#front-end #macro #closures

macro wasm_extra_macros

Macros for wasm_extra crate

2 releases

0.1.1 Feb 21, 2023
0.1.0 Feb 21, 2023

#129 in #frontend

25 downloads per month
Used in wasm_extra

MIT/Apache

11KB
138 lines

wasm_extra_macros

Latest Version Downloads Documentation License Dependency Status

Macros for wasm_extra.

So far, crate offers two things:

  • the add_event_listener_with_callback! macro named after the ::web_sys::EventTarget::add_event_listener_with_callback() function and which internally uses ::wasm_bindgen::closure::Closure::new() to obtain JavaScript closure from Rust closure.

  • the add_event_listener_with_fn_once_callback! macro, which internally uses ::wasm_bindgen::closure::Closure::once_into_js() for handling FnOnce closures.

The macro is a bit more ergonomic to use and code with it is easier to mentally parse than the corresponding code without it.

side-by-side comparison of the macro and the function

In the expanded code, the event target (open_files_btn) appears only on line 16, whereas in the macro it's the very first argument, which then followed by the event name, then the "closure prologue", and - lastly - the closure itself.

"Closure prologue" is a stipulative term for the code that is executed before the closure itself. It's useful for preparing the closure's environment, for example, by cloning the variables before capturing.

In the code above it's empty but in the following example it's not:

example of the closure prologue

In addition, in the code above the event target is captured by the closure. This requires special handling and is done with the ampersand before the event target's variable.

SemVer Policy

At the moment, there's no any semver guarantees. The crate is being inactively developed.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Dependencies

~1.5MB
~36K SLoC