fix/webgl2 as default

.github/workflows/pages.yml

@@ -39,8 +39,9 @@ jobs:
       # `ring` (under iroh) compiles C for wasm32, which needs clang and llvm-ar.
       - name: clang
         run: sudo apt-get update && sudo apt-get install -y --no-install-recommends clang llvm
-      # The WebGL2 build and the WebGPU one: the page picks by what the browser has.
-      - run: ./web/build.sh dist both
+      # WebGL2 only. The WebGPU build (`web/build.sh dist both`, then `?backend=webgpu`) is left out
+      # until it draws dependably.
+      - run: ./web/build.sh dist webgl2
         env:
           LLVM: /usr
       - uses: actions/upload-pages-artifact@v5

web/build.sh

@@ -1,8 +1,8 @@
 #!/bin/sh
 # Usage: web/build.sh [release|dev|dist] [webgl2|webgpu|both], into target/web. Needs
 # wasm-bindgen-cli at Cargo.lock's version, wasm-opt for dist, and an LLVM clang that targets wasm
-# (brew install llvm, or LLVM=<prefix>). The page draws through WebGPU where the browser has it and
-# that build was made, and through WebGL2 elsewhere; with webgpu alone, a browser without WebGPU
+# (brew install llvm, or LLVM=<prefix>). The page draws through WebGL2, and through WebGPU only when
+# asked (`?backend=webgpu`) or when that is the only build made; then a browser without WebGPU
 # shows nothing.
 set -eu
 cd "$(dirname "$0")/.."

web/play.html

@@ -193,16 +193,17 @@ <h1><a href="../">CTR-RS</a></h1>
 // The builds of the game here, one for each way of drawing: `web/build.sh` puts the ones it made
 // in this list.
 const BUILT = ["webgl2"];
-// WebGPU where the browser has it (and an adapter to give), WebGL2 elsewhere.
+// WebGL2, unless `?backend=webgpu` asks for the WebGPU build (or it is the only one made). WebGPU is
+// opt-in for now: it has been the less dependable of the two, and WebKit's WGSL compiler (Safari,
+// and every browser on iOS) holds to the spec where Chrome's and naga's do not, and rejects Bevy's
+// PBR shader for its texture-typed `let`s.
+const asked = new URLSearchParams(location.search).get("backend");
 const backend = (async () => {
-  if (BUILT.includes("webgpu")) {
-    try {
-      if ((await navigator.gpu?.requestAdapter({ powerPreference: "high-performance" })) != null) {
-        return "webgpu";
-      }
-    } catch (e) {
-      console.warn(`could not ask for WebGPU: ${e}`);
+  if (asked != null) {
+    if (BUILT.includes(asked)) {
+      return asked;
     }
+    console.warn(`ctr-rs: backend=${asked} asked for, but the builds here are ${BUILT.join(", ")}`);
   }
   return BUILT.includes("webgl2") ? "webgl2" : BUILT[0];
 })();