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Implement support for Uint8ClampedArray

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This commit implements support for binding APIs that take
`Uint8ClampedArray` in JS. This is pretty rare but comes up in a
`web-sys` binding or two, and we're now able to bind these APIs instead
of having to omit the bindings.

The `Uint8ClampedArray` type is bound by using the `Clamped` marker
struct in Rust. For example this is declaring a JS API that takes
`Uint8ClampedArray`:

    use wasm_bindgen::Clamped;

    #[wasm_bindgen]
    extern {
        fn takes_clamped(a: Clamped<&[u8]>);
    }

The `Clamped` type currently only works when wrapping the `&[u8]`, `&mut
[u8]`, and `Vec<u8>` types. Everything else will produce an error at
`wasm-bindgen` time.

Closes #421
This commit is contained in:
Alex Crichton
2018-09-24 13:49:12 -07:00
parent d10ca579e4
commit 7b495468f6
15 changed files with 169 additions and 60 deletions
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37
examples/julia_set/src/lib.rs
View File

@ -1,24 +1,10 @@
extern crate js_sys;
extern crate wasm_bindgen;
extern crate web_sys;
use std::ops::Add;
use wasm_bindgen::JsCast;
use wasm_bindgen::Clamped;
use wasm_bindgen::prelude::*;
use web_sys::CanvasRenderingContext2d;
use js_sys::{WebAssembly, Uint8ClampedArray};
// Unfortunately `web-sys` at this time doesn't bind APIs with
// `Uint8ClampedArray`. For more information see rustwasm/wasm-bindgen#421.
//
// For now we just bind it ourselves and do some manual frobbing below.
#[wasm_bindgen]
extern "C" {
type ImageData;
#[wasm_bindgen(constructor)]
fn new(arr: &Uint8ClampedArray, width: u32, height: u32) -> ImageData;
}
use web_sys::{CanvasRenderingContext2d, ImageData};
#[wasm_bindgen]
pub fn draw(
@ -30,22 +16,9 @@ pub fn draw(
) -> Result<(), JsValue> {
// The real workhorse of this algorithm, generating pixel data
let c = Complex { real, imaginary, };
let data = get_julia_set(width, height, c);
// And now that we've got some pixels, let's create an `ImageData` with the
// pixels and then ship it off to the canvas.
//
// See notes in the `wasm-in-wasm` example for why this is a bit dangerous
let my_memory = wasm_bindgen::memory()
.dyn_into::<WebAssembly::Memory>()
.unwrap();
let uint8_array = Uint8ClampedArray::new(&my_memory.buffer())
.subarray(
data.as_ptr() as u32,
data.as_ptr() as u32 + data.len() as u32,
);
let data = ImageData::new(&uint8_array, width, height);
ctx.put_image_data(data.unchecked_ref(), 0.0, 0.0)
let mut data = get_julia_set(width, height, c);
let data = ImageData::new_with_u8_clamped_array_and_sh(Clamped(&mut data), width, height)?;
ctx.put_image_data(&data, 0.0, 0.0)
}
fn get_julia_set(width: u32, height: u32, c: Complex) -> Vec<u8> {