c768d1d48e
This adds a callback (set by `Context::set_request_repaint_callback`) which integration can use to wake up the UI thread. eframe (egui_web and egui_glow) will use this, replacing `epi::Frame::request_repaint`. Existing code calling `epi::Frame::request_repaint` should be changed to instead call `egui::Context::request_repaint`. This is the first callback added to the egui API, which otherwise is completely driven by data. The purpose of this is to remove the confusion between the two `request_repaint` methods (by removing one). Furthermore, it makes `epi::Frame` a lot simpler, allowing future simplifications to it (perhaps no longer having it be `Send+Sync+Clone`).
63 lines
2.2 KiB
Rust
63 lines
2.2 KiB
Rust
#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
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use eframe::{egui, epi};
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use egui_extras::RetainedImage;
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use poll_promise::Promise;
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fn main() {
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let options = eframe::NativeOptions::default();
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eframe::run_native(Box::new(MyApp::default()), options);
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}
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#[derive(Default)]
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struct MyApp {
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/// `None` when download hasn't started yet.
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promise: Option<Promise<ehttp::Result<RetainedImage>>>,
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}
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impl epi::App for MyApp {
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fn name(&self) -> &str {
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"Download and show an image with eframe/egui"
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}
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fn update(&mut self, ctx: &egui::Context, _frame: &epi::Frame) {
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let promise = self.promise.get_or_insert_with(|| {
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// Begin download.
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// We download the image using `ehttp`, a library that works both in WASM and on native.
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// We use the `poll-promise` library to communicate with the UI thread.
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let ctx = ctx.clone();
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let (sender, promise) = Promise::new();
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let request = ehttp::Request::get("https://picsum.photos/seed/1.759706314/1024");
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ehttp::fetch(request, move |response| {
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let image = response.and_then(parse_response);
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sender.send(image); // send the results back to the UI thread.
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ctx.request_repaint(); // wake up UI thread
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});
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promise
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});
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egui::CentralPanel::default().show(ctx, |ui| match promise.ready() {
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None => {
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ui.add(egui::Spinner::new()); // still loading
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}
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Some(Err(err)) => {
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ui.colored_label(egui::Color32::RED, err); // something went wrong
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}
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Some(Ok(image)) => {
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image.show_max_size(ui, ui.available_size());
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}
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});
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}
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}
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fn parse_response(response: ehttp::Response) -> Result<RetainedImage, String> {
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let content_type = response.content_type().unwrap_or_default();
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if content_type.starts_with("image/") {
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RetainedImage::from_image_bytes(&response.url, &response.bytes)
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} else {
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Err(format!(
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"Expected image, found content-type {:?}",
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content_type
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))
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}
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}
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