Building wasm32 without wasm-bindgen

[anderspitman]

Been loving working with Slint. Awesome product.

I'm working on porting Slint to a custom WASM runtime. The runtime only provides the most basic functionality like providing event inputs and output via a framebuffer.

I tried building my app with --target wasm32-unknown-unknown. It builds (after setting default-features = false, features = ["compat-1-2", "std"]), but fails to run because it's expecting a bunch of wasm-bindgen imports that don't exist in my runtime.

Is there a way to build Slint for wasm without using wasm-bindgen, or are they tightly coupled?

I tried building for wasm32-wasip1 and that resulting in a lot fewer imports, which I might be able to stub out, but I'd prefer to get it working completely freestanding.

[tronical]

Depending on the symbols in question, perhaps we can make their dependency optional. Could it be that those are console related?

Perhaps you could try building without std? The software renderer should still work in such an environment.

[anderspitman]

Here are the symbols:

"__wbindgen_placeholder__" "__wbindgen_describe"
"__wbindgen_externref_xform__" "__wbindgen_externref_table_grow"
"__wbindgen_externref_xform__" "__wbindgen_externref_table_set_null"
"__wbindgen_placeholder__" "__wbindgen_throw"
"__wbindgen_placeholder__" "__wbg_naturalWidth_2d1cd85377acd810"
"__wbindgen_placeholder__" "__wbg_naturalHeight_1effe4454cdc755f"
"__wbindgen_placeholder__" "__wbg_log_eba0ae95ba1c11a3"

Looks like maybe the last one is console related? I'm not familiar with wasm-bindgen.

I did manage to build it as no_std, but the above symbols are still in there. Here's my minimal no_std setup:

Cargo.toml:

[package]
name = "slint-wasm"
version = "0.1.0"
edition = "2024"

[lib]
crate-type = ["cdylib"]

[dependencies]
slint = { path = "/path/to/forked/slint", version = "1.11.0", default-features = false, features = ["compat-1-2", "libm", "unsafe-single-threaded"]}

[build-dependencies]
slint-build = "1.11.0"

src/lib.rs:

#![no_std]

slint::include_modules!();

I had to make a small patch to slint for this to work. You can see the commit here: master...anderspitman:slint:wasm-freestanding