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[Feature Request] Available in WebAssembly within web worker #482
Description
What is the feature ?
I'd like use plotters wasm in the web worker, but the plotters/src/style/font/web.rs estimate_layout method use the window. Worker has any window context.
(Optional) Why this feature is useful and how people would use the feature ?
- Improving rendering efficiency when multiple charts are present.
- I prefer performing heavy data processing in a worker and, once the data processing is complete, invoking the chart within the worker instead of sending the chart data back to the main thread.
(Optional) Additional Information
I have implemented a simple version of it，it worked for me. (base the plotters 0.3.5)
// plotters/src/style/font/web.rs
fn estimate_layout(&self, size: f64, text: &str) -> Result<LayoutBox, Self::ErrorType> {
let canvas = OffscreenCanvas::new(300, 300).unwrap();
let context = canvas
.get_context("2d")
.ok()
.unwrap()
.unwrap()
.dyn_into::<OffscreenCanvasRenderingContext2d>()
.unwrap();
context.set_font(&format!("{}px {}", size, self.0));
context.fill_text(&text, 0.0, 0.0);
let bbox = context.measure_text(&text).unwrap();
let width = bbox.width();
let ascent = bbox.font_bounding_box_ascent();
let descent = bbox.font_bounding_box_descent();
let height = (descent - ascent).abs();
// let window = window().unwrap();
// let document = window.document().unwrap();
// let body = document.body().unwrap();
// let span = document.create_element("span").unwrap();
// span.set_text_content(Some(text));
// span.set_attribute("style", &format!("display: inline-block; font-family:{}; font-size: {}px; position: fixed; top: 100%", self.0, size)).unwrap();
// let span = span.into();
// body.append_with_node_1(&span).unwrap();
// let elem = JsCast::dyn_into::<HtmlElement>(span).unwrap();
// let height = elem.offset_height() as i32;
// let width = elem.offset_width() as i32;
// elem.remove();
Ok(((0, 0), (width as i32, height as i32)))
}[target.'cfg(all(target_arch = "wasm32", not(target_os = "wasi")))'.dependencies.web-sys]
version = "0.3.64"
features = [
"Document",
"DomRect",
"Element",
"HtmlElement",
"Node",
"Window",
"HtmlCanvasElement",
"CanvasRenderingContext2d",
# new add
"OffscreenCanvas",
"OffscreenCanvasRenderingContext2d",
"TextMetrics",
]
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