web: Allow building an MVP vanilla WASM module

[danielhjacobs]

I'm not sure whether this itself will be controversial. By itself, this update changes nothing in the development or CI pipelines by default.

Instead, it adds an environment variable, BUILD_WASM_MVP, which when set will cause npm run build:dual-wasm and/or npm run build:repro to create a truly vanilla WASM module by using nightly Rust to disable all the WebAssembly extensions. With this set, the version of Ruffle that gets built can run on Pale Moon and Safari versions as old as 14.1.

What this doesn't do (yet) is use this environment variable on CI or in the Firefox Docker script. Doing that is a matter of debate. Once we unpin CI from Rust 1.81, if we don't use this environment variable on CI, Ruffle will stop working on those older browsers. We can use this on CI temporarily as long as we want to keep supporting those browsers.

[danielhjacobs]

We had wanted to wait for a wasm-bindgen update, but rustwasm/wasm-bindgen#4213 was replaced by rustwasm/wasm-bindgen#4235, which only disables reference type transformations for the bundler target (and updates CI to Rust v1.82). rustwasm/wasm-bindgen#4227 was closed as not planned. On that issue, daxpedda suggested wasm32v1-none. I pointed to #18412. daxpedda said

Arc and Mutex should be replaced with Rc and RefCell unless you are using multi-threading. HashMap can be replaced with hashbrown and so on.
If Ruffle intends to continue supporting older versions of Safari with newer versions of Rust and therefore LLVM, it should definitely consider supporting wasm32v1-none.

However, getting wgpu no_std compatible would require quite some work, and I don't know about other dependencies.

With that in mind, we're back to the issue of either using nightly Rust, or dropping support for Safari versions 15 or below and Pale Moon

daxpedda doesn't want to disable the transformations because:

disabling those would only be a temporary solution, e.g. if multi-value gets properly enabled by LLVM it would be emitted by Rust and not wasm-bindgen. This will continue as more and more proposals will be enabled by default which older versions of Safari don't support.

[torokati44]

or dropping support for Safari versions 15 or below and Pale Moon

The former will only get less and less relevant over time, while the latter may (?) end up having this support added...?

[danielhjacobs]

If we're dropping support for Safari 15 officially, there's an extra consideration we haven't talked about. All the current features are Safari 16+, right? Do we need dual-wasm then?

[torokati44]

Interestingly, if we go the nightly route (which I'm not a fan of, BTW) the -Z build-std=std,panic_abort options would also be fairly beneficial for the build with extensions enabled, because a lot of naive memcpy-ing and memset-ing in std (in Vec for instance, while decoding videos) would be a lot faster using the bulk-memory extension.

[danielhjacobs]

while the latter may (?) end up having this support added

That's down to whether https://repo.palemoon.org/MoonchildProductions/UXP/issues/2647 gets fixed. Also worth considering, although I said "all the current features are Safari 16+", I don't know which other ones are unsupported by Pale Moon.

[danielhjacobs]

The former will only get less and less relevant over time

The general consensus is that this should at most be a temporary solution. macOS Catalina and iPhone models 7 and below can't upgrade to Safari 16+. Do we have any ideas on market share there?

[danielhjacobs]

It's impossible to know market shares for macOS:

https://gs.statcounter.com/os-version-market-share/macos/desktop/worldwide
https://bugs.webkit.org/show_bug.cgi?id=216593

[danielhjacobs]

Downloaded this as a CSV, did some calculations:

https://gs.statcounter.com/os-version-market-share/ios/mobile-tablet/worldwide

"Percent of iOS supported" represents what percent of iOS users Ruffle currently supports.
"Percent iOS supported without iOS 14" represents what percent of iOS users Ruffle would support with reference-types enabled if it worked on Safari 15 as it should.
"Percent iOS supported without iOS 14-15" represents what percent of iOS users Ruffle supports with reference-types enabled since it doesn't seem to work on Safari 15, at least for wgpu.
"Percent iOS 16.4+" represents what percent of iOS users can use the WASM module with extensions.

