From dc6b430bc7c0467eb9c6fbedbd889d7a89c3481c Mon Sep 17 00:00:00 2001
From: Jeroen Ooms <jeroenooms@gmail.com>
Date: Thu, 11 Jun 2026 00:33:18 +0200
Subject: [PATCH] Fix wasm build

---
 .github/workflows/wasm.yml | 3 +++
 Cargo.toml                 | 4 ++++
 src/c_api.rs               | 2 +-
 src/collector.rs           | 6 +++---
 src/lib.rs                 | 2 +-
 src/wasm.rs                | 3 ++-
 6 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/wasm.yml b/.github/workflows/wasm.yml
index 6690897..0522383 100644
--- a/.github/workflows/wasm.yml
+++ b/.github/workflows/wasm.yml
@@ -14,6 +14,9 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
+    - name: Setup emscripten
+      uses: mymindstorm/setup-emsdk@v14
+
     - name: Prepare cargo tests
       run: |
         rustup target add wasm32-unknown-emscripten --toolchain=nightly
diff --git a/Cargo.toml b/Cargo.toml
index 46b7ae3..87ed25a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -45,6 +45,10 @@ yuv = { version = "0.1.9", optional = true }
 wasm-bindgen = { version = "0.2.108", optional = true }
 web-sys = {version="0.3.85", features = ["console"], optional = true }
 console_error_panic_hook = {version = "0.1.7", optional = true}
+
+# Only for browser wasm (wasm-pack). Requires RUSTFLAGS with +atomics,+bulk-memory.
+# Not used on wasm32-unknown-emscripten, where rayon uses pthreads instead.
+[target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dependencies]
 wasm-bindgen-rayon = "1.3.0"
 
 [dependencies.ffmpeg]
diff --git a/src/c_api.rs b/src/c_api.rs
index cb676c4..1272be1 100644
--- a/src/c_api.rs
+++ b/src/c_api.rs
@@ -221,7 +221,7 @@ pub unsafe extern "C" fn gifski_add_fixed_color(handle: *mut GifskiHandle, col_r
 ///
 /// Returns 0 (`GIFSKI_OK`) on success, and non-0 `GIFSKI_*` constant on error.
 #[no_mangle]
-#[cfg(feature = "png")]
+#[cfg(all(feature = "png", not(all(target_arch = "wasm32", target_os = "unknown"))))]
 pub unsafe extern "C" fn gifski_add_frame_png_file(handle: *const GifskiHandle, frame_number: u32, file_path: *const c_char, presentation_timestamp: f64) -> GifskiError {
     if file_path.is_null() {
         return GifskiError::NULL_ARG;
diff --git a/src/collector.rs b/src/collector.rs
index 513ed1e..56c3b7c 100644
--- a/src/collector.rs
+++ b/src/collector.rs
@@ -9,14 +9,14 @@ pub use rgb::{RGB8, RGBA8};
 use crate::error::GifResult;
 use crossbeam_channel::Sender;
 
-#[cfg(feature = "png")]
+#[cfg(all(feature = "png", not(all(target_arch = "wasm32", target_os = "unknown"))))]
 use std::path::PathBuf;
 
 pub(crate) enum FrameSource {
     Pixels(ImgVec<RGBA8>),
     #[cfg(feature = "png")]
     PngData(Vec<u8>),
-    #[cfg(all(feature = "png", not(target_arch = "wasm32")))]
+    #[cfg(all(feature = "png", not(all(target_arch = "wasm32", target_os = "unknown"))))]
     Path(PathBuf),
 }
 
@@ -102,7 +102,7 @@ impl Collector {
     /// If the first frame doesn't start at pts=0, the delay will be used for the last frame.
     ///
     /// If this function appears to be stuck after a few frames, it's because [`crate::Writer::write()`] is not running.
-    #[cfg(feature = "png")]
+    #[cfg(all(feature = "png", not(all(target_arch = "wasm32", target_os = "unknown"))))]
     pub fn add_frame_png_file(&self, frame_index: usize, path: PathBuf, presentation_timestamp: f64) -> GifResult<()> {
         self.queue.send(InputFrame {
             frame: FrameSource::Path(path),
diff --git a/src/lib.rs b/src/lib.rs
index 41e707e..0301aa6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -631,7 +631,7 @@ impl Writer {
                             .map_err(|err| Error::PNG(format!("Can't load PNG: {err}")))?;
                         Img::new(image.buffer, image.width, image.height)
                     },
-                    #[cfg(feature = "png")]
+                    #[cfg(all(feature = "png", not(all(target_arch = "wasm32", target_os = "unknown"))))]
                     FrameSource::Path(path) => {
                         let image = lodepng::decode32_file(&path)
                             .map_err(|err| Error::PNG(format!("Can't load {}: {err}", path.display())))?;
diff --git a/src/wasm.rs b/src/wasm.rs
index e2f68ca..c2c8f76 100644
--- a/src/wasm.rs
+++ b/src/wasm.rs
@@ -95,7 +95,8 @@ impl GifskiWasm {
     }
 }
 
-// thread pool for wasm-bindgen-rayon
+// thread pool for wasm-bindgen-rayon (browser wasm only; emscripten uses pthreads)
+#[cfg(all(target_arch = "wasm32", target_os = "unknown"))]
 #[wasm_bindgen]
 pub fn init_thread_pool(num_threads: usize) -> Result<(), JsValue> {
     wasm_bindgen_rayon::init_thread_pool(num_threads);