetector.isChromium && !ProcessDetector.isIOSBrowser;
     this._maxTexSizeAllow = Math.min(this._maxTextureSize, maxTexSizeAllowed);
@@ -263,7 +279,7 @@ export class Capabilities {
     this._maxVertUniformVectors = gl.getParameter(gl.MAX_VERTEX_UNIFORM_VECTORS);
     this._maxVaryingVectors = gl.getParameter(gl.MAX_VARYING_VECTORS);
     this._maxFragUniformVectors = gl.getParameter(gl.MAX_FRAGMENT_UNIFORM_VECTORS);
-    this._maxAntialiasSamples = (this._isWebGL2 && undefined !== gl2 ? gl.getParameter(gl2.MAX_SAMPLES) : 1);
+    this._maxAntialiasSamples = this._driverBugs.msaaWillHang ? 1 : (this._isWebGL2 && undefined !== gl2 ? gl.getParameter(gl2.MAX_SAMPLES) : 1);
 
     const extensions = gl.getSupportedExtensions(); // This just retrieves a list of available extensions (not necessarily enabled).
     if (extensions) {
@@ -289,10 +305,6 @@ export class Capabilities {
       this._maxDrawBuffers = dbExt !== undefined ? gl.getParameter(dbExt.MAX_DRAW_BUFFERS_WEBGL) : 1;
     }
 
-    const debugInfo = gl.getExtension("WEBGL_debug_renderer_info");
-    const unmaskedRenderer = debugInfo !== null ? gl.getParameter(debugInfo.UNMASKED_RENDERER_WEBGL) : undefined;
-    const unmaskedVendor = debugInfo !== null ? gl.getParameter(debugInfo.UNMASKED_VENDOR_WEBGL) : undefined;
-
     // Determine the maximum color-renderable attachment type.
     const allowFloatRender =
       (undefined === disabledExtensions || -1 === disabledExtensions.indexOf("OES_texture_float"))
@@ -323,10 +335,6 @@ export class Capabilities {
     const missingRequiredFeatures = this._findMissingFeatures(Capabilities.requiredFeatures);
     const missingOptionalFeatures = this._findMissingFeatures(Capabilities.optionalFeatures);
 
-    this._driverBugs = {};
-    if (unmaskedRenderer && buggyIntelMatchers.some((x) => x.test(unmaskedRenderer)))
-      this._driverBugs.fragDepthDoesNotDisableEarlyZ = true;
-
     return {
       status: this._getCompatibilityStatus(missingRequiredFeatures, missingOptionalFeatures),
       missingRequiredFeatures,

core/webgl-compatibility/src/RenderCompatibility.ts

@@ -89,6 +89,13 @@ export interface GraphicsDriverBugs {
    * The workaround for this bug has minimal impact on performance and no impact on visual fidelity.
    */
   fragDepthDoesNotDisableEarlyZ?: true;
+  /** If true, the graphics driver will hang when applying MSAA to a viewport.
+   *
+   * Known to affect certain mobile Mali chipsets (G71 and G76). May affect more.
+   *
+   * The workaround for this bug means MSAA cannot be enabled on those devices.
+   */
+  msaaWillHang?: true;
 }
 
 /** Describes the level of compatibility of a client device/browser with the iTwin.js rendering system.

core/webgl-compatibility/src/test/Compatibility.test.ts

@@ -240,4 +240,30 @@ describe("Render Compatibility", () => {
       expect(compatibility.usingIntegratedGraphics).to.equal(renderer[1]);
     }
   });
+
+  it("detects MSAA hang bug", () => {
+    const renderers = [
+      [ "Mali-G71", true ],
+      [ "Mali-G76", true ],
+      [ "ANGLE (Intel HD Graphics 620 Direct3D11 vs_5_0 ps_5_0)",  false ],
+      [ "Mali-G79", false ],
+    ];
+
+    for (const renderer of renderers) {
+      overriddenFunctions.overrideCreateContext((ctx: WebGLContext, pname: number) => {
+        const ext = ctx.getExtension("WEBGL_debug_renderer_info");
+        if (ext && pname === ext.UNMASKED_RENDERER_WEBGL)
+          return renderer[0];
+
+        return undefined;
+      });
+
+      const context = makeTestContext(true);
+      const caps = new Capabilities();
+      const compatibility = caps.init(context);
+
+      const expected = renderer[1] ? true : undefined;
+      expect(compatibility.driverBugs.msaaWillHang).to.equal(expected);
+    }
+  });
 });