Month	Percent iOS 14(.1+)	Percent iOS 15	Percent iOS 16	Percent iOS 17	Percent iOS 18	Percent of iOS supported	Percent iOS supported without iOS 14	Percent iOS supported without iOS 14-15	Percent iOS 16.0-3	Percent iOS 16.4+
2023-10	2.22	9.94	65.87	18.11	0	96.14	93.92	83.98	14.4	69.58
2023-11	1.95	9.56	54.09	30.74	0	96.34	94.39	84.83	13.38	71.45
2023-12	1.76	9.16	30.61	54.45	0	95.98	94.22	85.06	12.31	72.75
2024-01	1.7	8.82	27.16	58.34	0	96.02	94.32	85.5	11.33	74.17
2024-02	1.72	9.1	23.74	61.41	0	95.97	94.25	85.15	10.27	74.88
2024-03	1.61	8.88	20.79	64.66	0	95.94	94.33	85.45	9.3	76.15
2024-04	1.48	8.39	18.89	67.26	0	96.02	94.54	86.15	8.48	77.67
2024-05	1.35	7.77	16.77	70.46	0	96.35	95	87.23	7.59	79.64
2024-06	1.3	7.24	15.45	72.06	0.27	96.32	95.02	87.78	7	80.78
2024-07	1.41	7.19	14.29	72.59	0.66	96.14	94.73	87.54	6.39	81.15
2024-08	1.4	6.75	13.35	73.5	1.05	96.05	94.65	87.9	5.99	81.91
2024-09	1.02	6.31	12.14	69.46	7.15	96.08	95.06	88.75	5.41	83.34
2024-10	0.86	5.41	10.76	55.92	20.28	93.23	92.37	86.96	4.73	82.23

[torokati44]

I guess linking this here couldn't hurt: https://blog.rust-lang.org/2024/09/24/webassembly-targets-change-in-default-target-features.html#disabling-on-by-default-webassembly-proposals

[danielhjacobs]

Pale Moon logs this when I log individual extension support:

WebAssembly extension "Bulk Memory" is NOT supported.
WebAssembly extension "SIMD" is NOT supported.
WebAssembly extension "Saturated Float-to-Int" is NOT supported.
WebAssembly extension "Sign Extensions" is supported.  
WebAssembly extension "Reference Types" is NOT supported.

Also, when I add multiValue, it logs WebAssembly extension "MultiValue" is NOT supported.

diff --git a/web/packages/core/src/load-ruffle.ts b/web/packages/core/src/load-ruffle.ts
index 6b474f61a..f0aadac41 100644
--- a/web/packages/core/src/load-ruffle.ts
+++ b/web/packages/core/src/load-ruffle.ts
@@ -35,15 +35,31 @@ async function fetchRuffle(
     setPolyfillsOnLoad();
 
     // NOTE: Keep this list in sync with $RUSTFLAGS in the CI build config!
-    const extensionsSupported: boolean = (
-        await Promise.all([
-            bulkMemory(),
-            simd(),
-            saturatedFloatToInt(),
-            signExtensions(),
-            referenceTypes(),
-        ])
-    ).every(Boolean);
+    const extensions = [
+        { name: "Bulk Memory", check: bulkMemory },
+        { name: "SIMD", check: simd },
+        { name: "Saturated Float-to-Int", check: saturatedFloatToInt },
+        { name: "Sign Extensions", check: signExtensions },
+        { name: "Reference Types", check: referenceTypes },
+    ];
+
+    const extensionsSupport = await Promise.all(
+        extensions.map(async (extension) => ({
+            name: extension.name,
+            supported: await extension.check(),
+        }))
+    );
+
+    let extensionsSupported = true;
+
+    extensionsSupport.forEach(({ name, supported }) => {
+        if (!supported) {
+            console.log(`WebAssembly extension "${name}" is NOT supported.`);
+            extensionsSupported = false;
+        } else {
+            console.log(`WebAssembly extension "${name}" is supported.`);
+        }
+    });
 
     if (!extensionsSupported) {
         console.log(

[danielhjacobs]

Note that in testing, iOS 16.3 and below don't work with Rust 1.82+ without this workaround, so it's not just iOS 15-.

[danielhjacobs]

The idea is the following commands should work in CI:

rustup install nightly-2024-12-02
rustup target add wasm32-unknown-unknown --toolchain nightly-2024-12-02
BUILD_WASM_MVP=1 NIGHTLY_VERSION=2024-12-02 npm run build:repro

[danielhjacobs]

It appears that following the most recent wasm-bindgen update this PR is only necessary on browsers which do not have reference-types support. From what I know, of the browsers we currently support, that only eliminates support for Safari 14.1, Pale Moon, and Basilisk.

Pale Moon and Basilisk can currently support Flash anyway. On sites which use the polyfill they won't use Ruffle. Sites which use the Ruffle API or sites which use the polyfill if the user hasn't installed Flash will break on those browsers without this PR if we bump Rust back to stable. We can merge #18838 to add an appropriate error message.

Safari 14.1 on iOS has an ~1% market share among iOS users.